Sample records for mgso4 contact ion-pairs

  1. Gaz Phase IR and UV Spectroscopy of Neutral Contact Ion Pairs

    Habka, Sana; Brenner, Valerie; Mons, Michel; Gloaguen, Eric


    Cations and anions, in solution, tend to pair up forming ion pairs. They play a crucial role in many fundamental processes in ion-concentrated solutions and living organisms. Despite their importance and vast applications in physics, chemistry and biochemistry, they remain difficult to characterize namely because of the coexistence of several types of pairing in solution. However, an interesting alternative consists in applying highly selective gas phase spectroscopy which can offer new insights on these neutral ion pairs. Our study consists in characterizing contact ion pairs (CIPs) in isolated model systems (M+, Ph-(CH2)n-COO- with M=Li, Na, K, Rb, Cs, and n=1-3), to determine their spectral signatures and compare them to ion pairs in solution. We have used laser desorption to vaporize a solid tablet containing the desired salt. Structural information for each system was obtained by mass-selective, UV and IR laser spectroscopy combined with high level quantum chemistry calculations1. Evidence of the presence of neutral CIPs was found by scanning the π-π* transition of the phenyl ring using resonant two-photon ionization (R2PI). Then, conformational selective IR/UV double resonance spectra were recorded in the CO2- stretch region for each conformation detected. The good agreement between theoretical data obtained at the BSSE-corrected-fullCCSD(T)/dhf-TZVPP//B97-D3/dhf-TZVPP level and experimental IR spectra led us to assign the 3D structure for each ion pair formed. Spectral signatures of (M+, Ph-CH2-COO-) pairs, were assigned to a bidentate CIPs between the alkali cation and the carboxylate group. In the case of (Li+, Ph-(CH2)3-COO-) pairs, the presence of a flexible side chain promotes a cation-π interaction leading to a tridentate O-O-π structure with its unique IR and UV signatures. IR spectra obtained on isolated CIPs were found very much alike the ones published on lithium and sodium acetate in solution2. However, in the case of sodium acetate, solution

  2. Contact ion pair formation between hard acids and soft bases in aqueous solutions observed with 2DIR spectroscopy.

    Sun, Zheng; Zhang, Wenkai; Ji, Minbiao; Hartsock, Robert; Gaffney, Kelly J


    The interaction of charged species in aqueous solution has important implications for chemical, biological, and environmental processes. We have used 2DIR spectroscopy to study the equilibrium dynamics of thiocyanate chemical exchange between free ion (NCS(-)) and contact ion pair configurations (MNCS(+)), where M(2+) = Mg(2+) or Ca(2+). Detailed studies of the influence of anion concentration and anion speciation show that the chemical exchange observed with the 2DIR measurements results from NCS(-) exchanging with other anion species in the first solvation shell surrounding Mg(2+) or Ca(2+). The presence of chemical exchange in the 2DIR spectra provides an indirect, but robust, determinant of contact ion pair formation. We observe preferential contact ion pair formation between soft Lewis base anions and hard Lewis acid cations. This observation cannot be easily reconciled with Pearson's acid-base concept or Collins' Law of Matching Water Affinities. The anions that form contact ion pairs also correspond to the ions with an affinity for water and protein surfaces, so similar physical and chemical properties may control these distinct phenomena.

  3. Structure of MgSO4 in Concentrated Aqueous Solutions by X-Ray Diffraction

    CAO Ling-di; FANG Yan; FANG Chun-hui


    Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X'pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function(RDF). The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function(DRDF). The calculation of the geometric model shows that octahedrally six-coordinated Mg(H2O)62+, with an Mg2+…Ow bond length of 0.201 nm dominates in the solutions. There exists contact ion-pair(CIP) in the more concentrated solution(1:18, H2O/salt molar ratio) with a coordination number of 0.8 and a characteristic Mg…S distance of 0.340 nm. The result indicates the hydrated SO42ion happens in the solution. The S…Ow bond distance was determined to be 0.382 nm with a coordination number of 13. The fraction of CIP increases significantly with the increasing concentration. The symmetry of the hydration structure of sulfate ion is lowered by forming complex with magnesium ion.

  4. Thermodynamics of Ion Pair of Magnesium Sulfate in Mixed Solvent


    @@ Introduction Magnesium sulfate is an archetypal 2-2 salt that plays a central role in defining the characteristics of higher valent electrolyte solutions and its solution has been widely used to test various theories of strong electrolyte behavior and to develop models of ion association in solution[1]. Up to now, the ion pairs of magnesium sulfate in an aqueous solution have been widely investigated by using different experimental techniques, such as conductometry[2] , cryoscopy[3] , potentiometry[4] ,solubility[5] and Raman spectrometry[6]. However, to our knowledge, no measurement of the standard association constant of the ion pairs, [MgSO4] 0 in a glucosewater mixed solvent is available.

  5. Earliest use of initial prophylactic dose of magnesium sulphate (MgSO4 in severe pre-eclampsia to improve maternal and perinatal outcome, in a rural medical college, WB, India

    Suresh Chandra Mondal


    Conclusions: Initial dose prophylactic magnesium sulphate (MgSO4 the earliest, can prevent both maternal perinatal maternal mortality. So, prophylactic magnesium sulphate (MgSO4 must be started at the first point of contact by trained health providers. [Int J Reprod Contracept Obstet Gynecol 2014; 3(3.000: 653-655

  6. Physicochemical Properties of Ion Pairs of Biological Macromolecules.

    Iwahara, Junji; Esadze, Alexandre; Zandarashvili, Levani


    Ion pairs (also known as salt bridges) of electrostatically interacting cationic and anionic moieties are important for proteins and nucleic acids to perform their function. Although numerous three-dimensional structures show ion pairs at functionally important sites of biological macromolecules and their complexes, the physicochemical properties of the ion pairs are not well understood. Crystal structures typically show a single state for each ion pair. However, recent studies have revealed the dynamic nature of the ion pairs of the biological macromolecules. Biomolecular ion pairs undergo dynamic transitions between distinct states in which the charged moieties are either in direct contact or separated by water. This dynamic behavior is reasonable in light of the fundamental concepts that were established for small ions over the last century. In this review, we introduce the physicochemical concepts relevant to the ion pairs and provide an overview of the recent advancement in biophysical research on the ion pairs of biological macromolecules.

  7. Na+ Cl- ion pair association in water-DMSO mixtures: Effect of ion pair model potentials



    Potentials of Mean Force (PMF) for the Na+ Cl- ion pair in water–dimethyl sulfoxide (DMSO)mixtures for three DMSO mole fractions have been computed using constrained Molecular Dynamics (MD)simulations and confirmed by dynamical trajectories and residence times of the ion pair at various inter-ionicseparations. The three ion-ion direct potentials used are 12-6-1, exp-6-1 and exp-8-6-1. The physical picturethat emerges is that there is a strong contact ion pair (CIP) and strong to moderate solvent separated ion pair(SSIP) in these solutions. Analysis of local ion clusters shows that ions are dominantly solvated by watermolecules. The 12-6-1 potential model predicts running coordination numbers closest to experimental data.

  8. The ternary system K2SO4MgSO4CaSO4

    Rowe, J.J.; Morey, G.W.; Silber, C.C.


    Melting and subsolidus relations in the system K2SO4MgSO4CaSO4 were studied using heating-cooling curves, differential thermal analysis, optics, X-ray diffraction at room and high temperatures and by quenching techniques. Previous investigators were unable to study the binary MgSO4CaSO4 system and the adjacent area in the ternary system because of the decomposition of MgSO4 and CaSO4 at high temperatures. This problem was partly overcome by a novel sealed-tube quenching method, by hydrothermal synthesis, and by long-time heating in the solidus. As a result of this study, we found: (1) a new compound, CaSO4??3MgSO4 (m.p. 1201??C) with a field extending into the ternary system; (2) a high temperature form of MgSO4 with a sluggishly reversible inversion. An X-ray diffraction pattern for this polymorphic form is given; (3) the inversion of ??-CaSO4 (anhydrite) to ??-CaSO4 at 1195??C, in agreement with grahmann; (1) (4) the melting point of MgSO4 is 1136??C and that of CaSO4 is 1462??C (using sealed tube methods to prevent decomposition of the sulphates); (5) calcium langbeinite (K2SO4??2CaSO4) is the only compound in the K2SO4CaSO4 binary system. This resolved discrepancies in the results of previous investigators; (6) a continuous solid solution series between congruently melting K2SOP4??2MgSO4 (langbeinite) and incongruently melting K2SO4??2CaSO4 (calcium langbeinite); (7) the liquidus in the ternary system consists of primary phase fields of K2SO4, MgSO4, CaSO4, langbeinite-calcium langbeinite solid solution, and CaSO4??3MgSO4. The CaSO4 field extends over a large portion of the system. Previously reported fields for the compounds (K2SO4??MgSO4??nCaSO4), K2SO4??3CaSO4 and K2SO4??CaSO4 were not found; (8) a minimum in the ternary system at: 740??C, 25% MgSO4, 6% CaSO4, 69% K2SO4; and ternary eutectics at 882??C, 49% MgSO4, 19% CaSO4, 32% K2SO4; and 880??, 67??5% MgSO4, 5% CaSO4, 27??5% K2SO4. ?? 1967.

  9. High-resolution Measurement of Contact Ion-pair Structures in Aqueous RbCl Solutions from the Simultaneous Corefinement of their Rb and Cl K-edge XAFS and XRD Spectra

    Pham, Van-Thai; Fulton, John L.


    In concentrated solutions of aqueous RbCl, all of the Rb+ and Cl- ions exist as contact ion pairs. This full structural assessment is derived from the refinement of three independent experimental measurements: the Rb and Cl K-edge x-ray absorption fine structure (XAFS) and the x-ray diffraction spectra (XRD). This simultaneous refinement of the XAFS and XRD data provides high accuracy since each method probes the structure of different local regions about the ions with high sensitivity. At high RbCl concentration (6 m (mol/kg )) the solution is dominated by Rb+ - Cl- contact ion pairs yielding an average of 1.5 pairs at an Rb-Cl distance of 3.24 Å. Upon formation of these ion pairs, approximately 1.1 waters molecules are displaced from the Rb+ and 1.4 water molecules from Cl-. The hydration shells about both the cation and anion are also determined. These results greatly improve the understanding of monovalent ions and provide a basis for testing the Rb+-Cl- interaction potentials used in molecular dynamics (MD) simulation. This research was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences.

  10. Ion Pairing in Alkali Nitrate Electrolyte Solutions.

    Xie, Wen Jun; Zhang, Zhen; Gao, Yi Qin


    In this study, we investigate the thermodynamics of alkali nitrate salt solutions, especially the formation of contact ion pairs between alkali cation and nitrate anion. The ion-pairing propensity shows an order of LiNO3 activity coefficients and suggest that the empirical "law of matching water affinity" is followed by these alkali nitrate salt solutions. The spatial patterns of contact ion pairs are different in the three salt solutions studied here: Li(+) forms the contact ion pair with only one oxygen of the nitrate while Na(+) and K(+) can also be shared by two oxygens of the nitrate. In reproducing the salt activity coefficient using Kirkwood-Buff theory, we find that it is essential to include electronic polarization for Li(+) which has a high charge density. The electronic continuum correction for nonpolarizable force field significantly improves the agreement between the calculated activity coefficients and their experimental values. This approach also improves the performance of the force field on salt solubility. From these two aspects, this study suggests that electronic continuum correction can be a promising approach to force-field development for ions with high charge densities.

  11. Water Transport in MgSO4·7H2O during Dehydration in View of Thermal Storage

    Donkers, P.A.J.; Beckert, S.; Pel, L.; Stallmach, F.; Steiger, M.; Adan, O.C.G.


    The water phases in a MgSO4·7H2O crystal during heating were studied with the help of NMR. The thermogravimetric analysis (TGA) data showed that the heating rate has a strong effect on the dehydration process. NMR experiments showed that pore water, i.e., an aqueous solution of MgSO4, was produced d

  12. Isothermal equation of state and high-pressure phase transitions of synthetic meridianiite (MgSO4·11D2O) determined by neutron powder diffraction and quasielastic neutron spectroscopy

    Fortes, A. Dominic; Fernandez-Alonso, Felix; Tucker, Matthew; Wood, Ian G.


    We have collected neutron powder diffraction data from MgSO4·11D2O (the deuterated analogue of meridianiite), a highly hydrated sulfate salt that is thought to be a candidate rock-forming mineral in some icy satellites of the outer solar system. Our measurements, made using the PEARL/HiPr and OSIRIS instruments at the ISIS neutron spallation source, covered the range 0.1 < P < 800 MPa and 150 < T < 280 K. The refined unit-cell volumes as a function of P and T are parameterized in the form of a Murnaghan integrated linear equation of state having a zero-pressure volume V 0 = 706.23 (8) Å3, zero-pressure bulk modulus K 0 = 19.9 (4) GPa and its first pressure derivative, K′ = 9 (1). The structure’s compressibility is highly anisotropic, as expected, with the three principal directions of the unit-strain tensor having compressibilities of 9.6 × 10−3, 3.4 × 10−2 and 3.4 × 10−3 GPa−1, the most compressible direction being perpendicular to the long axis of a discrete hexadecameric water cluster, (D2O)16. At high pressure we observed two different phase transitions. First, warming of MgSO4·11D2O at 545 MPa resulted in a change in the diffraction pattern at 275 K consistent with partial (peritectic) melting; quasielastic neutron spectra collected simultaneously evince the onset of the reorientational motion of D2O molecules with characteristic time-scales of 20–30 ps, longer than those found in bulk liquid water at the same temperature and commensurate with the lifetime of solvent-separated ion pairs in aqueous MgSO4. Second, at ∼ 0.9 GPa, 240 K, MgSO4·11D2O decomposed into high-pressure water ice phase VI and MgSO4·9D2O, a recently discovered phase that has hitherto only been formed at ambient pressure by quenching small droplets of MgSO4(aq) in liquid nitrogen. The fate of the high-pressure enneahydrate on further compression and warming is not clear from the neutron diffraction data, but its occurrence

  13. Simultaneous determination of 11 fluorescent whitening agents in food-contact paper and board by ion-pairing high-performance liquid chromatography with fluorescence detection.

    Jiang, Dingguo; Chen, Lisong; Fu, Wusheng; Qiu, Hanquan


    4,4'-Diaminostilbene-2,2'-disulfonic acid based fluorescent whitening agents (DSD-FWAs) are prohibited in food-contact paper and board in many countries. In this work, a reliable high-performance liquid chromatography method was developed for the simultaneous determination of 11 common DSD-FWAs in paper material. Sample preparation and extraction as well as chromatographic separation of multicomponent DSD-FWAs were successfully optimized. DSD-FWAs in prepared samples were ultrasonically extracted with acetonitrile/water/triethylamine (40:60:1, v/v/v), separated on the C(18) column with the mobile phase containing tetrabutylammonium bromide, and then detected by a fluorescence detector. The limits of detection were 0.12-0.24 mg/kg, and the calibration curves showed the linear correlation (R(2) ≥ 0.9994) within the range of 8.0-100 ng/mL, which was equivalent to the range of 0.80-10 mg/kg in the sample. The average recoveries and the RSDs were 81-106% and 2-9% at two fortification levels (1.0 and 5.0 mg/kg) in paper bowls, respectively. The successful determination of 11 DSD-FWAs in food-contact paper and board obtained from local markets indicated that the newly developed method was rapid, accurate, and highly selective.




    Full Text Available Thin film nanocomposite (TFN membrane with graphene oxide (GO embedded into the polyamide (PA selective top layer has been developed for salt removal. 0.1 wt% of GO were dispersed in the trimesoyl chloride (TMC organic solution and incorporated into the PA layer during interfacial polymerization with piperazine. The fabricated TFN membrane was characterized in terms of the membrane morphological structure and surface hydrophilicity. The divalent magnesium sulfate (MgSO4 salt removal performance of the TFN was evaluated and compared with the thin film composite (TFC counterpart. The surface morphology of the TFN membranes was altered and the surface hydrophilicity was increased with the presence of GO. The incorporation of GO has improved the permeate water flux, in which maximum improvement of 140% compared to that of TFC has been obtained, without sacrificing much on the salt rejection properties. Although further investigation is required, this study has experimentally verified the potential application of GO to heighten the salt separation performance of TFN membranes.

  15. Simulation experiments on the reaction system of CH4-MgSO4-H2O

    DING KangLe; LI ShuYuan; YUE ChangTao; ZHONG NingNing


    H2S-rich gas in carbonate reservoirs is usually attributed to thermochemical sulfate reduction (TSR). In this paper, thermal simulation experiments on the reaction system of CH4-MgSO4-H2O were carried out using autoclave at 425℃-525℃. The threshold temperature for initiating TSR is much lower than our previous studies (550℃). Properties of the reaction products were analyzed by microcoulometry, gas-chromatography (GC), Fourier transform-infrared spectrometry (FT-IR) and X-ray diffraction (XRD) methods. Thermodynamics and reaction kinetics of TSR processes were investigated on the basis of the experimental data. The results show that thermochemical reduction of magnesium sulfate with methane can proceed spontaneously to produce magnesium oxide, hydrogen sulfur, and carbon diox-ide as the main products, and high temperature is thermodynamically favorable to the reaction. Ac-cording to the reaction model, the calculated activation energy of TSR is 101.894 kJ/mol, which is lower than that by most previous studies. Mg2+ may have played a role of catalytic action in the process of TSR. The elementary steps of TSR and reaction mechanism were discussed tentatively. The study can provide important information on the explanation of geochemical depth limit for natural gas and on the generation of high H2S gas in deep carbonates reservoirs.

  16. Meridianiite (MgSO4-11H2O): A New Mineral Species Observed on Earth and Predicted to Exist on Mars

    Peterson, R. C.; Nelson, W.; Madu, B.; Shurvell, H. F.


    Meridianiite, MgSO4-11H2O, was recently discovered on the surface of a frozen pond in central British Columbia, Canada. Meridianiite is stable below 2°C. Above 2°C it melts incongruently to a slurry of epsomite (MgSO4-7H2O) and water.

  17. Sensitivity of the mayfly Adenophlebia auriculata (Ephemeroptera: Leptophlebiidae) to MgSO4 and Na2SO4

    Vellemu, E. C.; Mensah, P. K.; Griffin, N. J.; Odume, O. N.


    Acid mine drainage (AMD) continues to deteriorate water quality in freshwater ecosystems. Sulphates, a major salt component in AMD, can exacerbate AMD effects in freshwater because salts are toxic to aquatic life in high concentrations. Sulphates are predominant in South African AMD impacted freshwater ecosystems. In this study, the sensitivity of nymphs of the mayfly Adenophlebia auriculata (Ephemeroptera: Leptophlebiidae) was investigated by exposing the organisms to magnesium sulphate (MgSO4) and sodium sulphate (Na2SO4) as models of mining salinisation in short-term (96 h) and long-term (240 h) in static system tests. Short-term and long-term lethal concentrations of each salt were estimated using regression analyses. The results indicated that A. auriculata was more sensitive to MgSO4 (LC50 = 3.81 g/L) than Na2SO4 (LC50 = 8.78 g/L) after short-term exposures. However, this species became sensitive to Na2SO4 (LC10 = 0.19 g/L) but tolerant to MgSO4 (LC10 = 0.35 g/L) after long-term exposures. These results suggest that the 0.25 g/L sulphate compliance limit for South Africa is inadequate to protect A. auriculata from Na2SO4 toxicity in the long-term, yet it overprotects this species from MgSO4 exposures in the short-term. The findings of this study are an important major step in understanding the ecological effects of AMD to aquatic life.

  18. Photosynthetic capacity, nutrient status and growth of maize (Zea mays L. upon MgSO4 leaf-application

    Mareike eJezek


    Full Text Available The major plant nutrient magnesium is involved in numerous physiological processes and its deficiency can severely reduce the yield and quality of crops. Since Mg availability in soil and uptake into the plant is often limited by unfavorable soil or climatic conditions, application of Mg onto leaves, the site with highest physiological Mg demand, might be a reasonable alternative fertilization strategy. This study aimed to investigate, if MgSO4 leaf-application in practically relevant amounts can efficiently alleviate the effects of Mg starvation in maize, namely reduced photosynthesis capacity, disturbed ion homeostasis and growth depression. Results clearly demonstrated that Mg deficiency could be mitigated by MgSO4 leaf-application as efficiently as by resupply of MgSO4 via the roots in vegetative maize plants. Significant increases in SPAD values and net rate of CO2-assimilation as well as enhanced shoot biomass have been achieved. Ion analysis furthermore revealed an improvement of the nutrient status of Mg-deficient plants with regard to [Mg], [K] and [Mn] in distinct organs, thereby reducing the risk of Mn-toxicity at the rootside, which often occurs together with Mg deficiency on acid soils. In conclusion, foliar fertilization with Mg proved to be an efficient strategy to adequately supply maize plants with magnesium and might hence be of practical relevance to correct nutrient deficiencies during the growing season.

  19. Photosynthetic capacity, nutrient status, and growth of maize (Zea mays L.) upon MgSO4 leaf-application.

    Jezek, Mareike; Geilfus, Christoph-Martin; Bayer, Anne; Mühling, Karl-Hermann


    The major plant nutrient magnesium (Mg) is involved in numerous physiological processes and its deficiency can severely reduce the yield and quality of crops. Since Mg availability in soil and uptake into the plant is often limited by unfavorable soil or climatic conditions, application of Mg onto leaves, the site with highest physiological Mg demand, might be a reasonable alternative fertilization strategy. This study aimed to investigate, if MgSO4 leaf-application in practically relevant amounts can efficiently alleviate the effects of Mg starvation in maize, namely reduced photosynthesis capacity, disturbed ion homeostasis and growth depression. Results clearly demonstrated that Mg deficiency could be mitigated by MgSO4 leaf-application as efficiently as by resupply of MgSO4 via the roots in vegetative maize plants. Significant increases in SPAD values and net rate of CO2-assimilation as well as enhanced shoot biomass have been achieved. Ion analysis furthermore revealed an improvement of the nutrient status of Mg-deficient plants with regard to [Mg], [K], and [Mn] in distinct organs, thereby reducing the risk of Mn-toxicity at the rootside, which often occurs together with Mg deficiency on acid soils. In conclusion, foliar fertilization with Mg proved to be an efficient strategy to adequately supply maize plants with Mg and might hence be of practical relevance to correct nutrient deficiencies during the growing season.

  20. Direct contact vs. solvent-shared ion pairs in nicl2 electrolytesmonitored by multiplet effects at the ni(ii) l-edge x-ray absorptionDOC_XNOTE=Published by BESSY, Germany in collaboration with LawrenceBerkeley National Laboratory staff.

    Aziz, E.F.; Eisebitt, S.; Eberhardt, W.; de Groot, F.; Chiou,J.W.; Dong, C.L.; Guo, J.-H.


    We investigate the local electronic structure in aqueous NiCl{sub 2} electrolytes by Ni L edge x-ray absorption spectroscopy. The experimental findings are interpreted in conjunction with multiplet calculations of the electronic structure and the resulting spectral shape. In contrast to the situation in the solid, the electronic structure in the electrolyte reflects the absence of direct contact Ni-Cl ion pairs. We observe a systematic change of the intensity ratio of singlet and triplet-related spectral features as a function of electrolyte concentration. These changes can be described theoretically by a changed weight of transition matrix contributions with different symmetry. We interpret these findings as being due to progressive distortions of the local symmetry induced by solvent-shared ion pairs.

  1. Marcus Theory of Ion-Pairing

    Roy, Santanu; Baer, Marcel D.; Mundy, Christopher J.; Schenter, Gregory K.


    We present a theory for ion pair dissociation and association, motivated by the concepts of the Marcus theory of electron transfer. Despite the extensive research on ion-pairing in many chemical and biological processes, much can be learned from the exploration of collective reaction coordinates. To this end, we explore two reaction coordinates, ion pair distance and coordination number. The study of the correlation between these reaction coordinates provides a new insight into the mechanism and kinetics of ion pair dissociation and association in water. The potential of mean force on these 2D-surfaces computed from molecular dynamics simulations of different monovalent ion pairs reveal a Marcus-like mechanism for ion-pairing: Water molecules rearrange forming an activated coordination state prior to ion pair dissociation or association, followed by relaxation of the coordination state due to further water rearrangement. Like Marcus theory, we find the existence of an inverted region where the transition rates are slower with increasing exergonicity. This study provides a new perspective for the future investigations of ion-pairing and transport. SR, CJM, and GKS were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. MDB was supported by MS3 (Materials Synthesis and Simulation Across Scales) Initiative, a Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory (PNNL). The research was performed using PNNL Institutional Computing. PNNL is a multi-program national laboratory operated by Battelle for the U.S. Department of Energy.

  2. Review Article Ion-paired Drug Delivery: An Avenue for ...


    Aug 9, 2011 ... application of ion paired system to delivery of drugs through various routes of ... octanol/water partition coefficient of the ion pairs ... Physical stability of these preparations .... complex was lyophilized and directly encapsulated.

  3. Identification of Ion-Pair Structures in Solution by Vibrational Stark Effects.

    Hack, John; Grills, David C; Miller, John R; Mani, Tomoyasu


    Ion pairing is a fundamental consideration in many areas of chemistry and has implications in a wide range of sciences and technologies that include batteries and organic photovoltaics. Ions in solution are known to inhabit multiple possible states, including free ions (FI), contact ion pairs (CIP), and solvent-separated ion pairs (SSIP). However, in solutions of organic radicals and nonmetal electrolytes, it is often difficult to distinguish between these states. In the first part of this work, we report evidence for the formation of SSIPs in low-polarity solvents and distinct measurements of CIP, SSIP, and FI, by using the ν(C≡N) infrared (IR) band of a nitrile-substituted fluorene radical anion. Use of time-resolved IR detection following pulse radiolysis allowed us to unambiguously assign the peak of the FI. In the presence of nonmetal electrolytes, two distinct red-shifted peaks were observed and assigned to the CIP and SSIP. The assignments are interpreted in the framework of the vibrational Stark effect (VSE) and are supported by (1) the solvent dependence of ion-pair populations, (2) the observation of a cryptand-separated sodium ion pair that mimics the formation of SSIPs, and (3) electronic structure calculations. In the second part of this work, we show that a blue-shift of the ν(C≡N) IR band due to the VSE can be induced in a nitrile-substituted fluorene radical anion by covalently tethering it to a metal-chelating ligand that forms an intramolecular ion pair upon reduction and complexation with sodium ion. This adds support to the conclusion that the shift in IR absorptions by ion pairing originates from the VSE. These results combined show that we can identify ion-pair structures by using the VSE, including the existence of SSIPs in a low-polarity solvent.

  4. Molecular mechanisms of decomposition of hydrated Na+Cl- ion pairs under planar nanopore conditions

    Shevkunov, S. V.


    The decomposition of Na+Cl- ion pairs under the conditions of a nanoscopic planar pore with structureless walls in a material contact with water vapor at 298 K is simulated by Monte Carlo method. The transition from the state of a contact ion pair (CIP) to the state of solvent-separated ion pair (SSIP) is shown to occur as a result of an increase in the vapor pressure over a pore after exceeding the threshold number of molecules in a hydrate shell. It is found that the planar form of a molecular cluster under the conditions of a narrow pore does not level an abrupt structural transition and the formation of hydrogen bonds in the hydrate shell starts after three molecules are added. The hydrogen bond length under pore conditions is found to be resistant to variations in the hydrate shell size and coincides with that in water under normal conditions.

  5. Hydrogen bonding mediated ion pairs of some aprotic ionic liquids and their structural transition in aqueous solution

    Huiyong Wang; Miao Liu; Yuling Zhao; Xiaopeng Xuan; Yang Zhao; Jianji Wang


    Ion pair speciation of ionic liquids (ILs) has an important effect on the physical and chemical properties of ILs and recognition of the structure of ion pairs in solution is essential.It has been reported that ion pairs of some ILs can be formed by hydrogen bonding interactions between cations and anions of them.Considering the fact that far-IR (FIR) spectroscopy is a powerful tool in indicating the intermolecular and intramolecular hydrogen bonding,in this work,this spectroscopic technique has been combined with molecular dynamic (MD) simulation and nuclear magnetic resonance hydrogen spectroscopy (1H NMR) to investigate ion pairs ofaprotic ILs [Bmim][NO3],[BuPy][NO3],[Pyr14][NO3],[PP14][NO3] and [Bu-choline][NO3] in aqueous IL mixtures.The FIR spectra have been assigned with the aid of density functional theory (DFT) calculations,and the results are used to understand the effect of cationic nature on the structure of ion pairs.It is found that contact ion pairs formed in the neat aprotic ILs by hydrogen bonding interactions between cation and anion,were still maintained in aqueous solutions up to high water mole fraction (say 0.80 for [BuPy] [NO3]).When water content was increased to a critical mole fraction of water (say 0.83 for [BuPy] [NO3]),the contact ion pairs could be transformed into solvent-separated ion pairs due to the formation of the hydrogen bonding between ions and water.With the further dilution of the aqueous ILs solution,the solvent-separated ion pairs was finally turned into free cations and free anions (fully hydrated cations or anions).The concentrations of the ILs at which the contact ion pairs were transformed into solvent-separated ion pairs and solvent-separated ion pairs were transformed into free ions (fully hydrated ion) were dependent on the cationic structures.These information provides direct spectral evidence for ion pair structures of the aprotic ILs in aqueous.solution.MD simulation and 1H NMR results support the conclusion

  6. Solubility measurement and solid-liquid equilibrium model for the ternary system MgBr2 + MgSO4 + H2O at 288.15 K

    Li Dan


    Full Text Available The solubility of magnesium minerals and the refractive index of the ternary system MgBr2 + MgSO4 + H2O at 288.15 K were investigated using an isothermal dissolution method. It was found that there are two invariant points in the phase diagram and the solubility isotherm of this ternary system consists of three branches, corresponding to equilibrium crystallization of Epsomite (MgSO4·7H2O, Eps, hexahydrite (MgSO4·6H2O, Hex and magnesium bromide hexahydrate (MgBr2·6H2O, Mb. Neither solid solutions nor double salts were found. The refractive indices calculated from empirical equation are in good agreement with the experimental data. Combining the results from solubility measurements with the single-salt parameters for MgBr2 and MgSO4, and the mixed ion-interaction parameter θBr,S0(4, the parameter ψMg,Br,S0(4 at 288.15 K was fitted using the Pitzer theory and Harvie-Weare (HW approach. In addition, the average equilibrium constants of the stable equilibrium solids at 288.15 K were obtained by a method using the activity product constant. A chemical model, which combined the Pitzer parameters and the average equilibrium constants, was constructed to calculate the solid + liquid equilibria in the ternary system MgBr2 + MgSO4 + H2O at 288.15 K. The model agreed well with the equilibrium solubility data for the magnesium salts.

  7. A comparison of amorphous calcium carbonate crystallization in aqueous solutions of MgCl2 and MgSO4: implications for paleo-ocean chemistry

    Han, Mei; Zhao, Yanyang; Zhao, Hui; Han, Zuozhen; Yan, Huaxiao; Sun, Bin; Meng, Ruirui; Zhuang, Dingxiang; Li, Dan; Liu, Binwei


    Based on the terminology of "aragonite seas" and "calcite seas", whether different Mg sources could affect the mineralogy of carbonate sediments at the same Mg/Ca ratio was explored, which was expected to provide a qualitative assessment of the chemistry of the paleo-ocean. In this work, amorphous calcium carbonate (ACC) was prepared by direct precipitation in anhydrous ethanol and used as a precursor to study crystallization processes in MgSO4 and MgCl2 solutions having different concentrations at 60 °C (reaction times 240 and 2880 min). Based on the morphology of the aragonite crystals, as well as mineral saturation indices and kinetic analysis of geochemical processes, it was found that these crystals formed with a spherulitic texture in 4 steps. First, ACC crystallized into columnar Mg calcite by nearly oriented attachment. Second, the Mg calcite changed from columnar shapes into smooth dumbbell forms. Third, the Mg calcite transformed into rough dumbbell or cauliflower-shaped aragonite forms by local dissolution and precipitation. Finally, the aragonite transformed further into spherulitic radial and irregular aggregate forms. The increase in Ca2+ in the MgSO4 solutions compared with the MgCl2 solutions indicates the fast dissolution and slow precipitation of ACC in the former solutions. The phase transition was more complete in the 0.005 M MgCl2 solution, whereas Mg calcite crystallized from the 0.005 M MgSO4 solution, indicating that Mg calcite could be formed more easily in an MgSO4 solution. Based on these findings, aragonite and Mg calcite relative to ACC could be used to provide a qualitative assessment of the chemistry of the paleo-ocean. Therefore, calcite seas relative to high-Mg calcite could reflect a low concentration MgSO4 paleo-ocean, while aragonite seas could be related to an MgCl2 or high concentration of MgSO4 paleo-ocean.

  8. Ion pairs of indobenzimidazolo cyanines: a structural study based on conductivity, absorption, fluorescence and 1H-NMR

    Tatikolov, Aleksandr S.; Ishchenko, Aleksandr A.; Ghelli, Stefano; Ponterini, Glauco


    Asymmetric benzimidazolo carbo, di- and tricarbocyanines form ion pairs of the solvent-separated and contact types with different counterions in tetrahydrofuran, toluene and toluene-nitrile mixtures. The dissociation constants of the ion pairs in tetrahydrofuran, evaluated from conductivity data, do not depend on the length of the polymethine chain and show only a small decrease with decreasing counterion size. The absorption and fluorescence excitation spectra of the contact ion pairs exhibit a pronounced hypsochromic shift with respect to the solvated ions and the solvent-separated ion pairs. 1H-NMR experiments have provided information about the electronic structures of the ions of both the asymmetric dyes and the corresponding symmetric carbocyanines. They have also revealed different preferred anion locations in the contact ion pairs of the symmetric indocarbocyanine on one hand, and of the benzimidazolo carbocyanine and the asymmetric dyes on the other. This structural difference is suggested to be a cause of the observed opposite effects of ion pairing on the isomerization kinetics of the two groups of dyes.

  9. Molecular Dynamics Simulation of Na(+)-Cl(-) Ion-Pair in Water-Methanol Mixtures under Supercritical and Ambient Conditions.

    Keshri, Sonanki; Sarkar, Atanu; Tembe, B L


    Constrained molecular dynamics simulations have been performed to investigate the structure and thermodynamics of Na(+)-Cl(-) ion-pair association in water-methanol mixtures under supercritical and ambient conditions in dilute solutions. From the computed potentials of mean force (PMFs) we find that contact ion pairs (CIPs) are more stable than all other associated states of the ion pairs in both ambient and supercritical conditions. Stabilities of CIPs increase with increase in the mole fraction of methanol. In supercritical conditions, major changes in PMFs occur as we go from x(methanol) = 0.00 to x(methanol) = 0.50. The stable solvent shared ion pair (SShIP) which occurs in x(methanol) = 0.00 and 0.25, vanishes when x(methanol) is 0.50 or greater. The stabilities of these ion pairs increase with increasing temperature. Local structures around the ions are studied using the radial distribution functions, density profiles, angular distribution functions, running coordination numbers and excess coordination numbers. Preferential solvation analysis shows that both Na(+) and Cl(-) ions are preferentially solvated by water. From the calculation of enthalpies and entropies, we find that Na(+)-Cl(-) ion-pair association in water-methanol binary mixtures is endothermic and driven by entropy both in ambient as well as under supercritical conditions.

  10. TDDFT study of the polarity controlled ion-pair separation in an excited-state proton transfer reaction.

    Liu, Yu-Hui; Mehata, Mohan Singh; Lan, Sheng-Cheng


    6-Hydroxyquinoline (6HQ) is an ideal photoacid system for exploring excited-state proton transfer (ESPT) reactions. We have previously (Mahata et al. (2002)) shown that the ESPT reaction between 6HQ and trimethylamine (TMA) leads to an "unusual" emission in the 440-450 nm range, containing two decay components (∼5 ns and ∼12 ns). The observed results suggest the presence of a contact ion-pair and a solvent separated ion-pair. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been employed to study the nature of the contact ion-pair formed between 6HQ and TMA and to determine why the decay component ∼12 ns is absent in a non-polar solvent. Calculations of the hydrogen-bonded complexes formed between 6HQ and TMA and its ESPT reaction product, namely 6HQ-TMA and 6HQ-TMA-PT, respectively, have been carried out, both in the electronic ground and excited states. Moreover, by using the CPCM model, different dielectric constants have been introduced into the calculations. On increasing the dielectric constant, the hydrogen bond in 6HQ-TMA-PT becomes weaker and the hydrogen bond length becomes larger; this effectively facilitates the proton transfer reaction and formation of separated ion-pair. Thus, the separation and diffusion of the contact ion-pair can be controlled by changing the polarity of the surroundings.

  11. Properties of CO2 clathrate hydrates formed in the presence of MgSO4 solutions with implications for icy moons

    Safi, E.; Thompson, S. P.; Evans, A.; Day, S. J.; Murray, C. A.; Parker, J. E.; Baker, A. R.; Oliveira, J. M.; van Loon, J. Th.


    Context. There is evidence to suggest that clathrate hydrates have a significant effect on the surface geology of icy bodies in the solar system. However the aqueous environments believed to be present on these bodies are likely to be saline rather than pure water. Laboratory work to underpin the properties of clathrate hydrates in such environments is generally lacking. Aims: We aim to fill this gap by carrying out a laboratory investigation of the physical properties of CO2 clathrate hydrates produced in weak aqueous solutions of MgSO4. Methods: We use in situ synchrotron X-ray powder diffraction to investigate clathrate hydrates formed at high CO2 pressure in ice that has formed from aqueous solutions of MgSO4 with varying concentrations. We measure the thermal expansion, density and dissociation properties of the clathrates under temperature conditions similar to those on icy solar system bodies. Results: We find that the sulphate solution inhibits the formation of clathrates by lowering their dissociation temperatures. Hysteresis is found in the thermal expansion coefficients as the clathrates are cooled and heated; we attribute this to the presence of the salt in solution. We find the density derived from X-ray powder diffraction measurements is temperature and pressure dependent. When comparing the density of the CO2 clathrates to that of the solution in which they were formed, we conclude that they should sink in the oceans in which they form. We also find that the polymorph of ice present at low temperatures is Ih rather than the expected Ic, which we tentatively attribute to the presence of the MgSO4. Conclusions: We (1) conclude that the density of the clathrates has implications for their behaviour in satellite oceans as their sinking and floating capabilities are temperature and pressure dependent; (2) conclude that the presence of MgSO4 inhibits the formation of clathrates and in some cases may even affect their structure and (3) report the dominance of Ih throughout the experimental procedure despite Ic being the stable phase at low temperature.

  12. Amphiphilic organic ion pairs in solution: a theoretical study.

    Pradines, Vincent; Poteau, Romuald; Pimienta, Veronique


    The macroscopic manifestation of hydrophobic interactions for amphiphilic organic ion pairs (tetraalkylammonium-anion) has been shown experimentally by measuring their association constants and their affinity with the organic phase. Beyond a certain size, there is a direct relation between association constants and chain lengths in tetraalkylammonium ions. We propose to cast a bridge between these results and geometrical properties considered at the level of a single ion pair by means of quantum chemistry calculations performed on model systems: trimethylalkylammonium-pentyl sulfate instead of tetraalkylammonium-dodecyl sulfate. Two limiting cases are considered: head-to-head configurations, which yield an optimal electrostatic interaction between polar heads, and parallel configurations with a balance between electrostatic and hydrophobic interactions. All properties (geometries, complexation energies, and atomic charges) were obtained at the MP2 level of calculation, with water described by a continuum model (CPCM). Dispersion forces link hydrocarbon chains of tetraalkylammonium ions and pentyl sulfate, thus yielding (for the largest ion pairs) parallel configurations favored with respect to head-to-head geometries by solute-solvent electrostatic interactions. Given the small experimental association energies, we probe the accuracy limit of the MP2 and CPCM methods. However, clear trends are obtained as a function of chain length, which agree with the experimental observations. The calculated monotonic stabilization of ion pairs when the hydrocarbon chain increases in length is discussed in terms of electrostatic interactions (between ions and between ion pairs and water), dispersion forces, and cavitation energies.

  13. Extraction mechanism of monovalent ion-pairs by polyurethane foams.

    Fong, P; Chow, A


    The extractability sequence of K(+) approximately Rb(+) > Cs(+) > Na(+) > Li(+) for the extraction with polyether foam suggests that the cation chelation mechanism might be operative. However, the same order was obtained for the extraction with 100% polypropylene oxide polyether foam which does not normally adopt a helical structure to form oxygen-rich cavities as easily or as effectively as polyethylene oxide to accommodate alkali metal ions. This result indicates that a hole-size/cation-diameter relationship may not be required for the high extraction of K(+). The extraction of alkali metal DPAs and hydroxides from methanol demonstrates the importance of the solvent effect. It indicates that the water-structure enforced ion-pairing (WSEIP) is the driving force for extraction of the ion-pairs. The extraction mechanism for ionic species can be described as an ion-pair extraction process. The overall effect of ion-pair formation in water and interaction of the extracted ions with foam appears to determine the extractability of the ions of the extractable ion-pair.

  14. Quantum Dynamics of Radical-Ion-Pair Reactions

    Kominis, I K


    Radical-ion-pair reactions were recently shown to represent a rich biophysical laboratory for the application of quantum measurement theory methods and concepts, casting doubt on the validity of the theoretical treatment of these reactions and the results thereof that has been at the core of spin chemistry for several decades now. The ensued scientific debate, although exciting, is plagued with several misconceptions. We will here provide a comprehensive treatment of the quantum dynamics of radical-ion-pair reactions, generalizing our recent work and elaborating on the analogy with the double-slit experiment having partial "which-path" information. This analogy directly leads to the general treatment of radical-ion pair reactions covering the whole range between the two extremes, that of perfect singlet-triplet coherence and that of complete incoherence.

  15. Bisguanidinium dinuclear oxodiperoxomolybdosulfate ion pair-catalyzed enantioselective sulfoxidation

    Zong, Lili; Wang, Chao; Moeljadi, Adhitya Mangala Putra; Ye, Xinyi; Ganguly, Rakesh; Li, Yongxin; Hirao, Hajime; Tan, Choon-Hong


    Catalytic use of peroxomolybdate for asymmetric transformations has attracted increasing attention due to its catalytic properties and application in catalysis. Herein, we report chiral bisguanidinium dinuclear oxodiperoxomolybdosulfate [BG]2+[(μ-SO4)Mo2O2(μ-O2)2(O2)2]2- ion pair, as a catalyst for enantioselective sulfoxidation using aqueous H2O2 as the terminal oxidant. The ion pair catalyst is isolatable, stable and useful for the oxidation of a range of dialkyl sulfides. The practical utility was illustrated using a gram-scale synthesis of armodafinil, a commercial drug, with the catalyst generated in situ from 0.25 mol% of bisguanidinium and 2.5 mol% of Na2MoO4.2H2O. Structural characterization of this ion pair catalyst has been successfully achieved using single-crystal X-ray crystallography.

  16. Bisguanidinium dinuclear oxodiperoxomolybdosulfate ion pair-catalyzed enantioselective sulfoxidation

    Zong, Lili; Wang, Chao; Moeljadi, Adhitya Mangala Putra; Ye, Xinyi; Ganguly, Rakesh; Li, Yongxin; Hirao, Hajime; Tan, Choon-Hong


    Catalytic use of peroxomolybdate for asymmetric transformations has attracted increasing attention due to its catalytic properties and application in catalysis. Herein, we report chiral bisguanidinium dinuclear oxodiperoxomolybdosulfate [BG]2+[(μ-SO4)Mo2O2(μ-O2)2(O2)2]2− ion pair, as a catalyst for enantioselective sulfoxidation using aqueous H2O2 as the terminal oxidant. The ion pair catalyst is isolatable, stable and useful for the oxidation of a range of dialkyl sulfides. The practical uti...

  17. Water-Mediated Ion Pairing: Occurrence and Relevance

    van der Vegt, Nico F.A.; Haldrup, Kristoffer; Roke, Sylvie


    We present an overview of the studies of ion pairing in aqueous media of the past decade. In these studies, interactions between ions, and between ions and water, are investigated with relatively novel approaches, including dielectric relaxation spectroscopy, far-infrared (terahertz) absorption...... spectroscopy, femtosecond mid-infrared spectroscopy, and X-ray spectroscopy and scattering, as well as molecular dynamics simulation methods. With these methods, it is found that ion pairing is not a rare phenomenon only occurring for very particular, strongly interacting cations and anions. Instead, for many...

  18. Effect of NaHCO3, MgSO4, Sodium Ascorbate, Sodium Glutamate, Phosphate Buffer on Survival of Lactobacillus bulgaricus During Freeze-drying

    He Chen


    Full Text Available In the present study, the experiments were investigated the effects of different concentrations of cryoprotective agents, such as NaHCO3, MgSO4, sodium ascorbate, sodium glutamate, phosphate buffer, respectively, which used on survival of Lactobacillus bulgaricus during freeze drying. The number of viable cells and survival ratio were measured by the plate count method. The results were as follows: cryoprotective agents played important roles in survival of Lactobacillus bulgaricus during freeze drying. When the relative volume of phosphate buffer was 1.5 (v/v, the number of viable cells was highest, while the survival ratio reached highest, the concentration of sodium ascorbate was 4.5%.


    Thomsen, Mohens; Willumsen, Dorthe


    A procedure for quantitative ion-pair extraction of 4(5)-methylimidazole from caramel colour using bis(2-ethylhexyl)phosphoric acid as ion-pairing agent has been developed. Furthermore, a reversed-phase ion-pair liquid chromatographic separation method has been established to analyse the content ...

  20. Ion pairs in non-redundant protein structures

    B A Gowri Shankar; R Sarani; Daliah Michael; P Mridula; C Vasuki; G Sowmiya; B Vasundhar; P Sudha; J Jeyakanthan; D Velmurugan; K Sekar


    Ion pairs contribute to several functions including the activity of catalytic triads, fusion of viral membranes, stability in thermophilic proteins and solvent–protein interactions. Furthermore, they have the ability to affect the stability of protein structures and are also a part of the forces that act to hold monomers together. This paper deals with the possible ion pair combinations and networks in 25% and 90% non-redundant protein chains. Different types of ion pairs present in various secondary structural elements are analysed. The ion pairs existing between different subunits of multisubunit protein structures are also computed and the results of various analyses are presented in detail. The protein structures used in the analysis are solved using X-ray crystallography, whose resolution is better than or equal to 1.5 Å and R-factor better than or equal to 20%. This study can, therefore, be useful for analyses of many protein functions. It also provides insights into the better understanding of the architecture of protein structure.

  1. Interactions in ion pairs of protic ionic liquids: comparison with aprotic ionic liquids.

    Tsuzuki, Seiji; Shinoda, Wataru; Miran, Md Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi


    The stabilization energies for the formation (E(form)) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G** level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E(form) for the [dema][CF3SO3] and [dmpa][CF3SO3] complexes (-95.6 and -96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF3SO3] complex (-81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl(-), BF4(-), TFSA(-) anions. The anion has contact with the N-H bond of the dema(+) or dmpa(+) cations in the most stable geometries of the dema(+) and dmpa(+) complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0-18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E(form) for the less stable geometries for the dema(+) and dmpa(+) complexes are close to those for the most stable etma(+) complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N-H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA(-) anion, while the strong directionality of the interactions was not suggested from the simulation of the [etma][CF3SO3] ionic liquid.

  2. Quantum Dynamics of Radical-Ion-Pair Reactions

    Kominis, I. K.


    Radical-ion-pair reactions were recently shown to represent a rich biophysical laboratory for the application of quantum measurement theory methods and concepts, casting doubt on the validity of the theoretical treatment of these reactions and the results thereof that has been at the core of spin chemistry for several decades now. The ensued scientific debate, although exciting, is plagued with several misconceptions. We will here provide a comprehensive treatment of the quantum dynamics of r...

  3. Ion Pairs or Neutral Molecule Adducts? Cooperativity in Hydrogen Bonding

    DeKock, Roger L.; Schipper, Laura A.; Dykhouse, Stephanie C.; Heeringa, Lee P.; Brandsen, Benjamin M.


    We performed theoretical studies on the systems NH[subscript 3] times HF times mH[subscript 2]O, NH[subscript 3] times HCl times mH[subscript 2]O, with m = 0, 1, 2, and 6. The molecules with m = 0 form hydrogen-bonded adducts with little tendency to form an ion-pair structure. The molecule NH[subscript 3] times HCl times H[subscript 2]O cannot be…

  4. Enantiomeric Separation of Amino Alcohols by Ion-pair Chromatography


    Enantiomers of four amino alcohols were resolved by ion-pair chromatography with (+)-10-camphorsulphonic acid as chiral counter ion. Studies of the influence of the mobile phase composition, the solute structure and the mobile phase flow-rate on separation are presented. Under the optimized conditions, enantiomeric propranolol, norephedrine, metropolol and salbutamol were separated using dichloromethane -1-pentanol (97:3, v/v) as mobile phase on Lichrospher-100-DIOL column.

  5. Conjugation of silica nanoparticles with cellulose acetate/polyethylene glycol 300 membrane for reverse osmosis using MgSO4 solution.

    Sabir, Aneela; Shafiq, Muhammad; Islam, Atif; Jabeen, Faiza; Shafeeq, Amir; Ahmad, Adnan; Zahid Butt, Muhammad Taqi; Jacob, Karl I; Jamil, Tahir


    Thermally-induced phase separation (TIPS) method was used to synthesize polymer matrix (PM) membranes for reverse osmosis from cellulose acetate/polyethylene glycol (CA/PEG300) conjugated with silica nanoparticles (SNPs). Experimental data showed that the conjugation of SNPs changed the surface properties as dense and asymmetric composite structure. The results were explicitly determined by the permeability flux and salt rejection efficiency of the PM-SNPs membranes. The effect of SNPs conjugation on MgSO4 salt rejection was more significant in magnitude than on permeation flux i.e. 2.38 L/m(2)h. FTIR verified that SNPs were successfully conjugated on the surface of PM membrane. DSC of PM-SNPs shows an improved Tg from 76.2 to 101.8 °C for PM and PM-S4 respectively. Thermal stability of the PM-SNPs membranes was observed by TGA which was significantly enhanced with the conjugation of SNPs. The micrographs of SEM and AFM showed the morphological changes and increase in the valley and ridges on membrane surface. Experimental data showed that the PM-S4 (0.4 wt% SNPs) membrane has maximum salt rejection capacity and was selected as an optimal membrane.

  6. Critical concentration of ion-pairs formation in nonpolar media.

    Dukhin, Andrei


    It is known that nonpolar liquids can be ionized by adding surfactants, either ionic or nonionic. Surfactant molecules serve as solvating agents, building inverse micelles around ions, and preventing their association back into neutral molecules. According to the Bjerrum-Onsager-Fuoss theory, these inverse micelle ions should form "ion pairs." This, in turn, leads to nonlinear dependence of the conductivity on the concentration. Surprisingly, ionic surfactants exhibit linear conductivity dependence, which implies that these inverse micelle ions do not form ion pairs. Theory predicts the existence of two ionic strength ranges, which are separated by a certain critical ion concentration. Ionic strength above the critical one is proportional to the square root of the ion concentration, whereas it becomes linear below the critical concentration. Critical ion concentration lies within the range of 10(-11) -10(-7) mol/L when ion size ranges from 1 to 3 nm. Critical ion concentration is related, but not equal, to a certain surfactant concentration (critical concentration of ion-pairs formation (CIPC)) because only a fraction of the surfactant molecules is incorporated into the micelles ions. The linear conductivity dependence for ionic surfactants indicates that the corresponding CIPC is above the range of studied concentrations, perhaps, due to rather large ion size. The same linearity is a sign that charged inverse micelles structure and fraction are concentration independent due to strong charge-dipole interaction in the charge micelle core. This also proves that CIPC is independent of critical concentration of micelle formation. Nonionic surfactants, on the other hand, exhibit nonlinear conductivity dependence apparently due to smaller ion sizes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. On the rogue wave propagation in ion pair superthermal plasma

    Abdelwahed, H. G., E-mail:, E-mail:; Zahran, M. A. [Physics Department, College of Sciences and Humanities Studies Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj (Saudi Arabia); Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt); El-Shewy, E. K., E-mail:; Elwakil, S. A. [Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt)


    Effects of superthermal electron on the features of nonlinear acoustic waves in unmagnetized collisionless ion pair plasma with superthermal electrons have been examined. The system equations are reduced in the form of the nonlinear Schrodinger equation. The rogue wave characteristics dependences on the ionic density ratio (ν = n{sub –0}/n{sub +0}), ionic mass ratio (Q = m{sub +}/m{sub −}), and superthermality index (κ) are investigated. It is worth mentioning that the results present in this work could be applicable in the Earth's ionosphere plasmas.

  8. Ion pair formation in [bmim]I ionic liquids.

    Katoh, Ryuzi; Hara, Mikiya; Tsuzuki, Seiji


    Ion pair formation between [bmim](+) and iodide has been studied in acetonitrile solutions and in ionic liquids. In solution, absorption spectra change remarkably with concentration, indicating the formation of charge transfer (CT) complexes. The shape of CT complex spectra can be explained by ab initio molecular orbital calculations. On the basis of the results from the solution and spectroscopic absorption measurements, we confirmed that CT complexes were formed in neat [bmim]I ionic liquid. High stability of the CT complex is demonstrated by the temperature dependence of near-IR absorption measurements.

  9. Anti-inflammation of MgSO4 on acute pulmonary hypertension%硫酸镁抗急性肺动脉高压的炎症机制

    卢宏志; 高国芹; 李昨飞; 单冰竹


    Objective To investigate the effect and the anti-inflammatory mechanism of magnesium sulfate (MgSO4) on acute pulmonary hypertension.Methods 30 mongrel dogs were randomly divided into five groups:control group,surgical group,MgSO4 7.0 group,MgSO4 8.0 group,and MgSO4 9.0 group.The control group was not given any treatment,and the surgical group was operated to induce acute pulmonary hypertension,and the three MgSO4 groups were given MgSO4 to maintain intravenous concentration with 7.0 mmol/L,8.0 mmol/L,and 9.0 mmol/L respectively after acute pulmonary hypertension.The mean pulmonary artery pressure (MPAP) and circulation mean arterial pressure (MAP) were detected.Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in serum were measured by enzyme-linked immunosorbent assay and radioimmunoassay,monocyte chemoattractant protein-1 (MCP-1) expression in the lung tissue was determined by western blot.Results ①MPAP,TNF-α,IL-6,and MCP 1 protein expression were significantly higher in surgical group than those in control group,and were decreased significantly in MgSO4 7.0 group,MgSO4 8.0 group,and MgSO4 9.0 group with dose dependence.②MAP was significantly lower in surgical group than that in control group.MAP in MgSO4 7.0 group,MgSO4 8.0 group,and MgSO4 9.0 group was significantly increased compared with surgical group and MAP in MgSO4 9.0 group was the highest.Conclusions MgSO4 significantly reduces pulmonary hypertension,which is probably associated with reduction of the inflammatory response by inhibition of MCP-1 expression in lung tissue and decrease of TNF-α and IL-6 in serum.%目的 探讨硫酸镁(MgSO4)对急性肺栓塞肺动脉高压的影响及其抗炎机制.方法 30只雄性杂种犬,体质量(15±2.1) kg,随机分为5组:空白组、对照组以及MgSO47.0组、MgSO48.0组、MgSO4 9.0组,每组6只,其中空白组不给予任何处理;对照组造成急性肺动脉高压;其余三组造成急性肺动脉高压后给予MgSO4静滴,稳定30 min后,MgSO4 200 mg/kg静脉滴注0.5h,然后维持血MgSO4浓度分别为7.0 mmol/L、8.0 mmol/L以及9.0 mmol/L.肺动脉、股动脉插管检测平均肺动脉压(MPAP)、体循环平均动脉压(MAP),应用酶联免疫吸附以及放免法分别测定血清中白介素6(IL-6)和肿瘤坏死因子α(TNF-α),Western blot测定肺组织中单核细胞趋化蛋白-1(MCP-1)蛋白表达.结果 ①对照组MPAP较空白组显著升高(P<0.01),MgSO4 7.0组、MgSO48.0组以及MgSO49.0组MPAP较对照组显著下降(P<0.05或P<0.01),其中MgSO49.0组下降最明显;对照组MAP较空白组显著降低(P <0.05或P<0.01),MgSO4 7.0组、MgSO48.0组以及MgSO49.0组MAP较对照组显著升高(P <0.05或P<0.01),其中MgSO49.0组升高最明显.②对照组血清中TNF-α以及IL-6较空白组升高(P<0.05),MgSO4 7.0组、MgSO4 8.0组以及MgSO4 9.0组TNF-α以及IL-6较对照组显著下降(P<0.05或P<0.01),MgSO4 9.0组下降最明显;③对照组MCP-1蛋白表达较空白组显著升高(P<0.01),MgSO4 7.0组、MgSO4 8.0组以及MgSO49.0组MCP-1蛋白表达较对照组显著下降(P<0.01),MgSO49.0组蛋白表达最低.结论 MgSO4可显著降低肺动脉高压,这可能与其抑制肺组织MCP-1表达,降低TNF-α以及IL-6,从而抑制炎症反应增强有关.

  10. Generalizations of the Fuoss Approximation for Ion Pairing

    Zhu, P; Pratt, L R; Papadopoulos, K D


    An elementary statistical observation identifies generalizations of the Fuoss approximation for the probability distribution function that describes ion clustering in electrolyte solutions. By exploiting measurable inter-ionic correlation functions, this generalization is correct at the closest pair distances, extends beyond primitive electrolyte solution models, and includes non-ionic interactions and solvation effects. The proposed generalization is relevant also for the computational analysis of bi-molecular reactive processes in solution. Comparisons with direct numerical simulation results show that the simplest generalization is accurate for a slightly supersaturated solution of tetraethylammonium tetrafluoroborate in propylene carbonate ([tea][BF4]/PC), and also for a primitive model associated with the [tea][BF4]/PC results. For [tea][BF4]/PC, the atomically detailed results identify solvent-separated nearest-neighbor ion-pairs. This generalization is examined also for the ionic liquid 1-butyl-3-methy...

  11. Method for the preparation of cellulose acetate flat sheet composite membranes for forward osmosis—Desalination using MgSO4 draw solution

    Sairam, M.


    A lab scale method for the preparation of defect free flat sheet composite membranes for forward osmosis (FO) has been developed. Membranes containing a thin layer of cellulose acetate (CA) cast on a nylon fabric of 50μm thick were prepared by phase inversion in water. Cellulose acetate (CA) membranes with an overall thickness of 70-80μm have been prepared with lactic acid, maleic acid and zinc chloride as pore forming agents, at different annealing temperatures, for forward osmosis. These membranes have been tested in the desalination of saline feeds (35g·L-1 of NaCl) using magnesium sulphate solution (150g·L-1) as the draw solution. The water flux, and rejection of NaCl, were compared with those of commercially available membranes tested under the same FO conditions. The commercially available FO membrane from Hydration Technologies Inc, OR (M1) has a permeability of 0.13L·h-1·m-2·bar-1 with a NaCl rejection of 97% when tested with 150g·L-1 of MgSO4 in the draw solution. Another commercially available membrane for FO from Hydration Technologies Inc, OR, M2 has a water permeability of 0.014L·h-1·m-2·bar-1 with NaCl rejection of 100%. The flux and rejection of the CA membranes prepared in this work are found to be dependent on the nature of the pore forming agent, and annealing temperature. Impregnation of an inorganic filler, sodium montmorrillonite in CA membranes and coating of CA membranes with hydrophilic PVA did not enhance the flux of base CA membranes. Cellulose acetate membranes cast from dope solutions containing acetone/isopropanol and lactic acid, maleic acid and zinc chloride as pore forming agents have water permeabilities of 0.13, 0.09 and 0.68L·h-1·m-2·bar-1 respectively, with NaCl rejections of 97.7, 99.3 and 88% when annealed at 50°C. CA membranes prepared with zinc chloride as a pore forming agent have good permeability of 0.27L·h-1·m-2·bar-1 with a NaCl rejection of 95% when annealed at 70°C. © 2011.

  12. An Interface for Sensitive Analysis of Monoamine Neurotransmitters by Ion-Pair Chromatography–ESI-MS with Continuous On-Line Elimination of Ion-Pair Reagents

    Shi,Shuyun; Zhao, Binqing; Yagnik, Gargey; Zhou, Feimeng


    A challenge in coupling ion-pair chromatography (IPC) on-line with electrospray ionization-mass spectrometry (ESI-MS) is that the nonvolatile ion-pair reagent (e.g., alkyl sulfate for amines or tetrabutylammonium for carboxylic acids) in the mobile phase suppresses the ESI-MS signals in the gas phase and their accumulation can clog the MS sampling interface. Consequently, IPC–ESI-MS is conducted either with a volatile ion-pair reagent, which could compromise the analyte separation efficiency,...

  13. Electronic transition dipole moment and radiative lifetime calculations of sodium dimer ion-pair states.

    Sanli, Aydin; Beser, Bediha; Edwardson, John R; Magnier, Sylvie; Ahmed, Ergin H; Marjatta Lyyra, A


    We report here ab initio calculated electronic transition dipole moments for the sodium dimer ion pair states of (1)Σg (+) symmetry. They vary strongly as a function of internuclear distance because of the effect of the Na(+) + Na(-) ion pair potential, which also causes the formation of additional wells and shoulders in the molecular potential energy curves. We also present a computational study of the transition dipole moment matrix elements and lifetimes for these ion-pair states.

  14. Hyaluronic acid ion-pairing nanoparticles for targeted tumor therapy.

    Li, Wenhao; Yi, Xiaoli; Liu, Xing; Zhang, Zhirong; Fu, Yao; Gong, Tao


    Hyaluronic acid (HA)-based doxorubicin (DOX) nanoparticles (HA-NPs) were fabricated via ion-pairing between positively charged DOX and negatively charged HA, which displayed near-spherical shapes with an average size distribution of 180.2nm (PDI=0.184). Next, HA-NPs were encapsulated in liposomal carriers to afford HA-based DOX liposomes (HA-LPs), which also showed near-spherical morphology with an average size of 130.5nm (PDI=0.201). HA-NPs and HA-LPs displayed desirable sustained-release profiles compared to free DOX, and moreover, HA-LPs were proven to prevent premature release of DOX from HA-NPs. Cell based studies demonstrated HA-NPs and HA-LPs were selectively taken up by CD44(+) tumor cells, and DOX was released intracellularly to target the cell nuclei. Both HA-NPs and HA-LPs showed comparable levels of penetration efficiency in tumor spheroids. In vivo studies revealed that HA-NPs and HA-LPs significantly prolonged the blood circulation time of DOX, decreased accumulation in the normal tissues and enriched drugs into the tumors. Furthermore, HA-NPs and HA-LPs greatly enhanced therapeutic efficacy of DOX in tumor-bearing mice and minimized systemic toxicity against vital organs. In sum, HA-NPs and HA-LPs represent promising nanocarriers for CD44(+) tumor-targeted delivery.

  15. Study of the reversible water vapour sorption process of MgSO4.7H2O and MgCl2.6H2O under the conditions of seasonal solar heat storage

    Ferchaud, C. J.; Zondag, H. A.; Veldhuis, J. B. J.; de Boer, R.


    The characterization of the structural, compositional and thermodynamic properties of MgSO4.7H2O and MgCl2.6H2O has been done using in-situ X-ray Diffraction and thermal analyses (TG/DSC) under practical conditions for seasonal heat storage (Tmax=150°C, p(H2O)=13 mbar). This study showed that these two materials release heat after a dehydration/hydration cycle with energy densities of 0.38 GJ/m3 for MgSO4.7H2O and 0.71 GJ/m3 MgCl2.6H2O. The low heat release found for MgSO4.7H2O is mainly attributed to the amorphization of the material during the dehydration performed at 13 mbar which reduces its sorption capacity during the rehydration. MgCl2.6H2O presents a high energy density which makes this material interesting for seasonal heat storage in domestic applications. This material would be able to fulfil the winter heat demand of a passive house estimated at 6 GJ with a packed bed reactor of 8.5 m3. However, a seasonal heat storage system built with this material should be carefully set with a restricted temperature at 40°C for the hydration reaction to avoid the liquefaction of the material at lower temperature which limits its performances for long term storage.

  16. Hydrothermal Synthesis and the Effect of Reaction Time on Morphology of MgSO4 · 5Mg(OH)2 · 3H2O%MgSO4·5Mg(OH)2·3H2O的水热合成及反应时间对其形貌的影响

    朱黎霞; 岳涛; 高世扬; 夏树屏


    Both whisker and nanometer MgSO4 @ 5Mg(OH)2 @ 3H2O(MOS) were prepared by hydrothermal method at140℃ for different times, using NaOH and MgSO4 @ 7H2O as raw materials. The MgSO4 @ 5Mg(OH)2 @ 3H2O part-icles were characterized by powder X-ray diffraction(XRD), thermal analysis(TGA-DSC), infrared spectroscopy(FT-IR), transmission electron microscopy (SEM) and scanning electron microscopy (TEM). The size distribution inwhisker-like and nanocrystalline materials are in the range of 10~50μm and 10~20nm respectively. The whiskerMOS is metastable phase in MgSO4-NaOH-H2O system at 140℃, whereas nanometer MOS is stable phase.

  17. Experimental research of MgSO4 water soluble sand core hardened by twice microwave heating%二次微波加热制备硫酸镁水溶性砂芯试验研究

    何家庆; 樊自田; 刘鑫旺; 刘富初


    Twice microwave heating technology was applied to harden MgSO4 water soluble sand core , and the effect of kaolin reinforcement on properties of the core was tested .The performance character-istics of the MgSO4 water soluble sand core were also analyzed and compared with sodium silicate sand hardened by twice microwave heating technology .Scanning electron microscope (SEM ) was used to investigate the micro-morphology of the MgSO4 water soluble sand core ,and the optimized water sol-uble sand core was applied to cast AZ91D alloy .The results indicate that the MgSO4 water soluble sand core hardened by twice microwave heating technology has advantages of high tensile strength , excellent surface stability ,good humidity resistance ,and high removability by collapsing in the wa-ter ,which has good application prospects .The SEM analysis demonstrates that with the addition of kaolin ,there are less cracks and holes in the binder bridge of the water soluble sand core ,and the mixed-mode fracture mechanism is instead of the cohesive fracture mechanism .%采用二次微波加热工艺制备硫酸镁水溶性砂芯,测试研究了增强剂高岭土对硫酸镁水溶性砂芯性能的影响,对比分析了二次微波加热制备的硫酸镁水溶性砂芯和二次微波硬化水玻璃砂的性能特征,通过扫描电子显微镜(SEM )分析了硫酸镁水溶性砂芯的微观形貌,采用优化配方的硫酸镁水溶性砂芯进行了AZ91D的浇铸试验.试验结果表明:二次微波加热制备的硫酸镁水溶性砂芯具有较高的抗拉强度、表面安定性和抗吸湿性,砂芯铸后的水溶溃散性良好,具有良好的应用前景.SEM分析结果表明:加入高岭土后水溶性砂芯粘结桥中的裂纹和孔隙减少,断裂方式由内聚断裂变成复合断裂.

  18. Distinct dissociation kinetics between ion pairs: Solvent-coordinate free-energy landscape analysis

    Yonetani, Yoshiteru


    Different ion pairs exhibit different dissociation kinetics; however, while the nature of this process is vital for understanding various molecular systems, the underlying mechanism remains unclear. In this study, to examine the origin of different kinetic rate constants for this process, molecular dynamics simulations were conducted for LiCl, NaCl, KCl, and CsCl in water. The results showed substantial differences in dissociation rate constant, following the trend kLiCl constants arose predominantly from the variation in solvent-state distribution between the ion pairs. The formation of a water-bridging configuration, in which the water molecule binds to an anion and a cation simultaneously, was identified as a key step in this process: water-bridge formation lowers the related dissociation free-energy barrier, thereby increasing the probability of ion-pair dissociation. Consequently, a higher probability of water-bridge formation leads to a higher ion-pair dissociation rate.

  19. Interactions in 1-ethyl-3-methyl imidazolium tetracyanoborate ion pair: Spectroscopic and density functional study

    Mao, James X.; Lee, Anita S.; Kitchin, John R.; Nulwala, Hunaid B.; Luebke, David R.; Damodaran, Krishnan


    Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]{sup +}[TCB]{sup -}). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]{sup +}[TCB]{sup -} ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.

  20. Interactions in 1-ethyl-3-methyl imidazolium tetracyanoborate ion pair: Spectroscopic and density functional study

    Mao, James X; Lee, Anita S; Kitchin, John R; Nulwala, Hunaid B; Luebke, David R; Damodaran, Krishnan


    Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]{sup +}[TCB]{sup -}). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]{sup +}[TCB]{sup -} ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.

  1. Vinylimidazole-Based Asymmetric Ion Pair Comonomers: Synthesis, Polymerization Studies and Formation of Ionically Crosslinked PMMA

    Jana, S.; Vasantha, V.A.; Stubbs, L.P.; Parthiban, A.; Vancso, G.J.


    Vinylimidazole-based asymmetric ion pair comonomers (IPCs) which are free from nonpolymerizable counter ions have been synthesized, characterized and polymerized by free radical polymerization (FRP), atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer (R

  2. Infrared Spectra of Simple Inorganic Ion Pairs in Solid Solution: A Physical Inorganic Chemistry Experiment.

    Miller, Philip J.; Tong, William G.


    Presents a physical inorganic experiment in which large single crystals of the alkali halides doped with divalent ion impurities are prepared easily. Demonstrates the ion pairing of inorganic ions in solid solution. (CS)

  3. Chiral metal-dithiolene/viologen ion pairs: synthesis and electrical conductivity.

    Kisch, H; Eisen, B; Dinnebier, R; Shankland, K; David, W I; Knoch, F


    Enantiomerically pure dithiolene complexes NBu4[Ni[(R,R)-diotte)2] and NBu4[Ni((S,S)-diotte]2] (diotte2- = a 1,3-dioxolane-tetrathiaethylene), were prepared from the corresponding enantiomers of a diotte2- precursor. The structure of the precursor was solved by single-crystal X-ray analysis; desulfurization afforded a novel tetrathiafulvalene derivative. Combination of the complex monoanion with the enantiomers of the viologen derivative bis(2-methyl-3-hydroxypropyl)-4,4'-dipyridinium (HiBV2+) afforded enantiomeric and diastereomeric ion-pair complexes of the type HiBV[Ni(diotte)2]2. For comparison, the analogous compounds A[Ni(diotte)2]2, (A2+ = methyl (MV2+), octyl (OV2-), stearyl (StV2+) viologen or two 2,2'-bipyridinium acceptors), HiBV-[Ni(diotte)L] [L = mnt2- (maleonitrile-1,2-dithiolate), dmit2- (2-thioxo-1,3-dithiol-4,5-dithiolate)], MV[Ni(dmit)2)]2, [Ni(diotte)2], and [Ni(diotte)(dmit)] were synthesized. An X-ray powder diffraction structural analysis of MV-[Ni(dmit)2)]2 revealed the presence of mixed stacks that contain the sequence anion-anion-cation. While no short contacts are observable within a stack, these are observed between the stacks for the dication-anion interaction by short S...H distances in the range of 2.77 to 2.86 A, and for the anion-anion interaction short S...S distances of 3.55 to 3.65 A. In agreement with the absence of intrastack interactions, no ion-pair charge-transfer band can be detected in this and the other complexes. ESR and UV/Vis data suggest that in [Ni(diotte)2]- electron delocalization is less pronounced than in the corresponding mnt2- and dmit2- complexes. The specific electrical conductivity (sigma) of pressed powder pellets ranges from 10(-2) to 10(-12) ohm(-1) cm(-1) and in all cases increases with increasing temperature (293 - 393 K) according to an Arrhenius law. Corresponding activation energies vary from 0.14 to 0.93 eV and increase linearly with log a for structurally similar ion pairs. Charge generation is

  4. Radical-ion-pair reactions are the biochemical equivalent of the optical double slit experiment

    Kominis, I. K.


    Radical-ion-pair reactions were recently shown to represent a rich biophysical laboratory for the application of quantum measurement theory methods and concepts. We here show that radical-ion-pair reactions essentially form a non-linear biochemical double slit interferometer. Quantum coherence effects are visible when "which-path" information is limited, and the incoherent limit is approached when measurement-induced decoherence sets in. Based on this analogy with the optical double slit expe...

  5. 气液两相流强化卷式纳滤膜分离硫酸镁水溶液%Enhancement of spiral nanofiltration membranes using gas sparging: application to MgSO4 solution

    柳琦杰; 王枢; 郭竹洁; 谢成胜


    气液两相流强化卷式纳滤膜分离实验是针对DK2540卷式纳滤膜,采用气液两相流强化分离技术,对硫酸镁溶液进行研究,较系统地研究了温度、料液浓度、过膜压力、料液流速、气体流速等因素在分离硫酸镁溶液时,对膜通量、截留率和膜通量增加率的影响,并总结了气液两相流强化效果.结果表明,气液两相流强化卷式纳滤膜分离有明显的效果.温度宜在30~40℃.料液浓度越大、过膜压力越小、气液比越大,气液两相流强化效果越明显.%This study aims at the enhancement in nanofiltration process of aqueous solutions of inorganic salts and provides reference values for industrial application. Gas-sparged nanofiltration experiments with aqueous solution of MgSO4 were performed using a DK2540F element spiral nanofilitration membrane module. The permeate flux and the enhancement from gas sparging were measured in the following operation ranges; temperature 28-36℃,feed concentration 20-50 g o L-1 ,transmembrane pressure 0.4-0.7 MPa,air/liquid ratio 1.0-3.5,and air velocity 1.0-3.5 m o s-1 . The effects of different conditions on the permeate flux,rejection and increment rate of permeate flux of nanofiltration membrane were investigated. The experimental results show that gas sparging can significantly increase the permeate flux and rejection of MgSO4 aqueous solution,appropriate temperature is between 30℃ and 40℃ and feed concentration,transmembrane pressure,and air/liquid have profound effects on the permeate flux and rejection rate of MgSO4 aqueous solution,and the flux enhancement is more significant at higher feed concentration,lower transmembrane pressure,and higher air/liquid.

  6. Effect of ion pairing on the fluorescence of berberine, a natural isoquinoline alkaloid

    Megyesi, Mónika; Biczók, László


    Effect of association with chloride or perchlorate anions on the fluorescence properties of berberine, a cationic isoquinoline alkaloid, has been studied. Interaction with Cl - caused more efficient fluorescence quenching; it significantly accelerated the radiationless deactivation and slowed down the radiative transition. Combined analysis of spectrophotometric, steady-state and time-resolved fluorescence results provided 1.5 × 10 5 M -1 for the equilibrium constant of ion pairing with Cl - in CH 2Cl 2. Both ion pairing and enrichment of the microenvironment of berberine in ions led to excited state quenching in solvents of medium polarity, but only the latter effect was observed in the presence of perchlorates in butyronitrile.

  7. Photodissociation Efficiency Spectroscopy Study of the Rydberg Excited Ion-Pair States of Carbon Dioxide

    Feng, Qiang; Xu, Yun-Feng; Sun, Jin-Da; Tian, Shan-Xi; Shan, Xiao-Bin; Liu, Fu-Yi; Sheng, Liu-Si


    Photodissociation efficiency spectrum of anionic oxygen atom produced via ion-pair dissociations of carbon dioxide is recorded by means of the synchrotron radiation excitation (XUV photon energy 17.40-20.00 eV). The present spectrum is assigned as the Rydberg-like excited ion-pair states, i.e., Tanaka-Ogawa and Henning series, tilde C2Σg+ (CO+2) vibrational ground-state and excitation series. Three Rydberg series, npσu, npπu, and nfu, converging to tilde C2Σg+ (0, 0, 0), show the higher cross sections.

  8. Ion pair formation in copper sulfate aqueous solutions at high temperatures

    Mendez De Leo, Lucila P. [Unidad de Actividad Quimica, Comision Nacional de Energia, Avenida del Libertador 8250, 1429 Ciudad de Buenos Aires (Argentina); Escuela de Ciencia y Tecnologia, Universidad Nacional General San Martin, Alem 3901, 1653 Villa Ballester (Argentina); Bianchi, Hugo L. [Unidad de Actividad Quimica, Comision Nacional de Energia, Avenida del Libertador 8250, 1429 Ciudad de Buenos Aires (Argentina); Escuela de Ciencia y Tecnologia, Universidad Nacional General San Martin, Alem 3901, 1653 Villa Ballester (Argentina); Fernandez-Prini, Roberto [Unidad de Actividad Quimica, Comision Nacional de Energia, Avenida del Libertador 8250, 1429 Ciudad de Buenos Aires (Argentina) and INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, 1428 Ciudad de Buenos Aires (Argentina)]. E-mail:


    Ionic association between Cu{sup 2+}(aq) and SO42-(aq) has been studied in the temperature range (298 to 473) K using a spectrophotometric technique. Experiments were designed to minimize the contribution of other protolytic equilibria in solution. The values of the ionic association equilibrium constant at different temperatures and pressures were fitted to an appropriate equation that allows the calculation of the thermodynamic quantities for states close to the saturation line. Using Bjerrum's model for ionic association evidence for two ion pair populations was obtained. The process of ion pairing is discussed and a possibility to reconcile the continuum model (Bjerrum) with molecular simulation results is suggested.

  9. Ion Transport and All-Solid Battery Characterization Studies on Mg2+-ION Conducting Nano-Composite Polymer Electrolyte (NCPEs):. (75PEO: 25MgSO4) + x MgO

    Agrawal, R. C.; Mahipal, Y. K.; Sahu, Dinesh; Keshrawani, Priyanka


    Characterization of ion transport property on Mg2+-ion conducting Nano Composite Polymer Electrolytes (NCPEs): (75PEO: 25MgSO4) + x MgO, where x = 0, 1, 2, 3, 4, 5, 6, 8, 10, 12 wt. (%) has been reported. Solid Polymer Electrolyte (SPE) composition: [75PEO: 25MgSO4)], identified as the highest conducting film in an earlier study with room temperature conductivity σ ˜ 3.38 × 10-7 S /cm, has been used as Ist-phase host matrix and active filler MgO particles (micro / nano-dimension) as IInd - phase dispersoid. NCPE films have been prepared by a novel hot-press technique in place of the traditional solution cast method. Hot-press technique is recently receiving wider acceptability to cast polymeric electrolyte films due to the fact that it is a completely dry/solvent free/rapid/inexpensive procedure as compared to solution cast method. The Optimum Conducting Composition (OCC) of NCPE film has been identified from the filler-dependent conductivity measurements. As a consequence of dispersal of nano-size particles, the room temperature conductivity (σ) in NCPE OCC film increased by an order of magnitude i.e. σ ˜ 2.29 × 10-6 Scm-1. The quality of the film also improved substantially. The total ionic transference number (tion) and the cationic (Mg2+) transport number (t+) have been determined using dc polarization and a combined ac/dc technique respectively. A considerable increase in t+ could be achieved with the dispersal of nanoparticles. The confirmation of the salt-complexation in PEO polymer was done by FTIR spectroscopic studies. The temperature dependent conductivity measurements were carried out in NCPE OCC film and the activation energy (Ea) has been computed from `log σ - 1/T' Arrhenius plot. All-solid-state battery has been fabricated in the cell configuration: Mg (anode) // NCPE OCC film// MnO2 + C + Electrolyte (cathode), in which both the cathode and anode were in the form of thin pellet. The Open Circuit Voltage (OCV) ˜ 1.82 V was obtained. The cell performance has been studied by recording the cell potential discharge profiles at room temperature under different load conditions.

  10. Observation of pH Value in Electrokinetic Remediation using various electrolyte (MgSO4, KH2PO4 and Na(NO3)) for Barren Acidic Soil at Ayer Hitam, Johor, Malaysia

    Norashira, J.; Zaidi, E.; Aziman, M.; Saiful Azhar, A. T.


    Barren acidic soil collected at Ayer Hitam, Johor Malaysia was recorded at pH value of 2.36 with relative humidity of 86%. This pH value is not suitable for the growth of any plants especially for the soil stabilization purposes. Gradation weathering within the range of 4 to 6 indicates an incomplete/partial weathering process. The soil grade in this range is known as a black shale mudstone. Beside, this also influences to a factor of the high surface water runoff at this particular soil species. As the acidic pH become a major problem for soil fertilizing hence an appropriate technique was implemented known as using ‘Electrokinetic Remediation’, EKR. This technique has a great potential in changing the soil pH value from acidic to less acidic and also kept maintain the pH at the saturated rate of electrochemical process. This research study presents the monitoring data of pH value due to the effect of various electrolyte consist of 0.5M of MgSO4, KH2PO4, and Na(NO3). Here, the distilled water (DW) was used as reference solution. The electric field was provided by dipping two pieces of identical rectangular aluminum foil as anode and cathode. The EKR was conducted under a constant voltage gradient of 50 V/m across the sample bulk at 0.14 m length measured between both electrodes. The data collection was conducted during the total period of 7 days surveillance. The variation of pH values at the remediation area between anode and cathode for various type of electrolyte indicates that there are a significant saturated value as it reaches 7 days of treatment. During the analysis, it is found that the highest pH value at the remediation area after 7 days treatment using Na(NO3), KH2PO4 and MgSO4 was 3.93, 3.33 and 3.39 respectively. Hence from the last stage of pH value observation, it can be conclude that the best electrolyte for barren soil treatment is Na(NO3) whereby it contribute to highest pH value and turn the soil to be less acidic.

  11. Simultaneous quantitative analysis of metabolites using ion-pair liquid chromatography-electrospray ionization mass spectrometry

    Coulier, L.; Bas, R.; Jespersen, S.; Verheij, E.; Werf, M.J. van der; Hankemeier, T.


    We have developed an analytical method, consisting of ion-pair liquid chromatography coupled to electrospray ionization mass spectrometry (IP-LC-ESI-MS), for the simultaneous quantitative analysis of several key classes of polar metabolites, like nucleotides, coenzyme A esters, sugar nucleotides, an

  12. Separation and quantitation of methenamine in urine by ion-pair extraction.

    Strom, J G; Jun, H W


    An ion-pair extraction technique is described for separating methenamine, a urinary tract antibacterial agent, from formaldehyde in human urine samples. Separation conditions are developed from extraction constants for the methenamine-bromocresol green ion-pair. The technique involves adsorption of the ion-pair onto a silica cartridge and elution with methylene chloride:1-pentanol (95:5). Methenamine is freed from the ion-pair by the addition of excess tetrabutylammonium iodide and converted to formaldehyde (determined spectrophotometrically) by reaction with ammonia and acetylacetone. Linear standard plots were obtained from urine containing methenamine which was diluted to 10-160 micrograms/mL. The lower limit of detection was 6 micrograms/mL of methenamine. Absolute recovery from urine was greater than or equal to 94.5%. The precision (CV) of detection of methenamine in the presence of formaldehyde was less than 2%, and less than or equal to 4.5% for the detection of formaldehyde in the presence of methenamine. No interferences were noted. The applicability of the method was demonstrated by analysis of human urine levels of both methenamine and formaldehyde following oral administration of a methenamine salt to a volunteer.

  13. High-speed ion-pair partition chromatography in pharmaceutical analysis.

    Santi, W; Huen, J M; Frei, R W


    Ion-pair chromatography offers attractive possibilities in pharmaceutical analysis. The specificity of the separation systems can be varied over a wide range by appropriate selection of the stationary phase. The choice of a suitable counter-ion can also drastically improve the detection limit, permitting the determination of drug substances in low dosage and possibly of by-products or breakdown products. Ion-pair chromatography of tropane and ergot alkaloids has been investigated using picrate as counter-ion. Alumina, Kieselguhr and various grades of silica gel have been tested as supports. Partition properties studied in a batch procedure have been compared with the actual chromatographic conditions. Columns (10 cm) filled with silical gel (particle size, 5 mum; pore size, 1000 A) show the best performance in the separation of hyoscyamine, scopolamine and ergotamine as picrate ion-pairs. Close control of pH and temperature is essential for reproducible separations. Improvements in detection limits between 100 and 300 times have been observed with these systems. Ion-pair extractions of these alkaloids from dosage forms can be used for sample preparation prior to injection on the the column. This provides an added degree of selectivity and sensitivity.

  14. Preparation and Microbiological Evaluation of Amphiphilic Kanamycin-Lipoamino Acid Ion-Pairs

    Rosario Pignatello


    Full Text Available Amphiphilic ion-pairs of kanamycin (KAN were prepared by evaporation of a water-ethanol co-solution of KAN base and a lipoamino acid bearing a 12-carbon atoms alkyl side chain (LAA12, at different molar ratios. Infrared spectroscopy confirmed the structure of ion-pairs, while differential scanning calorimetry (DSC and powder X-ray diffractometry (PXRD studies supported the formation of new saline species with a different crystalline structure than the starting components. The solubility pattern shown in a range of both aqueous and organic solvents confirmed that the ion-pairs possess an amphiphilic character. The LAA12 counter-ion showed not to improve the antibacterial activity of KAN, suggesting that such chemical strategy is not able to favor the penetration of this drug inside the bacteria cells. Nevertheless, a slight improving, i.e., a one-fold dilution, was observed in E. coli. The present study can also serve as the basis for a further evaluation of LAA ion-pairing of antibiotics, as a means to improve the loading of hydrophilic drugs into lipid-based nanocarriers.

  15. Comprehensive Analysis of Umami Compounds by Ion-Pair Liquid Chromatography Coupled to Mass Spectrometry

    Coulier, L.; Bas, R.; Hekman, M.; Werff, B.J.C. van der; Burgering, M.; Thissen, U.


    An ion-pair LC-ESI-MS method was developed capable of analyzing various reported umami or umami-enhancing compounds, including glutamic acid and 5'-ribonucleotides. The method was validated using tomato and potato samples and showed overall good analytical performance with respect to selectivity, de

  16. Ion pair formation and primary charging behavior of titanium oxide (anastase and rutile)

    Bourikas, K.; Hiemstra, T.; Riemsdijk, van W.H.


    The primary charging behavior of titanium oxide (anatase, rutile, and P25) and the ion pair formation of the electrolyte ions with the surface groups have been extensively studied. A large number of titration and electrokinetic data sets available in the literature have been successfully described,

  17. Use of chlorine kinetic isotope effects for evaluating ion pairing in nucleophilic displacements at saturated carbon

    Graczyk, D.G.; Taylor, J.W.; Turnquist, C.R.


    Use of the Winstein scheme to describe ion pairing leads to the conclusion that chlorine kinetic isotope effects (KIE) are primarily responsive to processes involving the covalently bound chlorine and less indicative of reactions which occur after the formation of the initial ion pair. This conclusion has been tested by showing that the calculated equilibrium isotope effect (1.0057) and observed (1.0059/sub 6/ +- 0.0001/sub 1/) KIE are nearly identical when the solvolysis of p-methylbenzyl chloride is forced toward a limiting case with 97% trifluoroethanol as solvent. The reaction of p-phenoxybenzyl chloride showed similar behavior with an equilibrium KIE value of 1.0058/sub 4/ +- 0.0001/sub 1/. These results suggest that competing ion-pair and S/sub N/2 processes may be one factor contributing to Hammett plot curvature for these nucleophilic displacement reactions. Chloride KIE values for the reaction of n-butyl chloride with thiophenoxide anion, where ion pairing does not occur, show little variation with a wide variety of solvents. 3 tables.

  18. Excited-state proton transfer and ion pair formation in a Cinchona organocatalyst

    Kumpulainen, T.; Brouwer, A.M.


    The excited-state proton transfer and subsequent intramolecular ion pair formation of a cupreidine-derived Cinchona organocatalyst (BnCPD) were studied in THF-water mixtures using picosecond time-resolved fluorescence together with global analysis. Full spectral and kinetic characterization of all t

  19. Ion-pairing reversed-phased chromatography/mass spectrometry of heparin

    Henriksen, Jens; Roepstorff, Peter; Ringborg, Lene Hoffmeyer


    not well characterised. In order to further characterise such mixtures, two on-line ion-pairing reverse-phased chromatography electrospray ionisation (ESI) mass spectrometry methods have been developed. One of the systems allows the determination of more than 200 components in a medium molecular weight...

  20. Distribution of 1-alkyl-3-methylimidazolium ions and their ion pairs between dichloromethane and water.

    Katsuta, Shoichi; Yamaguchi, Naoko; Ogawa, Ryuji; Kudo, Yoshihiro; Takeda, Yasuyuki


    The distribution behavior of the salts of a series of 1-alkyl-3-methylimidazolium cations (RMeIm(+); R = butyl, hexyl, and octyl) with tetrafluoroborate (BF(4)(-)), hexafluorophosphate (PF(6)(-)), bis(trifluoromethanesulfonyl)amide (NTf(2)(-)), and 2,4,6-trinitrophenolate (Pic(-)) anions has been investigated in a dichloromethane-water system at 25 degrees C. The distribution constants (K(D)) of the ion pairs and the transfer activity coefficients ((o)gamma(w)) of the single ions were determined. For the ion pairs with a given anion, the log K(D) value increases linearly with the number of methylene groups (N(CH2)) in the cation, which can be explained by using the regular solution theory. A similar relationship was observed between log (o)gamma(w) and N(CH2) for the free RMeIm(+) ions, and the result was discussed by decomposing the transfer activity coefficient into the Born-type electrostatic contribution and the non-electrostatic one. For the free anions and their ion pairs with a given cation, the (o)gamma(w) and K(D) values increase with increasing molar volume of the anion: i.e., BF(4)(-) ion-pair formation in water are also discussed by comparing the present results with those of tetraalkylammonium salts previously reported.

  1. Computational studies of ion pairing. 8. Ion pairing of tetraalkylammonium ions to nitrosobenzene and benzaldehyde redox species. A general binding motif for the interaction of tetraalkylammonium ions with benzenoid species.

    Fry, Albert J


    Very little data is available on the detailed structures of ion pairs in solution, since few general experimental methods are available for obtaining such information. For this reason, computational methods have emerged as the method of choice for determining the structures of organic ion pairs in solution. The present study examines the ion pairs between a series of tetraalkylammonium ions and several redox forms of nitrosobenzene and a series of substituted benzaldehydes. The structures, though previously unexpected, are chemically reasonable and fit into a previous pattern of ion pairing described in previous publications in this series. To date in these studies, a total of 73 ion pairs and related species have in fact been identified having exactly the same unusual orientation of the tetraalkylammonium component with respect to the donor species. The results are pertinent to topics of general current interest, including self-assembly, molecular recognition, and supramolecular assembly.

  2. Spectrofluorimetric determination of doxepin hydrochloride in commercial dosage forms via ion pair complexation with alizarin red S

    Rahman, Nafisur; Khatoon, Asma


    .... It is based on the formation of ion-pair complex between doxepin and alizarin red S at pH 3.09. The ion pair complex was extracted in dichloromethane and the fluorescence intensity was measured at 560 nm after excitation at 490 nm...

  3. Simultaneous Determination of Chelating Agents by Ion-Suppression and Ion-Pair Chromatography in Wastewater

    Dodi, Alain; Bouscarel, Maelle [Commissariat a l' energie atomique - C.E.A, Centre d' Etude de Cadarache, Laboratoire d' Analyses Radiochimiques et Chimiques, St Paul lez Durance (France)


    This article describes two methods for analysing chelating agents found in nuclear waste. First, ion-suppression chromatography using an anion exchange stationary phase and mobile phase consisting of a nitric acid solution and pure water gradient. UV detection was performed at 330 nm after the reaction with a post-column reagent composed of iron nitrate in perchloric acid. Secondly, ion-pair chromatography with a mobile phase consisting of a mixture of nitric acid, tetra-butyl-ammonium hydrogeno-sulphate, tetra-butyl-ammonium hydroxide and iron chloride. A reversed-phase material was used as a stationary phase and detection was performed by direct measurement of the UV absorption at 260 nm. The quantification limits were lower for ion-pair chromatography than for ion-suppression chromatography. Both methods were easy to implement and allow a multi-element separation in less than 30 min with low detection limits. (authors)

  4. Quantum Zeno Effect Underpinning the Radical-Ion-Pair Mechanism of Avian Magnetoreception

    Kominis, I K


    The intricate biochemical processes underlying avian magnetoreception, the sensory ability of migratory birds to navigate using earths magnetic field, have been narrowed down to spin-dependent recombination of radical-ion pairs to be found in avian species retinal proteins. The avian magnetic field detection is governed by the interplay between magnetic interactions of the radicals unpaired electrons and the radicals recombination dynamics. Critical to this mechanism is the long lifetime of the radical-pair spin coherence, so that the weak geomagnetic field will have a chance to signal its presence. It is here shown that a fundamental quantum phenomenon, the quantum Zeno effect, is at the basis of the radical-ion-pair magnetoreception mechanism. The quantum Zeno effect naturally leads to long spin coherence lifetimes, without any constraints on the systems physical parameters, ensuring the robustness of this sensory mechanism. Basic experimental observations regarding avian magnetic sensitivity are seamlessly...

  5. Quantum Zeno Effect Underpinning the Radical-Ion-Pair Mechanism of Avian Magnetoreception

    Kominis, I. K.


    The intricate biochemical processes underlying avian magnetoreception, the sensory ability of migratory birds to navigate using earths magnetic field, have been narrowed down to spin-dependent recombination of radical-ion pairs to be found in avian species retinal proteins. The avian magnetic field detection is governed by the interplay between magnetic interactions of the radicals unpaired electrons and the radicals recombination dynamics. Critical to this mechanism is the long lifetime of t...

  6. Ion pairing and phase behaviour of an asymmetric restricted primitive model of ionic liquids

    Lu, Hongduo; Li, Bin; Nordholm, Sture; Woodward, Clifford E.; Forsman, Jan


    An asymmetric restricted primitive model (ARPM) of electrolytes is proposed as a simple three parameter (charge q, diameter d, and charge displacement b) model of ionic liquids and solutions. Charge displacement allows electrostatic and steric interactions to operate between different centres, so that orientational correlations arise in ion-ion interactions. In this way the ionic system may have partly the character of a simple ionic fluid/solid and of a polar fluid formed from ion pairs. The present exploration of the system focuses on the ion pair formation mechanism, the relative concentration of paired and free ions and the consequences for the cohesive energy, and the tendency to form fluid or solid phase. In contrast to studies of similar (though not identical) models in the past, we focus on behaviours at room temperature. By MC and MD simulations of such systems composed of monovalent ions of hard-sphere (or essentially hard-sphere) diameter equal to 5 Å and a charge displacement ranging from 0 to 2 Å from the hard-sphere origin, we find that ion pairing dominates for b larger than 1 Å. When b exceeds about 1.5 Å, the system is essentially a liquid of dipolar ion pairs with a small presence of free ions. We also investigate dielectric behaviours of corresponding liquids, composed of purely dipolar species. Many basic features of ionic liquids appear to be remarkably consistent with those of our ARPM at ambient conditions, when b is around 1 Å. However, the rate of self-diffusion and, to a lesser extent, conductivity is overestimated, presumably due to the simple spherical shape of our ions in the ARPM. The relative simplicity of our ARPM in relation to the rich variety of new mechanisms and properties it introduces, and to the numerical simplicity of its exploration by theory or simulation, makes it an essential step on the way towards representation of the full complexity of ionic liquids.

  7. Two state electron model for geminate recombination of electron-ion pairs in liquid isooctane

    Lukin, L. V.; Yakovlev, B. S.


    Recombination kinetics of geminate electron-ion pairs is considered in the framework of the two state model for electron transport in liquid hydrocarbons. It is shown that the model well reproduces recent experimental data on the subpicosecond geminate recombination obtained in liquid isooctane. The life time of electrons in a localized state in isooctane is estimated to lie in the range between 0.14 ps and 0.57 ps at room temperature.

  8. Extractive Spectrophotometric Determination of Fluconazole by Ion-pair Complex Formation with Bromocresol Green

    JALALI,Fahimeh; RAJABI,Mohammad J.


    An extraction-spectrophotometric method for the determination of trace amounts of fluconazole was described.Fluconazole was effectively extracted as a 1 : 1 ion-pair complex with bromocresole green (BCG) at pH 3.0 into chloroform, followed by spectrophotometric determination at 420 nm. Beer's law was obeyed over the range of 4-procedure was applied to the determination of fluconazole in pharmaceutical preparations as well as its recovery from a blood serum sample.

  9. Novel additives for the separation of organic acids by ion-pair chromatography


    This paper proposes the use of novel surfactant additives for the separation of organic acids by ion-pair chromatography and studies the influences of surfactants on the chromatographic separation behaviors.Researches have been carried out on both silica gel matrix and polymer supporters in order to compare the two ordinary kinds of stationary phases,and the phenomenon is similar. Separation is based on differences in the stabilities of analyte-additive complexes in solution.Retention times of analytes c...

  10. Ion pair formation in water. association constants of bolaform, bisquaternary ammonium, electrolytes by chemical trapping.

    Geng, Yan; Romsted, Laurence S


    The first and second association constants, K1 and K2, for ion pair formation in aqueous 0.02-3.5 M solutions of bis(trimethyl)-alpha,omega-alkanediammonium halides with variable spacer lengths, 1-n-1 2X (n = 2-4, X = Cl, Br) and bolaform salts and for tetramethylammonium halides (TMAX, X = Cl, Br), K(TMAX), were determined by the chemical trapping method. Values for K(TMAX) are small, K(TMABr) = 0.83 M(-1) and K(TMACl) = 0.29 M(-1), in agreement with literature values. For the bolaform salts, K1 depends on spacer length and counterion type, ranges from 0.4 to 17 M(-1), is 2-10 times larger than K2, is larger for Br- than Cl-, and decreases by a factor of approximately 3 for Cl- and approximately 10 for Br- as n increases from 2 to 4. K2, for the formation of bolaform dihalide pair, is essentially the same as that for ion pair formation in TMAX solutions, i.e., K2 approximately K(TMAX). Values of K1 and K(TMABr) obtained from changes in 79Br line widths are in good agreement with those obtained by chemical trapping. The results are consistent with a thermodynamic model in which the ion association depends on the balance of the ion specific hydration free energies of cations and anions and their ion specific and hydration interactions in ion pairs. Spacer length dependent ion pairing by bolaform electrolytes, which are analogues of the headgroups and counterions of gemini amphiphiles, suggests a new model for the spacer length dependent sphere-to-rod transitions of gemini micelles. Neutral, but polar, headgroup-counterion pairs have a lower demand for hydration that free headgroups and counterions, and headgroup-counterion pair formation releases interfacial water into the bulk aqueous phase, permitting tighter amphiphile packing in rodlike micelles.

  11. Comprehensive mechanistic study of ion pair SN2 reactions of lithium isocyanate and methyl halides

    Sun, Ying-Xin; Ren, Yi; Wong, Ning-Bew; Chu, San-Yan; Xue, Ying

    The anionic SN2 reactions NCO- + CH3X and ion pair SN2 reactions LiNCO + CH3X (X = F, Cl, Br, and I) at saturated carbon with inversion and retention mechanisms were investigated at the level of MP2/6-311+G(d,p). There are two possible reaction pathways in the anionic SN2 reactions, but eight in the ion pair SN2 reactions. Calculated results suggest that the previously reported T-shaped isomer of lithium isocyanate does not exist. All the retention pathways are not favorable based on the analysis of transition structures. Two possible competitive reaction pathways proceed via two six-member ring inversion transition structures. It is found that there are two steps in the most favorable pathway, in which less stable lithium cyanate should be formed through the isomerization of lithium isocyanate and nucleophilic site (N) subsequently attacks methyl halides from the backside. The thermodynamically and kinetically favorable methyl isocyanate is predicted as major product both in the gas phase anionic and the ion pair SN2 reactions. In addition, good correlations between the overall barriers relative to separated reactants, ?H?ovr , with geometrical looseness parameter %L? and the heterolytic cleavage energies of the C bond X and Li bond N (or Li bond O) bonds are observed for the anionic and ion pair SN2 reactions. The trend of variation of the overall barriers predicts the leaving ability of X increase in the order: F reactions of LiNCO + CH3X. The calculations in solution indicate that solvent effects will retard the rate of reactions and the predicted product, methyl isocyanate, is same as the one in the gas phase.

  12. Luminescent ion pairs with tunable emission colors for light-emitting devices and electrochromic switches.

    Guo, Song; Huang, Tianci; Liu, Shujuan; Zhang, Kenneth Yin; Yang, Huiran; Han, Jianmei; Zhao, Qiang; Huang, Wei


    Most recently, stimuli-responsive luminescent materials have attracted increasing interest because they can exhibit tunable emissive properties which are sensitive to external physical stimuli, such as light, temperature, force, and electric field. Among these stimuli, electric field is an important external stimulus. However, examples of electrochromic luminescent materials that exhibit emission color change induced by an electric field are limited. Herein, we have proposed a new strategy to develop electrochromic luminescent materials based on luminescent ion pairs. Six tunable emissive ion pairs (IP1-IP6) based on iridium(iii) complexes have been designed and synthesized. The emission spectra of ion pairs (IPs) show concentration dependence and the energy transfer process is very efficient between positive and negative ions. Interestingly, IP6 displayed white emission at a certain concentration in solution or solid state. Thus, in this contribution, UV-chip (365 nm) excited light-emitting diodes showing orange, light yellow and white emission colors were successfully fabricated. Furthermore, IPs displayed tunable and reversible electrochromic luminescence. For example, upon applying a voltage of 3 V onto the electrodes, the emission color of the solution of IP1 near the anode or cathode changed from yellow to red or green, respectively. Color tunable electrochromic luminescence has also been realized by using other IPs. Finally, a solid-film electrochromic switch device with a sandwiched structure using IP1 has been fabricated successfully, which exhibited fast and reversible emission color change.

  13. Dependence of the rate of LiF ion pairing on the description of molecular interaction

    Pluharova, Eva; Baer, Marcel D.; Schenter, Gregory K.; Jungwirth, Pavel; Mundy, Christopher J.


    We present an analysis of the dynamics of ion-pairing of Lithium Fluoride (LiF) in aqueous solvent using both detailed molecular simulation as well as reduced models within a Gener- alized Langevin Equation (GLE) framework. We explored the sensitivity of the ion-pairing phenomena to the details of descriptions of molecular interaction, comparing two empirical potentials to explicit quantum based density functional theory. We find quantitative differences in the potentials of mean force for ion-pairing as well as time dependent frictions that lead to variations in the rate constant and reactive flux correlation functions. These details reflect differences in solvent response to ion-pairing between different representations of molecular interaction and influence anharmonicity of the dynamic response. We find that the short time anharmonic response is recovered with a GLE parameterization. Recovery of the details of long time response may require extensions to the reduced model. We show that the utility of using a reduced model leads to a straight forward application of variational transition state the- ory concepts to the condensed phase system. The significance of this is reflected in the analysis of committor distributions and the variation of planar hypersurfaces, leading to an improved understanding of factors that determine the rate of LiF ion-pairing. CJM and GKS are supported by the U.S. Department of Energy‘s (DOE) Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest Na- tional Laboratory (PNNL) is operated for the Department of Energy by Battelle. MDB is grateful for the support of Laboratory Directed Research and Development funding under the auspices of PNNL’s Laboratory Initiative Materials Synthesis and Simulation across Scales (MS3). Additional computing resources were generously allocated by PNNL’s Institutional Computing program. EP acknowledges support from PNNL’s Alternate Sponsored

  14. Reversed-phase ion-pair high-performance liquid chromatography assay of polyprenyl diphosphate oligomer homologues.

    Kozlov, Vyacheslav V; Danilov, Leonid L


    A reversed-phase ion-pair high-performance liquid chromatography procedure was developed for the separation of polyprenyl diphosphate oligomer homologues obtained chemically from plant polyprenols. Tetrabutylammonium phosphate was used as the ion-pair reagent, and the dependence of the separation quality on pH of ion-pair reagent was investigated for the first time. The procedure is applicable for the control of commercial available polyprenyl monophosphates (the active components of veterinary drugs Phosprenyl and Gamapren) for the possible presence of polyprenyl diphosphate byproducts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Hydration and ion pair formation in common aqueous La(III) salt solutions--a Raman scattering and DFT study.

    Rudolph, Wolfram W; Irmer, Gert


    Raman spectra of aqueous lanthanum perchlorate, triflate (trifluorosulfonate), chloride and nitrate solutions were measured over a broad concentration (0.121-3.050 mol L(-1)) range at room temperature (23 °C). A very weak mode at 343 cm(-1) with a full width at half height at 49 cm(-1) in the isotropic spectrum suggests that the nona-aqua La(III) ion is thermodynamically stable in dilute perchlorate solutions (∼0.2 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The La(3+) nona-hydrate was also detected in a 1.2 mol L(-1) La(CF3SO3)3(aq). In lanthanum chloride solutions chloro-complex formation was detected over the measured concentration range from 0.5-3.050 mol L(-1). The chloro-complexes in LaCl3(aq) are fairly weak and disappear with dilution. At a concentration complexes disappeared. In LaCl3 solutions, with additional HCl, a series of chloro-complexes of the type [La(OH2)(9-n)Cln](+3-n) (n = 1-3) were formed. The La(NO3)3(aq) spectra were compared with a spectrum of a 0.409 mol L(-1) NaNO3(aq) and it was concluded that in La(NO3)3(aq) over the concentration range from 0.121-1.844 mol L(-1), nitrato-complexes, [La(OH2)(9-n)(NO3)n](+3-n) (n = 1, 2) were formed. These nitrato-complexes are quite weak and disappear with dilution La(OH2)9](3+) with the polarizable dielectric continuum are in good agreement with data from recent structural experimental measurements and high quality simulations. The DFT frequency of the La-O stretching mode at 328.2 cm(-1), is only slightly smaller than the experimental one.

  16. Separation of seven arsenic species by ion-pair and ion-exchange high performance liquid chromatography

    Larsen, Erik Huusfeldt; Hansen, Sven Hedegaard


    Arsenite, arsenate, monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine and the tetramethylarsonium ion were subjected to ion-exchange and ion-pair reversed phase HPLC. The ion exchange method was superior in selectivity and time of analysis for the arsenic anions. The ammonium ions...... used for the ion-pair method only resulted in separation of some of the anionic arsenic compounds. Flame atomic absorption spectrometry was used for on-line arsenic-specific detection....

  17. Quantum Theory of Radical-Ion-Pair Recombination: A New Physical Paradigm for Low-Magnetic-Field Effects

    Kominis, I. K.


    A new paradigm emerging in the description of magnetic-sensitive radical-ion-pair recombination reactions is presented. This paradigm is founded on the realization that the recombination process of radical-ion pairs is a continuous quantum measurement. In the regime of low magnetic fields we describe the appearance of purely quantum phenomena, that fade away as the magnetic field increases. We will analyze the magnetic sensitivity of these reactions under this perspective and bridge the new f...

  18. Intensified extraction of ionized natural products by ion pair centrifugal partition extraction.

    Hamzaoui, Mahmoud; Hubert, Jane; Hadj-Salem, Jamila; Richard, Bernard; Harakat, Dominique; Marchal, Luc; Foucault, Alain; Lavaud, Catherine; Renault, Jean-Hugues


    The potential of centrifugal partition extraction (CPE) combined with the ion-pair (IP) extraction mode to simultaneously extract and purify natural ionized saponins from licorice is presented in this work. The design of the instrument, a new laboratory-scale Fast Centrifugal Partition Extractor (FCPE300(®)), has evolved from centrifugal partition chromatography (CPC) columns, but with less cells of larger volume. Some hydrodynamic characteristics of the FCPE300(®) were highlighted by investigating the retention of the stationary phase under different flow rate conditions and for different biphasic solvent systems. A method based on the ion-pair extraction mode was developed to extract glycyrrhizin (GL), a biologically active ionic saponin naturally present in licorice (Glycyrrhiza glabra L., Fabaceae) roots. The extraction of GL was performed at a flow rate of 20 mL/min in the descending mode by using the biphasic solvent system ethyl acetate/n-butanol/water in the proportions 3/2/5 (v/v/v). Trioctylmethylammonium with chloride as a counter-ion (Al336(®)) was used as the anion extractant in the organic stationary phase and iodide, with potassium as counter-ion, was used as the displacer in the aqueous mobile phase. From 20 g of a crude extract of licorice roots, 2.2g of GL were recovered after 70 min, for a total process duration of 90 min. The combination of the centrifugal partition extractor with the ion-pair extraction mode (IP-CPE) offers promising perspectives for industrial applications in the field of natural product isolation or for the fractionation of natural complex mixtures.

  19. Simulation Based on Negative ion pair Techniques of Electric propulsion In Satellite Mission Using Chlorine Gas

    Bakkiyaraj, R.

    R.Bakkiyaraj,Assistant professor,Government college of Engineering ,Bargur,Tamilnadu. *C.Sathiyavel, PG Student and Department of Aeronautical Engineering/Branch of Avionics, PSN college of Engineering and Technology,Tirunelveli,India. Abstract: Ion propulsion rocket system is expected to become popular with the development of ion-ion pair techniques because of their stimulated of low propellant, Design of repulsive between negative ions with low electric power and high efficiency. A Negative ion pair of ion propulsion rocket system is proposed in this work .Negative Ion Based Rocket system consists of three parts 1.ionization chamber 2. Repulsion force and ion accelerator 3. Exhaust of Nozzle. The Negative ions from electro negatively gas are produced by attachment of the gas ,such as chlorine with electron emitted from a Electron gun ionization chamber. The formulate of large stable negative ion is achievable in chlorine gas with respect to electron affinity (∆E). When a neutral chlorine atom in the gaseous form picks up an electron to form a cl- ion, it releases energy of 349 kJ/mol or 3.6 eV/atom. It is said to have an electron affinity of -349 kJ/mol ,the negative sign indicating that energy is released during this process .The distance between negative ions pair is important for the evaluation of the rocket thrust and is also determined by the exhaust velocity of the propellant. The mass flow rate of ions is related to the ion beam current. Accelerate the Negative ions to a high velocity in the thrust vector direction with a significantly intense grids and the exhaust of negative ions through Nozzle. The simulation of the ion propulsion system has been carried out by MATLAB. By comparing the simulation results with the theoretical and previous results, we have found that the proposed method is achieved of thrust value with low electric power for simulating the ion propulsion rocket system

  20. Lamb Shift in Radical-Ion Pairs is Physically Equivalent to a Spin-Exchange Interaction

    Vitalis, K M


    Radical-ion pairs, fundamental for understanding photosynthesis and the avian magnetic compass, were recently shown to be biological open quantum systems. We here show that the coupling of the radical-pair's spin degrees of freedom to its decohering vibrational reservoir leads to a shift of the radical-pair's magnetic energy levels. The Lamb shift Hamiltonian is diagonal in the singlet-triplet basis, and results in a singlet-triplet energy splitting physically indistinguishable from an exchange interaction. This could have profound implications for understanding photosynthetic reaction centers.

  1. Primary amine/CSA ion pair: A powerful catalytic system for the asymmetric enamine catalysis

    Liu, Chen


    A novel ion pair catalyst containing a chiral counteranion can be readily derived by simply mixing cinchona alkaloid-derived diamine with chiral camphorsulfonic acid (CSA). A mixture of 9-amino(9-deoxy)epi-quinine 8 and (-)-CSA was found to be the best catalyst with matching chirality, enabling the direct amination of α-branched aldehydes to proceed in quantitative yields and with nearly perfect enantioselectivities. A 0.5 mol % catalyst loading was sufficient to catalyze the reaction, and a gram scale enantioselective synthesis of biologically important α-methyl phenylglycine has been successfully demonstrated. © 2011 American Chemical Society.

  2. Ion Pair in Extreme Aqueous Environments, Molecular-Based and Electric Conductance Approaches

    Chialvo, Ariel A [ORNL; Gruszkiewicz, Miroslaw {Mirek} S [ORNL; Simonson, J Michael {Mike} [ORNL; Palmer, Donald [ORNL; Cole, David R [ORNL


    We determine by molecular-based simulation the density profiles of the Na+!Cl! ion-pair association constant in steam environments along three supercritical isotherms to interrogate the behavior of ion speciation in dilute aqueous solutions at extreme conditions. Moreover, we describe a new ultra-sensitive flow-through electric conductance apparatus designed to bridge the gap between the currently lowest steam-density conditions at which we are experimentally able to attain electric conductance measurements and the theoretically-reachable zero-density limit. Finally, we highlight important modeling challenges encountered near the zero-density limit and discuss ways to overcome them.

  3. Flow-injection sample preconcentration for ion-pair chromatography of trace metals in waters.

    Pobozy, Ewa; Halko, Radoslav; Krasowski, Marcin; Wierzbicki, Tomasz; Trojanowicz, Marek


    Selected trace transition metal ions have been determined in an FIA/HPLC hyphenated system using on-line preconcentration on cellulose functionalised sorbent Cellex P. For HPLC separation ion-pair chromatography was employed with spectrophotometric detection at 510 nm using post-column derivatisation with PAR. Favourable kinetic conditions of sorption and elution as well as optimisation of hyphenated system allowed to obtain detection limits at sub-microgL(-1) level at 25 min preconcentration time. The developed method was employed for determination of Co(II), Ni(II), Cd(II) and Mn(II) in river water with reasonable agreement of obtained results with electrothermal AAS determination.

  4. Reverse phase ion pair high pressure liquid chromatographic determination of ethylenediaminetetraacetic acid in crabmeat and mayonnaise.

    Perfetti, G A; Warner, C R


    A method is described for the determination of ethylenediaminetetraacetic acid (EDTA) in crabmeat and mayonnaise. EDTA is extracted from the food sample with water and converted to its copper chelate, which is then quantitated by reverse phase ion pair high pressure liquid chromatography with ultraviolet detection. Maximum sensitivity is obtained with detection at about 254 nm; higher wavelengths may be used for enhanced specificity. Cleanup procedures for crabmeat and mayonnaise were improved by using a radiotracer method. Analyses of crabmeat and mayonnaise samples spiked at 3 different levels showed greater than 90% recovery of EDTA.

  5. Time fractional effect on ion acoustic shock waves in ion-pair plasma

    Abdelwahed, H. G., E-mail: [Prince Sattam Bin Abdulaziz University, College of Science and Humanitarian Studies, Physics Department (Saudi Arabia); El-Shewy, E. K.; Mahmoud, A. A. [Faculty of Science, Mansoura University, Theoretical Physics Group, Physics Department (Egypt)


    The nonlinear properties of ion acoustic shock waves are studied. The Burgers equation is derived and converted into the time fractional Burgers equation by Agrawal’s method. Using the Adomian decomposition method, shock wave solutions of the time fractional Burgers equation are constructed. The effect of the time fractional parameter on the shock wave properties in ion-pair plasma is investigated. The results obtained may be important in investigating the broadband electrostatic shock noise in D- and F-regions of Earth’s ionosphere.

  6. Salt bridges destabilize a leucine zipper designed for maximized ion pairing between helices.

    Phelan, Paul; Gorfe, Alemayehu A; Jelesarov, Ilian; Marti, Daniel N; Warwicker, James; Bosshard, Hans Rudolf


    Interhelical salt bridges are common in leucine zippers and are thought to stabilize the coiled coil conformation. Here we present a detailed thermodynamic investigation of the designed, disulfide-linked leucine zipper AB(SS) whose high-resolution NMR structure shows six interhelical ion pairs between heptad positions g of one helix and e' of the other helix but no ion pairing within single helices. The average pK(a) value of the Glu side chain carboxyl groups of AB(SS) is slightly higher than the pK(a) of a freely accessible Glu in an unfolded peptide [Marti, D. N., Jelesarov, I., and Bosshard, H. R. (2000) Biochemistry 39, 12804-12818]. This indicates that the salt bridges are destabilizing, a prediction we now have confirmed by determining the pH +/- stability profile of AB(SS). Circular dichroism-monitored unfolding by urea and by heating and differential scanning calorimetry show that the coiled coil conformation is approximately 5 kJ/mol more stable when salt bridges are broken by protonation of the carboxyl side chains. Using guanidinium chloride as the denaturant, the increase in the free energy of unfolding on protonation of the carboxyl side chains is larger, approximately 17 kJ/mol. The discrepancy between urea and guanidinium chloride unfolding can be ascribed to the ionic nature of guanidinium chloride, which screens charge-charge interactions. This work demonstrates the difficulty of predicting the energetic contribution of salt bridges from structural data alone even in a case where the ion pairs are seen in high-resolution NMR structures. The reason is that the contribution to stability results from a fine balance between energetically favorable Coulombic attractions and unfavorable desolvation of charges and conformational constraints of the residues involved in ion pairing. The apparent discrepancy between the results presented here and mutational studies indicating stabilization by salt bridges is discussed and resolved. An explanation is

  7. Spectrophotometric Determination of Gemifloxacin Mesylate in Pharmaceutical Formulations Through Ion-Pair Complex Formation

    Marothu Vamsi Krishna


    Full Text Available Four simple and sensitive ion-pairing spectrophotometric methods have been described for the assay of gemifloxacin mesylate (GFX either in pure form or in pharmaceutical formulations. The developed methods involve formation of colored chloroform extractable ion-pair complexes of the drug with safranin O (SFN O and methylene blue (MB in basic medium; Napthol blue 12BR (NB 12BR and azocaramine G (AG in acidic medium. The extracted complexes showed absorbance maxima at 525, 650, 620 and 540 nm for SFN O, MB, NB 12BR and AG, respectively.Beer's law is obeyed in the concentration ranges 3-15, 4-20, 2-10 and 2-10 μg/mL with molar absorptivity of 2.81 × 104, 2.20 x 104, 4.02 × 104 and 4.15 × 104 L mole−1 cm−1 and relative standard deviation of 0.077, 0.104, 0.080 and 0.103% for SFN O, MB, NB 12BR and AG, respectively. These methods have been successfully applied for the assay of drug in pharmaceutical formulations. No interference was observed from common pharmaceutical adjuvants. Results of analysis were validated statistically and through recovery studies.

  8. Highly sensitive ion pair liquid chromatographic determination of albendazole marker residue in animal tissues.

    Fletouris, Dimitrios J; Papapanagiotou, Elias P; Nakos, Dimitrios S; Psomas, Ioannis E


    A simple, rapid, and highly sensitive ion pair liquid chromatographic method for the determination of albendazole sulfoxide, albendazole 2-aminosulfone, and albendazole sulfone, which constitute the marker residue of albendazole in animal tissues (muscle, fat, liver, and kidney), is described. Tissue samples were extracted with acetonitrile, and the extracts were partitioned, as ion pairs, into dichloromethane. The organic layer was evaporated to dryness, and the residue was reconstituted in phosphate buffer and extracted with ethyl acetate. Separation was carried out isocratically with a mobile phase containing both positively and negatively charged pairing ions. Detection was performed fluorometrically, with excitation and emission wavelengths set at 290 and 320 nm, respectively. Overall recoveries were better than 76%, and the overall relative standard deviation was better than 7.3% in all tissues examined. The limits of quantification were 20, 1, and 0.5 ng/g for sulfoxide, 2-aminosulfone, and sulfone metabolites, respectively. The method was successfully applied to determine residues in tissues of two sheep orally administered an albendazole formulation.

  9. Application of partially fluorinated carboxylic acids as ion-pairing reagents in LC/ESI-MS.

    Yamamoto, Eiichi; Ishihama, Yasushi; Asakawa, Naoki


    This report describes the application of partially fluorinated carboxylic acids as ion-pairing reagents for basic analytes in high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (LC/ESI-MS) in positive-ion mode. Partially fluoridated carboxylic acids such as difluoroacetic acid, 3,3,3-trifluoropropionic acid and 3,3,3-trifluoromethyl-2-trifluoromethylpropionic acid functioned as volatile paired-ion similarly as trifluoroacetic acid (TFA). These acids provided basic analytes larger retention factor (k) compared to acetic acid or formic acid in LC. The ESI-MS signal strength of analytes with these acids were higher than that of TFA and was analogous to that of acetic acid or formic acid. The performances of partially fluorinated carboxylic acids in LC and ESI-MS for basic analytes were analyzed by multivariate statistical analysis using physicochemical descriptors of acids. Equations obtained in the analysis enabled us the quantitative evaluation of the performance of fluorinated carboxylic acids as ion-pair reagents for basic analytes in LC/ESI-MS.

  10. Lithium perchlorate ion pairing in a model of amorphous polyethylene oxide

    Halley, J.W.; Duan, Y. [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Curtiss, L.A.; Baboul, A.G. [Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)


    We report a molecular dynamics study of pairing and dynamics of lithium cation and perchlorate anion in a previously reported model of amorphous polyethylene oxide. We are particularly interested in the question of whether these ions pair in the model, as previously reported experimentally. We calculate the potential of mean force between a lithium and perchlorate ion in the system for several temperatures when a pair of ions is at various separation distances in our model. We find evidence for two minima in the potential of mean force, one at lithium{endash}chlorine separations of 3.5 {Angstrom} and about 6.5 {Angstrom}. We studied the same system with five ion pairs in the system and again find two minima at the same separation distances but in this case there is evidence of entropic effects in the binding free energy of the pairs at 3.5 {Angstrom}. A study of radial distribution functions permits us to deduce information concerning the structure of the paired states. {copyright} {ital 1999 American Institute of Physics.}

  11. Ionic force field optimization based on single-ion and ion-pair solvation properties

    Fyta, Maria; Dzubiella, Joachim; Vrbka, Lubos; Netz, Roland R


    Molecular dynamics simulations of ionic solutions depend sensitively on the force fields employed for the ions. To resolve the fine differences between ions of the same valence and roughly similar size and in particular to correctly describe ion-specific effects, it is clear that accurate force fields are necessary. In the past, optimization strategies for ionic force fields either considered single-ion properties (such as the solvation free energy at infinite dilution or the ion-water structure) or ion-pair properties (in the form of ion-ion distribution functions). In this paper we investigate strategies to optimize ionic force fields based on single-ion and ion-pair properties simultaneously. To that end, we simulate five different salt solutions, namely CsCl, KCl, NaI, KF, and CsI, at finite ion concentration. The force fields of these ions are systematically varied under the constraint that the single-ion solvation free energy matches the experimental value, which reduces the two-dimensional $\\{\\sigma,\\e...

  12. Ion pair formation and its effect in PEO:Mg solid polymer electrolyte system

    Jaipal Reddy, M.; Chu, Peter P.

    In poly(ethylene oxide) (PEO) based solid polymer electrolytes, the interaction between cations and the ether oxygen plays a major role in ion conductivity. Measurements with differential scanning calorimetry (DSC) illustrated clearly the modification of the PEO crystalline structure with increasing content of magnesium salt. FTIR spectral studies suggest interaction of Mg 2+ cations with the ether oxygen of PEO, where a 1100 cm -1 broad band corresponds to COC stretching and severe deformation occurs. A spectral band at ˜623 cm -1 corresponds to the ClO 4- anion and shows the growth of a shoulder at a higher wave number with increasing salt content. The apparent new envelope at ˜634.5 cm -1 clearly indicates ClO 4--Mg 2+ ion pairing. Ionic conductivity increases with salt content, and is optimized at 15 wt.% Mg salt (O:Mg ratio 28:1). The decrease in ion conductivity at higher salt contents is due to ion-ion association, which leads to ion pair formation (i.e. aggregation of ionic salt) and retards the motion of ions.

  13. Use of Manganese(II)-Schiff Base Complexes for Carrying Polar Organometallics and Inorganic Ion Pairs.

    Gallo, Emma; Solari, Euro; Floriani, Carlo; Chiesi-Villa, Angiola; Rizzoli, Corrado


    This report concerns the carrier properties of [Mn(acacen)]-derived compounds toward polar organometallics, inorganic ion pairs, and salts. Such properties are the consequence of Mn(II) behaving as a Lewis acid and the O&arcraise;O bite of the bidentate Schiff base ligand toward alkali cations. The starting compounds, which occur in a dimeric form, [Mn(acac-L-en)](2) [L' = CH(2)CH(2) (1); L" = C(6)H(10) (2); L"' = R,R-C(6)H(10) (3)] have been synthesized either via a metathesis reaction from MnCl(2) or using [Mn(3)Mes(6)]. The reaction of 1-3 with lithium organometallics allowed the isolation of [Mn(acac-L-en)(R)Li(DME)] [R = Me, L = L' (4); R = Ph, L = L' (5); R = Mes, L = L' (6); R = Me, L = L" (7); R = Me, L = L"' (8)] as metalated forms, where the alkyl or aryl group is sigma-bonded to Mn(II), while the lithium cation is anchored to the Schiff base ligand. The metalated forms 4-8 react with PhCHO to give the corresponding lithium alkoxide, which remains bound in its ion-pair form to the [Mn(acacen)] skeleton in [Mn(2)(acac-L'-en)(2)Li(2)(OCH(Ph)Me)(2)](n)() (9). The use of 8, which has a chiral bridge across two nitrogen atoms, did not lead to a significant asymmetric induction in the reaction with PhCHO, because of the long separation between the lithium cation and the stereogenic center. The metalated form 4 was able to transfer the methyl group to the nitrile function to give the corresponding lithium-imide which then remains bonded to [Mn(acacen)] as the ion pair in a dimeric structure, as revealed for [Mn(2)(acac-L'-en)(2)Li(2)(DME){N=C(Ph)Me}(2)](n)() (10). Their reaction with 1 appears to depend on the steric bulkiness of the alkyl group in NaOR, resulting in either monomeric adducts, i.e. in [Mn(acac-L'-en)(2,6-Bu(t)(2)C(6)H(3)O)Na(DME)(2)] (11.2DME), or polymeric structures, like in [Mn(acac-L'-en)Na(DME)(&mgr;-OEt)](n)() (13). All the dimeric units reported in this paper show a slight antiferromagnetic coupling between the two Mn(II) assisted by

  14. Methylene blue, curcumin and ion pairing nanoparticles effects on photodynamic therapy of MDA-MB-231 breast cancer cell.

    Hosseinzadeh, Reza; Khorsandi, Khatereh


    The aim of current study was to use methylene blue-curcumin ion pair nanoparticles and single dyes as photosensitizer for comparison of photodynamic therapy (PDT) efficacy on MDA-MB-231 cancer cells, also various light sources effect on activation of photosensitizer (PS) was considered. Ion pair nanoparticles were synthesized using opposite charge ions precipitation and lyophilized. The PDT experiments were designed and the effect of PSs and light sources (Red LED (630nm; power density: 30mWcm(-2)) and blue LED (465nm; power density: 34mWcm(-2))) on the human breast cancer cell line were examined. The effect of PS concentration (0-75μg.mL(-1)), incubation time, irradiation time and light sources, and priority in irradiation of blue or red lights were determined. The results show that the ion pairing of methylene blue and curcumin enhance the photodynamic activity of both dyes and the cytotoxicity of ion pair nanoparticles on the MDA-231 breast cancer cell line. Blue and red LED light sources were used for photo activation of photosensitizers. The results demonstrated that both dyes can activate using red light LED better than blue light LED for singlet oxygen producing. Nano scale ion pair precipitating of methylene blue-curcumin enhanced the cell penetrating and subsequently cytotoxicity of both dyes together. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Structural modifications of dicationic acetylcholinesterase reactivators studied under ion-pairing mechanism in reversed-phase liquid chromatography.

    Radulescu, Medeea; Kuca, Kamil; Musilek, Kamil; David, Victor


    A study focused on the chromatographic behavior of several acetylcholinesterase reactivators under ion-pairing mechanism is reported. Among these reactivators, dicationic oximes and carbamoyl-based pyridinium congeners were studied, which form ion pairs with alkylsulfonate anions. This mechanism was studied for some major experimental parameters, such as the chain length of the ion-pairing agent added to the aqueous phase, its concentration, temperature, and nature of the organic modifier from mobile phase. Retention data showed one or two possibilities of forming ion pairs and the tautomerism of the studied reactivators, for different pH values of the aqueous component. Double sigmoid shapes were obtained for the studied compounds for the dependence between retention factor and pH, indicating the possibility of one or two tautomeric equilibria: at pH close to 7 these compounds are not stable as dicationic species and they participate in the retention process as nitroso forms, which are not able to form ion pairs with alkylsulfonates. The dependences of the retention factor on the organic modifier content from mobile phase were linear. Two complementary theoretical models were used to explain the functional dependences for the retention data on the experimental parameters.

  16. Rate theory of solvent exchange and kinetics of Li(+) - BF4 (-)/PF6 (-) ion pairs in acetonitrile.

    Dang, Liem X; Chang, Tsun-Mei


    In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li(+) and the kinetics of ion pairings in lithium-ion batteries (LIBs). We report one of the first computer simulations of the exchange dynamics around solvated Li(+) in acetonitrile (ACN), which is a common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li(+)-[BF4] and Li(+)-[PF6] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li(+). We calculate exchange rates using transition state theory and weighted them with the transmission coefficients determined by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li(+)-[BF4] and Li(+)-[PF6] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems.

  17. Effects of ionic strength and ion pairing on (plant-wide) modelling of anaerobic digestion

    Solon, Kimberly; Flores Alsina, Xavier; Mbamba, Christian Kazadi


    ) and ion pairing on modelling of anaerobic digestion processes in such plant-wide models of wastewater treatment. Using the BSM2 as a case study with a number of model variants and cationic load scenarios, this paper presents the effects of an improved physico-chemical description on model predictions....... The paper describes: 1) how the anaerobic digester performance is affected by physico-chemical corrections; 2) the effect on pH and the anaerobic digestion products (CO2, CH4 and H2); and, 3) how these variations are propagated from the sludge treatment to the water line. Results at high ionic strength......Plant-wide models of wastewater treatment (such as the Benchmark Simulation Model No. 2 or BSM2) are gaining popularity for use in holistic virtual studies of treatment plant control and operations. The objective of this study is to show the influence of ionic strength (as activity corrections...

  18. Probing ion-specific effects on aqueous acetate solutions: Ion pairing versus water structure modifications

    Tristan Petit


    Full Text Available The effect of monovalent cations (Li+, K+, NH4+, Na+ on the water structure in aqueous chloride and acetate solutions was characterized by oxygen K-edge X-ray absorption spectroscopy (XAS, X-ray emission spectroscopy, and resonant inelastic X-ray scattering (RIXS of a liquid microjet. We show ion- and counterion dependent effects on the emission spectra of the oxygen K-edge, which we attribute to modifications of the hydrogen bond network of water. For acetates, ion pairing with carboxylates was also probed selectively by XAS and RIXS. We correlate our experimental results to speciation data and to the salting-out properties of the cations.

  19. Two state electron model for geminate recombination of electron-ion pairs in liquid isooctane

    Lukin, L.V., E-mail: [Institute of Energy Problems of Chemical Physics (Branch), Russian Academy of Sciences, Chernogolovka, P.O. Box 56, Moscow oblast 142432 (Russian Federation); Yakovlev, B.S. [Institute of Energy Problems of Chemical Physics (Branch), Russian Academy of Sciences, Chernogolovka, P.O. Box 56, Moscow oblast 142432 (Russian Federation)


    Graphical abstract: M + n . h{nu} {yields} mobile electron {yields} trapped electron {yields} free charges. Research highlights: {yields} Electrons produced by ionization of liquid alkanes are trapped near positive ions. {yields} The recombination kinetics was expressed in terms of a trapped electron life time. {yields} Transient absorption after the ionizing pulse was analyzed for liquid isooctane. {yields} The life time of trapped electrons was found. - Abstract: Recombination kinetics of geminate electron-ion pairs is considered in the framework of the two state model for electron transport in liquid hydrocarbons. It is shown that the model well reproduces recent experimental data on the subpicosecond geminate recombination obtained in liquid isooctane. The life time of electrons in a localized state in isooctane is estimated to lie in the range between 0.14 ps and 0.57 ps at room temperature.

  20. Simultaneous determination of adenine and guanine in ruminant bacterial pellets by ion-pair HPLC.

    García del Moral, Pilar; Arín, María Jesús; Resines, José Antonio; Díez, María Teresa


    An ion-pair reversed-phase high-performance liquid chromatography with gradient elution and UV detection was used to measure adenine (A) and guanine (G) in lyophilized bacterial pellets from ruminants using allopurinol as internal standard. The separation was performed on a Symmetry C18 column and the detection was monitored at 280 nm. Calibration curves were found to be linear in the concentration range from 5 to 50 mg/l with correlation coefficients (r2)>0.999. Mean recoveries of A and G standards added to bacterial samples were 102.2 and 98.2, respectively. The method proposed yielded sharp, well-resolved peaks within 25 min and was successfully applied for the determination of A and G in bacterial pellets.

  1. Descriptors for ions and ion-pairs for use in linear free energy relationships.

    Abraham, Michael H; Acree, William E


    The determination of Abraham descriptors for single ions is reviewed, and equations are given for the partition of single ions from water to a number of solvents. These ions include permanent anions and cations and ionic species such as carboxylic acid anions, phenoxide anions and protonated base cations. Descriptors for a large number of ions and ionic species are listed, and equations for the prediction of Abraham descriptors for ionic species are given. The application of descriptors for ions and ionic species to physicochemical processes is given; these are to water-solvent partitions, HPLC retention data, immobilised artificial membranes, the Finkelstein reaction and diffusion in water. Applications to biological processes include brain permeation, microsomal degradation of drugs, skin permeation and human intestinal absorption. The review concludes with a section on the determination of descriptors for ion-pairs.

  2. Determination of synthetic food dyes in commercial soft drinks by TLC and ion-pair HPLC.

    de Andrade, Francisca Ivani; Florindo Guedes, Maria Izabel; Pinto Vieira, Ícaro Gusmão; Pereira Mendes, Francisca Noélia; Salmito Rodrigues, Paula Alves; Costa Maia, Carla Soraya; Marques Ávila, Maria Marlene; de Matos Ribeiro, Luzara


    Synthetic food colourings were analyzed on commercial carbonated orange and grape soft drinks produced in Ceará State, Brazil. Tartrazine (E102), Amaranth (E123), Sunset Yellow (E110) and Brilliant Blue (E133) were extracted from soft drinks using C18 SPE and identified by thin layer chromatography (TLC), this method was used to confirm the composition of food colouring in soft drinks stated on label. The concentration of food colouring in soft drink was determined by ion-pair high performance liquid chromatography with photodiode array detection. The results obtained with the samples confirm that the identification and quantification methods are recommended for quality control of the synthetic colours in soft drinks, as well as to determine whether the levels and lables complies with the recommendations of food dyes legislation.

  3. Development of a molecularly imprinted polymer for pyridoxine using an ion-pair as template.

    Alizadeh, Taher


    One of the main challenges in the molecularly imprinted polymers (MIP) field is the proper MIP design for water-soluble compounds because of appearance of serious drawbacks in polar solvents and insolubility of those compounds in non-polar solvents which are commonly used for MIP synthesis. In this work a novel and simple method for synthesis of molecularly imprinted polymers for a water-soluble compound was introduced. Pyridoxine was chosen as a target molecule and the ion-pair complex formed between pyridoxine ion (Py(+)) and dodecyl sulfate ion (DS(-)) was transferred into the chloroform via liquid-liquid extraction. Then polymerization was carried out in chloroform. The molecular mechanics and density functional theory were proposed to screen proper monomer. Binding energy, DeltaE, of a template and a monomer as a measure of their interaction was considered. Ion-pair [Py(+)-DS(-)] was supposed as a template molecule and acrylic acid, methacrylic acid, allyamine, vinylpridine and 2-hydroxy ethyl methacrylate were as tested monomers. The MIP synthesized using acrylic acid showed the highest selectivity to pyridoxine as predicted from the DeltaE calculation. The obtained MIP showed very high affinity against vitamin B6 in comparison to non-imprinted polymers (NIP). It was proved that the obtained MIP with introduced method was much better than that prepared in methanol as porogen. It was showed that the MIP prepared by this new method could be used as an adsorber for extraction and determination of pyridoxine in real and synthetic samples.

  4. Thermodynamics of Ion Pair Formations Between Charged Poly(Amino Acid)s.

    Petrauskas, Vytautas; Maximowitsch, Eglė; Matulis, Daumantas


    Electrostatic interactions between the positively and negatively charged amino acids in proteins play an important role in macromolecular stability, binding, and recognition. Numerous amino acids in proteins are ionizable and may exist in negatively (e.g., Glu, Asp, Cys, Tyr) or positively (e.g., Arg, Lys, His, Orn) charged form dependent on pH and their pKas. In this work, isothermal titration calorimetry was used to determine the average standard values of thermodynamic parameters (the Gibbs free energy, enthalpy, entropy, and the heat capacity) of interaction between the positively charged amino acid homopolymers (polyarginine, polylysine, and polyornithine) and the negatively charged homopolymers (polyaspartic and polyglutamic acids). These values are of potential use in the computational models of interacting proteins and other biological macromolecules. The study showed that oppositely charged poly(amino acid)s bound each other with the stoichiometry of one positive to one negative charge. Arginine bound to the negatively charged amino acids with exothermic enthalpy and higher affinity than lysine. This result also suggests that positive charges in proteins should not be considered entirely equivalent if carried by lysine or arginine. The difference in binding energy of arginine and lysine association with the negatively charged amino acids was attributed to the enthalpy of the second ionic hydrogen bond formation between the guanidine and carboxylic groups. Despite the favorable enthalpic contribution, all such ion pair formation reactions were largely entropy-driven. Consistent with previously observed ionic interactions, the positive heat capacity was always observed during the amino acid ion pair formation.

  5. A Network Approach to Unravel Correlated Ion Pair Dynamics in Protic Ionic Liquids. The Case of Triethylammonium Nitrate

    Zentel, Tobias


    The intermolecular interactions in the title compound are investigated using self-consistent charge density functional based tight binding molecular dynamics. Emphasis is put on the analysis of correlated motions of ion pairs using ideas of network theory. At equilibrium such correlations are not very pronounced on average. However, there exist sizeable local correlations for cases where two cations share the same anion via two NHO-hydrogen bonds. The effect of an external perturbation, which artificially introduces a sudden local heating of an NH-bond, is investigated using nonequilibrium molecular dynamics. Here, it is found that the average N-H bond vibrational relaxation time is about 5.3 ~ps. This energy redistribution is rather nonspecific with respect to the ion pairs and does not lead to long-range correlations spreading from the initially excited ion pair.

  6. Rapid and simultaneous determination of imidazolium and pyridinium ionic liquid cations by ion-pair chromatography using a monolithic column

    Xu Huang; Hong Yu; Ying Jie Dong


    A method for rapid and simultaneous determination of imidazolium and pyridinium ionic liquid cations by ion-pair chromatography with ultraviolet detection was developed.Chromatographic separations were performed on a reversed-phase silica-based monolithic column using 1-heptanesulfonic acid sodium-acetonitrile as mobile phase.The effects of ion-pair reagent and acetonitrile concentration on retention of the cations were investigated.The retention times of the cations accord with carbon number rule.The method has been successfully applied to the determination of four ionic liquids synthesized by organic chemistry laboratory.

  7. Ion pair formation as a possible mechanism for the enhancement effect of lauric acid on the transdermal permeation of ondansetron.

    Dimas, Dimitrios A; Dallas, Paraskevas P; Rekkas, Dimitrios M


    Transdermal application can be an alternative drug delivery route for ondansetron, an antiemetic drug. Previous studies found that fatty acids, namely oleic and lauric, were the most effective penetration enhancers. The aim of this study was to investigate the formation of an ion pair between ondansetron and lauric acid as a possible mechanism of its enhancing action. Several techniques were used to reveal the formation of an ion pair complex. Partitioning experiments, where the n-octanol/water coefficient was measured, showed an increase in the distribution coefficient in the presence of the acid, possibly as a result of the formation of more lipophilic ion pairs between the charged molecules of ondansetron and lauric acid. Further evidence of complex formation between ondansetron and lauric acid, was gained from the 13C-nuclear magnetic resonance (13C-NMR) spectra of ondansetron, lauric acid, and their mixture (molar ratio 1:1). The NMR spectra revealed alterations to the magnetic environment of the carbon atoms adjacent to the ionized group, which are the carbonyl group of the acid and the nitrogen of the imidazole ring of ondansetron. This evidence substantiates the theory of ion pair formation. Finally, thermal analysis of the binary mixtures of ondansetron and lauric acid revealed the formation of an additional compound, with different melting point from pure ondansetron and lauric acid, which is thermodynamically favored.

  8. On the non-linearity of the master equation describing spin-selective radical-ion-pair reactions

    Kominis, I. K.


    We elaborate on the physical meaning of the non-linear master equation that was recently derived to account for spin-selective radical-ion-pair reactions. Based on quite general arguments, we show that such a non-linear master equation is indeed to be expected.

  9. Hydrogen Bonding in Ion-pair Molecules in Vapors over ionic liquids, studied by Raman Spectroscopy and ab initio Calculations

    Berg, Rolf W.

    -H-Br] [ref 2] and (3) the 1-methylimidazolium ethano-ate, [mim-H-O2CCH3] found [ref 3] to have a less likely existence in the vapor of the corresponding liquid in ampouls at ~200°C (Fig. 2). Experimental Raman results will be compared to ab initio calculated spectra. Fig. 1. Likely gaseous ion pair molecule...

  10. Applications of NMR diffusion methods with emphasis on ion pairing in inorganic chemistry: a mini-review.

    Pregosin, Paul S


    This mini-review provides a brief overview of the use of NMR diffusion methods in connection with estimating molecular weights in solution, recognizing hydrogen bonding and encapsulation processes and, primarily, identifying and estimating the varying degrees of ion pairing. Copyright © 2016 John Wiley & Sons, Ltd.

  11. Determining the association constant and adsorption properties of ion pairs in water by fitting surface tension data.

    Pradines, Vincent; Lavabre, Dominique; Micheau, Jean-Claude; Pimienta, Véronique


    Association constants and adsorption parameters of tetraalkylammoniumdodecyl sulfate (TAADS) ion pairs in water were determined. We have analyzed water/air surface tension measurements obtained for mixtures of sodium dodecyl sulfate (SDS) and tetraalkylammonium bromide of increasing chain lengths (TMAB, TEAB, TPAB, and TBAB). To reproduce the experimental isotherms, we coupled the association equilibrium of the ion pairs to the equations proposed by Fainerman and co-workers to model the adsorption of binary mixtures of surfactants (SDS and TAADS) with different molar areas at a nonideal surface layer. The parameters found showed that the model is not convenient to describe the effect of the addition of TMAB but a clear coherency was obtained for the three longer compounds. Ranging from TEADS to TBADS increasing hydrophobic interactions give rise to a higher associability but to a lower surface activity. Self-interactions coefficients extracted by the fitting procedure confirmed the importance of attractive interactions between the ion pairs. The calculated surface coverage showed that in every case the compound mainly adsorbed at the interface was the ion pair. For TBADS strong attractive interactions result in a phase transition at very low concentration.

  12. Solid-liquid stable phase equilibria of the ternary systems MgCl2 + MgB6O10+ H2O AND MgSO4 + MgB6O10 + H2O at 308.15 K

    Lingzong Meng


    Full Text Available The solubilities and the relevant physicochemical properties of the ternary systems MgCl2 + MgB6O10 + H2O and MgSO4 + MgB6O10 + H2O at 308.15 K were investigated using an isothermal dissolution method. It was found that there is one invariant point, two univariant curves, and two crystallization regions of the systems. The systems belong to a simple co-saturated type, and neither double salts nor solid solutions were found. Based on the extended HW model and its temperature-dependent equations, the single-salt Pitzer parameters β(0, β(1, β(2 and CØ for MgCl2, MgSO4, and Mg(B6O7(OH6, the mixed ion-interaction parameters θCl,B6O10, θSO4,B6O10, ΨMg,Cl,B6O10, ΨMg,SO4,B6O10 of the systems at 308.15 K were fitted, In addition, the average equilibrium constants of the stable equilibrium solids at 308.15 K were obtained by a method using the activity product constant. Then the solubilities of the ternary systems are calculated. The calculated solubilities agree well with the experimental values.

  13. Halogen bonding interactions between brominated ion pairs and CO2 molecules: implications for design of new and efficient ionic liquids for CO2 absorption.

    Zhu, Xiang; Lu, Yunxiang; Peng, Changjun; Hu, Jun; Liu, Honglai; Hu, Ying


    In recent years, several novel halogenated liquids with characteristics of ionic liquids (ILs) were reported. To explore their performance in the absorption of CO(2), in this work, quantum chemical calculations at DFT level have been carried out to investigate halogen bonding interactions between experimentally available brominated ion pairs and CO(2) molecules. It is shown that, as compared to B3LYP, the functional PBE yields geometrical and energetic data more close to those of MP2 for cation-CO(2) systems. The cation of brominated ILs under study can interact with CO(2) molecules through Br···O interactions, possibly making an important impact on the physical solubility of CO(2) in brominated ILs. The optimized geometries of the complexes of the ion pair with CO(2) molecules are quite similar to those of the corresponding complexes of the cation, especially for the essentially linear C-Br···O contacts. However, much weaker halogen bonds are predicted in the former systems, as indicated by the longer intermolecular distances and the smaller interaction energies. Charges derived from NBO analysis reveal the origin of the different optimized conformations and halogen bonding interactions for the CO(2) molecule. Based on the electrostatic potential results, the substitution of hydrogen atoms with fluorine atoms constituting the cation is then applied to enhance halogen bond strength. The QTAIM analysis further validates the existence of halogen bonding interaction in all complexes. The topological properties at the halogen bond critical points indicate that the Br···O interactions in the complexes are basically electrostatic in nature and belong to conventional weak halogen bonds. This study would be helpful for designing new and effective ILs for CO(2) physical absorption.

  14. Micro-Raman studies on the kinetics of the exchange between H2O and D2O of MgSO4 droplets%硫酸镁微液滴水和重水交换动力学的微区拉曼研究

    李开开; 曾光; 郭郁葱; 张韫宏


    本文利用微区拉曼技术,研究硫酸镁液滴水和重水交换的动力学.在低湿度时,由接触离子对连接形成的链状结构使硫酸镁液滴表面形成胶态结构,阻碍其与环境之间的水交换,造成表面和内部的结构差异.拉曼光谱的高空间分辨能力为观测这一特殊的表面结构提供了便利.沉积在聚四氟乙烯疏水基底上的硫酸镁重水液滴呈球形,可以实现对液滴表面和中心的两次聚焦,为研究水从液滴表面逐步扩散到中心的动力学过程提供了可能.同时,利用拉曼光谱的时间分辨能力,可以观测硫酸镁微液滴中水和重水的交换过程,从而揭示传质受阻硫酸镁液滴中水的扩散机制.%In this paper, we will reveal the kinetics of evaporation of MgSO4/D2O droplets and the exchange between H2O and D2O in the mass transfer-limited MgSO4 droplets by micro-Raman spectroscopy. The gel layer causes a delay of the droplet in response to the change of ambient relative humidity, and results in the structural difference between the surface and the centre of MgSO4 droplets. Micro-Raman technique provides a good approach for detecting the surface structure in virtue of its high spatial resolution. In particular, as droplets are likely to maintain a spherical shape on a hydrophobic Teflon substrate, the laser beam can be tightly focused twice on the surface and in the center of the typically spherical droplets, thus the Raman spectra of the surface and the centre of the droplet can be obtained respectively and the diffusion of water in the droplet can be monitored. On the other hand, with an accumulation time of less than one second in a static mode, micro-Raman spectra of droplets can be obtained with high signal-to-noise ratio. The temporal scale allows the observation on the exchange of H2O and D2O in MgSO4 droplets with a slow exchanging rate, which is critical to understand the kinetics of the e-vaporation and condensation of water in mass transfer-limited MgSO4 droplet.

  15. Ion-pair HPLC method for the quantification of metformin in human urine

    Eva Troja


    Full Text Available The aim of this study was to develop and validate a selective and sensitive ion-pairing HPLC–UV method for the determination of metformin in human urine using a conventional reversed-phase column. The bioanalytical method was carried out using a RP-C18 column (250×4.0 mm; 5 μm. A mobile phase consisting of acetonitrile and 10 mM sodium phosphate buffer (pH=6.0, 30:70 v/v and sodium dodecyl sulfate (0.3% was pumped at an isocratic flow rate of 1.00 mL/minute and quantification was achieved at 236 nm using using a UV/VIS DAD. The calibration curves were linear (r2 >0.999 in the concentration ranges of 62.5–2000 μg/mL for metformin in urine. LOD and LOQ were found to be 12 μg/mL and 35 μg/mL, respectively. The method was found to be rapid, precise and accurate for quantification of metformin in human urine. This method was successfully applied to a pharmacokinetic study of humans through oral administration.

  16. Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

    Peter Hesemann


    Full Text Available The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA, mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the “anionic templating” strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

  17. Ion-pair dissociation of highly excited carbon clusters: Size and charge effects

    Launoy, Thibaut; Béroff, Karine; Chabot, Marin; Martinet, Guillaume; Le Padellec, Arnaud; Pino, Thomas; Bouneau, Sandra; Vaeck, Nathalie; Liévin, Jacques; Féraud, Géraldine; Loreau, Jérôme; Mahajan, Thejus


    We present measurements of ion-pair dissociation (IPD) of highly excited neutral and ionized carbon clusters Cn=2 -5 (q =0 -3 )+. The tool for producing these species was a high-velocity collision between Cn+ projectiles (v =2.25 a.u.) and helium atoms. The setup allowed us to detect in coincidence anionic and cationic fragments, event by event, leading to a direct and unambiguous identification of the IPD process. Compared with dissociation without anion emission, we found typical 10-4 IPD rates, not depending much on the size and charge of the (n ,q ) species. Exceptions were observed for C2+ and, to a lesser extent, C43 + whose IPDs were notably lower. We tentatively interpret IPDs of C2+ and C3+ by using a statistical approach based on the counting of final states allowed by energetic criteria. The model is able to furnish the right order of magnitude for the experimental IPD rates and to provide a qualitative explanation of the lower IPD rate observed in C2+.

  18. How Ions Arrange in Solution: Detailed Insight from NMR Spectroscopy of Paramagnetic Ion Pairs.

    Damjanović, Marko; Morita, Takaumi; Horii, Yoji; Katoh, Keiichi; Yamashita, Masahiro; Enders, Markus


    Ion pairing between the paramagnetic anion [Tb(obPc)2 ](-) (obPc=2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato), which has a very large magnetic anisotropy, with various diamagnetic counterions [P(Ph)4 ](+) (1 a), [As(Ph)4 ](+) (1 b), bis(triphenylphosphine)iminium ([PPN](+) , 1 c) and tetra-n-butylammonium ([TBA](+) , 1 d) was studied by means of (1) H, (13) C, (14) N, and (31) P NMR spectroscopy in solution at various temperatures. The influence of the paramagnetic anion on the NMR spectroscopy properties of the diamagnetic cations allowed a detailed insight into the distances and relative orientations of the paired ions. Isotropic tumbling models for the description of the quaternary cations are inaccurate, particularly for [TBA](+) with its flexible butyl chains. The effects of temperature and concentration were also assessed. The advantage of this technique is that relatively large distances and the orientation between molecules or ions in solution can be studied. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Amino acid anions in organic ionic compounds. An ab initio study of selected ion pairs.

    Benedetto, A; Bodo, E; Gontrani, L; Ballone, P; Caminiti, R


    The combination of amino acids in their deprotonated and thus anionic form with a choline cation gives origin to a new and potentially important class of organic ionic compounds. A series of such neutral ion pairs has been investigated by first principle methods. The results reveal intriguing structural motives as well as regular patterns in the charge distribution and predict a number of vibrational and optical properties that could guide the experimental investigation of these compounds. The replacement of choline with its phosphocholine analogue causes the spontaneous reciprocal neutralization of cations and anions, taking place through the transfer of a proton between the two ions. Systems of this kind, therefore, provide a wide and easily accessible playground to probe the ionic/polar transition in organic systems, while the easy transfer of H(+) among neutral and ionic species points to their potential application as proton conductors. The analysis of the ab initio data highlights similarities as well as discrepancies from the rigid-ions force-field picture and suggests directions for the improvement of empirical models.

  20. Interplay between alkyl chain asymmetry and cholesterol addition in the rigid ion pair amphiphile bilayer systems

    Huang, Fong-yin; Chiu, Chi-cheng


    Ion pair amphiphile (IPA), a molecular complex composed of a pair of cationic and anionic surfactants, has been proposed as a novel phospholipid substitute. Controlling the physical stability of IPA vesicles is important for its application developments such as cosmetic and drug deliveries. To investigate the effects of IPA alkyl chain combinations and the cholesterol additive on the structural and mechanical properties of IPA vesicular bilayers, we conducted a series of molecular dynamics studies on the hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS) and dodecyltrimethylammonium-hexadecylsulfate (DTMA-HS) IPA bilayers with cholesterol. We found that both IPA bilayers are in the gel phase at 298 K, consistent with experimental observations. Compared with the HTMA-DS system, the DTMA-HS bilayer has more disordered alkyl chains in the hydrophobic region. When adding cholesterol, it induces alkyl chain ordering around its rigid sterol ring. Yet, cholesterol increases the molecular areas for all species and disturbs the molecular packing near the hydrophilic region and the bilayer core. Cholesterol also promotes the alkyl chain mismatch between the IPA moieties, especially for the DTMA-HS bilayer. The combined effects lead to non-monotonically enhancement of the membrane mechanical moduli for both IPA-cholesterol systems. Furthermore, cholesterol can form H-bonds with the alkylsulfate and thus enhance the contribution of alkylsulfate to the overall mechanical moduli. Combined results provide valuable molecular insights into the roles of each IPA component and the cholesterol on modulating the IPA bilayer properties.

  1. Extractive Spectrophotometric Determination of Bismuth(III in Water Using Some Ion Pairing Reagents

    Abdulaziz S. Bashammakh


    Full Text Available Two novel and low cost liquid-liquid extraction methods for the separation of bismuth(III at trace level from aqueous medium have been developed. The two methods were based upon the formation of yellow colored ternary complex ion associates of tetraiodobismuth(III complex anion, BiI4- with the ion-pairing reagent 2,3,5-tetraphenyltetrazoliumchloride (Tz+.Cl– and 1, 10 phenanthroline (Phen in sulfuric acid medium. The effect of various parameters e.g. pH, organic solvent, shaking time, etc. on the preconcentration of bismuth(III from the aqueous media by the reagent was investigated. The developed colored complex ion associates [Tz+.BiI4-] and [Phen+.BiI4-] were extracted quantitatively into acetone-chloroform (1:1v/v and methyliso- butylketone (MIBK, respectively. The compositions of the formed complex ion associates [Tz+.BiI4-] and [Phen+.BiI4-] were determined by the Job's method at 500 and 490 nm, respectively. The plots of bismuth(III concentration (0-17 μg mL-1 versus absorbance of the associates at 500 and 490 nm were linear with good correlation coefficient (R2=0.998. The developed method of the ion associate [Tz+.BiI4-] two methods was applied successfully for the analysis of bismuth in water.

  2. Rate Theory of Ion Pairing at the Water Liquid–Vapor Interface

    Dang, Liem X.; Schenter, Gregory K.; Wick, Collin D.


    There is overwhelming evidence that certain ions are present near the vapor–liquid interface of aqueous salt solutions. Despite their importance in many chemical reactive phenomena, how ion–ion interactions are affected by interfaces and their influence on kinetic processes is not well understood. Molecular simulations were carried out to exam the thermodynamics and kinetics of small alkali halide ions in the bulk and near the water vapor–liquid interface. We calculated dissociation rates using classical transition state theory, and corrected them with transmission coefficients determined by the reactive flux method and Grote-Hynes theory. Our results show that, in addition to affecting the free energy of ions in solution, the interfacial environments significantly influence the kinetics of ion pairing. The results obtained from the reactive flux method and Grote-Hynes theory on the relaxation time present an unequivocal picture of the interface suppressing ion dissociation. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.

  3. Mapping of low molecular weight heparins using reversed phase ion pair liquid chromatography-mass spectrometry.

    Li, Daoyuan; Chi, Lequan; Jin, Lan; Xu, Xiaohui; Du, Xuzhao; Ji, Shengli; Chi, Lianli


    Low molecular weight heparins (LMWHs) are structurally complex, highly sulfated and negatively charged, linear carbohydrate polymers prepared by chemical or enzymatic depolymerization of heparin. They are widely used as anticoagulant drugs possessing better bioavailability, longer half-life, and lower side effects than heparin. Comprehensive structure characterization of LMWHs is important for drug quality assurance, generic drug application, and new drug research and development. However, fully characterization of all oligosaccharide chains in LMWHs is not feasible for current available analytical technologies due to their structure complexity and heterogeneity. Fingerprinting profiling is an efficient way for LMWHs' characterization and comparison. In this work, we present a simple, sensitive, and powerful analytical approach for structural characterization of LMWHs. Two different LMWHs, enoxaparin and nadroparin, were analyzed using reversed phase ion pair electrospray ionization mass spectrometry (RPIP-ESI-MS). More than 200 components were identified, including major structures, minor structures, and process related impurities. This approach is robust for high resolution and complementary fingerprinting analysis of LMWHs.

  4. An operationally flexible fuel cell based on quaternary ammonium-biphosphate ion pairs

    Lee, Kwan-Soo; Spendelow, Jacob S.; Choe, Yoong-Kee; Fujimoto, Cy; Kim, Yu Seung


    Fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100 ∘C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180 ∘C however, these devices degrade when exposed to water below 140 ∘C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibit stable performance at 80-160 ∘C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems.

  5. Spectroscopic Observation of Water-Mediated Deformation of the CARBOXYLATE-M2+ (M= Mg, Ca) Contact Ion Pair

    Kelleher, Patrick J.; DePalma, Joseph W.; Johnson, Mark


    The binding of alkaline earth dications to the biologically relevant carboxylate ligand has previously been studied using vibrational sum frequency generation (VSFG) spectroscopy of the air-water interface, infrared multiple photon dissociation (IRMPD) spectroscopy of clusters, and DFT methods. These results suggest the presence of both monodentate and bidentate binding motifs of the M2+ ions to the cayboxyl head groups depending on the extent of solvation. We revisit these systems using vibrational predissociation spectroscopy to measure the gas-phase vibrational spectra of the D2-tagged microhydrated [MgOAc(H2O)n=1-5]+ and [CaOAc(H2O)n=1-6]+ clusters. The spectra show that [MgOAc(H2O)n]+ switches from bidentate to monodentate binding promptly at n = 5, while [CaOAc(H2O)n]+ retains its bidentate attachment such that the sixth water molecule initiates the second solvation shell. The difference in binding behavior between these two divalent metal ions is analyzed in the context of the local acidity of the solvent water molecules and the strength of the metal-carboxylate and metal-water interactions. This cluster study provides insight into the chemical physics underlying the unique and surprising impacts of Mg2+ and Ca2+ on the chemistry mediated by sea spray aerosols. Funding for this work was provided by the NSF's Center for Aerosol Impacts on Climate and the Environment.

  6. Separation of basic oligopeptides by ion-pairing reversed-phase chromatography

    Xie, Wenchun

    The present thesis consist of five chapters. Chapter I introduces background information on the ion-pairing reversed-phase chromatography and liquid chromatography in the critical condition. Chapter II decribes our study on the isocratic separation of oligolysine (dp = 2 to 8) using a fixed content of acetonitrile (ACN) (23%) and different concentrations of HFBA in the mobile phase (0.6-30.6 mM) on a Waters XBridge Shield RP18® column. We found that the retention time of oligolysine increases as the dp increases, because of an increased number of HFBA bound to the peptides. Furthermore, when [HFBA] increased, the retention time increased at different rates. The greater the dp, the faster the rate. Based on a closed pairing model that presumes an equilibrium between an unpaired state and the paired state with a fixed number of HFBA molecules, an equation was derived for the retention factor of oligolysine. In Chapter III, we compare retention behaviors of oligolysine (dp = 2 to 8) and oligoarginine (dp = 2 to 8) when they are separated on the Waters XBridge Shield RP18® using fixed a ACN content (23%) and difference concentrations of HFBA (0.4-30.6 mM) in the mobile phase. The retention time of oligoarginine also increased at different rates as [HFBA] increased. The greater the dp, the faster the rate. The retention time of oligolysine is shorter than that of oligarginine having the dame dp. We applied Eq.1 to analyze the plot of ln k as a function of [HFBA] for each oligopeptide component to obtain the values for n, Kip,m, and βKd,ip. For oligolysine, n increases linearly as dp increase and oligoarginine exhibits an accelerated increase in n as dp rises. The plot of ln βKd,ip against dp followed a linear relationship for both peptides. In Chapter IV, we study the effect of mobile phase composition on the retention of oligolysine (dp = 2 to 8) on the Waters XBridge Shield RP18 ®. The ACN content was changed from 20% to 33% and the HFBA concentration from 0.7 to

  7. 腔增强拉曼技术下的过饱和硫酸镁液滴蒸发动力学初探%Preliminary Assessment of Evaporating Supersaturated MgSO4 Droplet at Low Relative Humidity with Cavity Enhanced Raman Spectroscopy

    陈斯华; 蔡宸; 冷春波; 张韫宏


    This paper is aimed to study the response of a single MgSO4 droplet to the variation of relative humidity through the combination of single beam gradient force optical tweezers and Raman spectroscopy.The evaporation dynamic of a single MgSO4 droplet which is trapped by a single beam gradient force optical tweezers is investigated by varying the relative humidity in a stepwise manner.The measurements of the variation in equilibrium wet droplet size with relative humidity (RH) are made using cavity enhanced Raman scattering(CERS),where the stimulated Raman signals appear at wavelength commensurate to the Whispering Gallery Modes (WGMs) are applied to determine the size of droplet with high precision.This study demonstrates the real time monitoring of MgSO4 droplet size over a RH range that had not previously been explored with aerosol optical tweezers.The results show that the MgSO4 droplet radius variation gradually becomes smaller as the RH=~44% and is greatly depressed when RH lower than 40%,indicating that water evaporation rate of captured MgSO4 droplet is limited at high concentration.On the other hand,the deliquescence of shrinked MgSO4 droplet is not equivalent with the dehumidification process.The re-growth of MgSO4 droplet size is observed to be significantly slower in response to the increase of RH.It is suggested that mass transfer effect caused by the gel formation has contributed to the retardation of water mass transfer.%本文通过单光束梯度力光学镊子-拉曼光谱系统,对硫酸镁单液滴随着相对湿度变化的反应进行了探究.当硫酸镁单液滴被光镊捕获之后,通过相对湿度的梯度变化探究了捕获液滴的蒸发动力学变化.发生在与耳语回音模相称波长的受激拉曼散射可以用来准确地确定液滴半径,因此,可以通过腔增强拉曼散射得到在不同湿度下处于平衡的液滴半径信息.本研究通过光镊对硫酸镁单液滴的实时监测,阐述了在某个相对湿度范围内该液滴的粒径变化的过程和结果,在此之前的硫酸镁吸湿性研究中没有先例.研究结果表明在相对湿度逐渐降低至40%的过程中硫酸镁液滴半径的变化速率逐渐变小.而当相对湿度低于40%时,液滴半径的减小会被严重抑制.这种现象表示在高浓度条件下硫酸镁液滴中水的蒸发扩散速率会降低.另一方面,在蒸发过程后的相对湿度上升过程中,硫酸镁液滴尺寸的增加明显缓慢于湿度增长速度.这一现象显示液滴的尺寸变化是不可逆的.说明胶态的形成导致了传质受阻,从而阻碍了液滴中水分子的交换.

  8. Near Infrared Quantum Cutting Luminescence of Er(3+)/Tm(3+) Ion Pairs in a Telluride Glass.

    Chen, Xiaobo; Li, Song; Hu, Lili; Wang, Kezhi; Zhao, Guoying; He, Lizhu; Liu, Jinying; Yu, Chunlei; Tao, Jingfu; Lin, Wei; Yang, Guojian; Salamo, Gregory J


    The multiphoton near-infrared, quantum cutting luminescence in Er(3+)/Tm(3+) co-doped telluride glass was studied. We found that the near-infrared 1800-nm luminescence intensity of (A) Er(3+)(8%)Tm(3+)(0.5%):telluride glass was approximately 4.4 to 19.5 times larger than that of (B) Tm(3+)(0.5%):telluride glass, and approximately 5.0 times larger than that of (C) Er(3+)(0.5%):telluride glass. Additionally, the infrared excitation spectra of the 1800 nm luminescence, as well as the visible excitation spectra of the 522 nm and 652 nm luminescence, of (A) Er(3+)(8%)Tm(3+)(0.5%):telluride glass are very similar to those of Er(3+) ions in (C) Er(3+)(0.5%):telluride glass, with respect to the shapes of their excitation spectral waveforms and peak wavelengths. Moreover, we found that there is a strong spectral overlap and energy transfer between the infrared luminescence of Er(3+) donor ions and the infrared absorption of Tm(3+) acceptor ions. The efficiency of this energy transfer {(4)I13/2(Er(3+)) → (4)I15/2(Er(3+)), (3)H6(Tm(3+)) → (3)F4(Tm(3+))} between the Er(3+) and Tm(3+) ions is approximately 69.8%. Therefore, we can conclude that the observed behaviour is an interesting multiphoton, near-infrared, quantum cutting luminescence phenomenon that occurs in novel Er(3+)-Tm(3+) ion pairs. These findings are significant for the development of next-generation environmentally friendly germanium solar cells, and near-to-mid infrared (1.8-2.0 μm) lasers pumped by GaN light emitting diodes.

  9. Hydrophobic ion pairing of an insulin-sodium deoxycholate complex for oral delivery of insulin

    Sun S


    Full Text Available Shaoping Sun1–3, Na Liang2, Yoshiaki Kawashima3, Dengning Xia2, Fude Cui21School of Chemistry and Material Science, Heilongjiang University, Harbin, 2School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, China; 3School of Pharmaceutical Science, Aichi Gakuin University, Nissin, JapanAbstract: Insulin was complexed with sodium deoxycholate to form an insulin-sodium deoxycholate complex (Ins-SD-Comp using an hydrophobic ion pairing method in aqueous phase to enhance the liposolubility of insulin. In order to obtain the maximal complexation efficiency, the molar ratio of sodium deoxycholate to insulin was found. The zeta potential method was used to confirm the optimal ratio for formation of Ins-SD-Comp. The structural characteristics of Ins-SD-Comp were assessed using the Fourier transform infrared method. The apparent partition coefficient of insulin increased upon the formation of Ins-SD-Comp. Based on the preliminary study, Ins-SD-Comp was encapsulated into poly(lactide-co-glycolide (PLGA nanoparticles using an emulsion solvent diffusion method. The maximal encapsulation efficiency of Ins-SD-Comp into PLGA nanoparticles was 93.6% ± 2.81%, drug loading was about 4.8% ± 0.32%, and the mean diameter of the nanoparticles was 278 ± 13 nm. Biological activity and in vivo results revealed that the bioactivity of insulin was not destroyed during the preparation process. Ins-SD-Comp-loaded PLGA nanoparticles have the potential to reduce serum glucose levels and increase the oral bioavailability of insulin.Keywords: insulin complex, sodium deoxycholate, nanoparticles, zeta potential, oral bioavailability

  10. The role of ion-pairing in peak deformations in overloaded reversed-phase chromatography of peptides.

    Tarafder, Abhijit; Aumann, Lars; Morbidelli, Massimo


    The paper reports a study on the role of ion-pairing behind peak deformations, e.g. peak splitting and even peak disappearance, during the elution of a peptide at highly overloaded conditions in reversed-phase chromatography. Deformation of component peaks is not uncommon in chromatography. There are reports which discuss their occurrence, but mostly at analytical scale, while their occurrence is quite common also in the preparative scale, as in the case discussed in this work. This paper first describes the conditions leading to peak splitting and peak disappearance of an industrial peptide, then explains the plausible reasons behind such behaviour, and finally with experimental analysis demonstrates the role of ion-pairing in causing such behaviour.

  11. Theoretical Study on the Ion-pair Formation Mechanism for the Li + I2 → Li+ + I2- System

    SUN Xiao-Min; FENG Da-Cheng; CAI Zheng-Ting


    For the Li + I2 →Li+ + I2- system, theoretical study has been performed on the QCISD(T) level by using the ab initio method. The collision complex in ion-pair formation process was found and optimized. These results show that the crossed molecule beam (CMB) experimental phenomenon is verified and the detailed geometry is given for the first time. A mechanism for ion-pair formation was proposed in detail. The position where the collision complex occurs affects the reaction path. Specifically, the process has threshold when the collision complex appeared before the crossing point between the covalent and ionic state potential energy surfaces. On the contrary, the process has no threshold after the crossing point. Theoretically, the title system belongs to the former case.

  12. Importance of the ion-pair interactions in the OPEP coarse-grained force field: parametrization and validation.

    Sterpone, Fabio; Nguyen, Phuong H; Kalimeri, Maria; Derreumaux, Philippe


    We have derived new effective interactions that improve the description of ion-pairs in the OPEP coarse-grained force field without introducing explicit electrostatic terms. The iterative Boltzmann inversion method was used to extract these potentials from all atom simulations by targeting the radial distribution function of the distance between the center of mass of the side-chains. The new potentials have been tested on several systems that differ in structural properties, thermodynamic stabilities and number of ion-pairs. Our modeling, by refining the packing of the charged amino-acids, impacts the stability of secondary structure motifs and the population of intermediate states during temperature folding/unfolding; it also improves the aggregation propensity of peptides. The new version of the OPEP force field has the potentiality to describe more realistically a large spectrum of situations where salt-bridges are key interactions.

  13. Amperometric detection of heavy metal ions in ion pair chromatography at an array of water/nitrobenzene micro interfaces

    Wilke, S. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie; Wang, H. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie; Muraczewska, M. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie; Mueller, H. [Martin-Luther-Univ. Halle-Wittenberg, Merseburg (Germany). Fachbereich Chemie


    A novel amperometric detector for heavy metal ions has been developed and successfully applied for ion pair chromatography. The detector is based on the electrochemical transfer of the metal ions across an array of water/nitrobenzene micro interfaces. The ion transfer is facilitated by the neutral ionophores methylenebis(diphenylphosphineoxide) and methylenebis(di- phenylphosphinesulfide). More than eight metals are separated in less than 15 min on an RP18 column using octyl sulfonate as ion pair reagent. For the heavy metals, the limits of decision are 19(Pb{sup 2+}), 9(Zn{sup 2+}), 9l (Co{sup 2+}), 8(Cd{sup 2+}) and 1.6(Mn{sup 2+}) {mu}g/L. The applicability of the new method for water samples is demonstrated. (orig.). With 3 figs., 2 tabs.

  14. Lamb shift in radical-ion pairs produces a singlet-triplet energy splitting in photosynthetic reaction centers

    Vitalis, K. M.; Kominis, I. K.


    Radical-ion pairs, fundamental for understanding photosynthesis and the avian magnetic compass, were recently shown to be biological open quantum systems. We here show that the coupling of the radical-pair's spin degrees of freedom to its decohering vibrational reservoir leads to a shift of the radical-pair's magnetic energy levels. The Lamb shift Hamiltonian is diagonal in the singlet-triplet basis, and results in a singlet-triplet energy splitting physically indistinguishable from an exchan...

  15. Importance of the Ion-Pair Interactions in the OPEP Coarse-Grained Force Field: Parametrization and Validation

    Sterpone, Fabio; Nguyen, Phuong H; Kalimeri, Maria; Derreumaux, Philippe


    We have derived new effective interactions that improve the description of ion-pairs in the OPEP coarse-grained force field without introducing explicit electrostatic terms. The iterative Boltzmann inversion method was used to extract these potentials from all atom simulations by targeting the radial distribution function of the distance between the center of mass of the side-chains. The new potentials have been tested on several systems that differ in structural properties, thermodynamic sta...

  16. Ion-Pair Complexation with Dibenzo[21]Crown-7 and Dibenzo[24]Crown-8 bis-Urea Receptors.

    Mäkelä, Toni; Kiesilä, Anniina; Kalenius, Elina; Rissanen, Kari


    Synthesis and ion-pair complexation properties of novel ditopic bis-urea receptors based on dibenzo[21]crown-7 (R(1) ) and dibenzo[24]crown-8 (R(2) ) scaffolds have been studied in the solid state, solution, and gas phase. In a 4:1 CDCl3 /[D6 ]DMSO solution, both receptors clearly show positive heterotropic cooperativity toward halide anions when complexed with Rb(+) or Cs(+) , with the halide affinity increasing in order I(-) ion pairs was also observed also in the gas phase by competition experiments with mass spectrometry. A total of eight crystal structures with different rubidium and caesium halides and oxyanions were obtained in addition to the crystal structure of R(2) ⋅BaCl2 . The selectivity observed in solution and in the gas phase is explainable by the conformational differences observed in the crystal structures of ion-pair complexes with R(1) and R(2) . In the solid state, R(1) has an open conformation due to the asymmetric crown-ether scaffold, whereas R(2) has a compact, folded conformation. Computational studies of the ion-pair complexes of R(2) show that the interaction energies of the complexes increase in the order CsI

  17. Ion-pair formation of Bi(III)-iodide with some nitrogenous drugs and its application to pharmaceutical preparations.

    Abdel-Gawad, F M


    A systematic spectrophotometric study on the ion-pair formation of Bi(III)-iodide with amineptine hydrochloride, piribedil and trimebutine maleate is carried out. The optimal experimental conditions pH, concentration of Bi(III) nitrate, potassium iodide; and the nature and amount of organic solvent have been studied. The ion pairs are soluble in 1,2-dichloroethane and the optimum pH range is 2.0-2.8. By application of the methods of Sommer and Job involving non-equimolar solutions, the conditional stability constant (log K') of the Bi(III) piridedil ion pair (1:1) at the optimum pH of 2.4 and an ionic strength (mu) 0.1 M, was found to be 5.436. The validity of Beer's law has been tested in the concentration range 5-50 microg ml(-1) in the organic layer, the relative standard deviation is less than 1%. The method is applied to the determination of these drugs in tablets without interference.

  18. Hydrophobic ion pairing as a method for enhancing structure and activity of lyophilized subtilisin BPN' suspended in isooctane.

    Kendrick, B S; Meyer, J D; Matsuura, J E; Carpenter, J F; Manning, M C


    The use of enzymes in low water environments permits reactions to occur that are difficult or impossible in aqueous solution. In this manner, proteases can be used to form, rather than hydrolyze, ester and amide linkages. Presumably, the native-like structure of the enzyme must remain intact for catalysis to transpire. However, little is known regarding the integrity of the overall structure of lyophilized proteins suspended in organic media. In this study, the structural changes that occur during the freeze-drying process and those effected by suspension in the organic solvent were examined. Using Fourier-transform infrared spectroscopy, the secondary structure of lyophilized subtilisin BPN' was monitored and correlated to the level of enzymatic activity when suspended in isooctane. In addition, the ability of ionic detergents to stabilize subtilisin BPN' via ion pairing was evaluated. It was found that subtilisin unfolds to some degree during lyophilization, whether it is ion paired or not. Furthermore, there are structural changes observed when the enzyme is placed in isooctane, although the effects are less with ion-paired subtilisin. This higher level of retention of secondary structure results in increased enzymatic activity.

  19. Spectrophotometric determination of traces of iodide by liquid-liquid extraction of Brilliant Green-iodide ion pair

    Niazi, S.B.; Mozammil, Mohammad (Bahauddin Zakariya University, Multan (Pakistan). Department of Chemistry)


    Iodide in natural waters at the 10{sup -6} M level is determined spectrophotometrically as the Brilliant Green-iodide ion pair. Iodide is the first oxidized to iodide with hydrogen peroxide-sulphuric acid to separate it from other chemical species and extracted into carbon tetrachloride. It is then extracted back into aqueous medium by its reduction with sodium thiosulphate and stabilized as the ion pair with Brilliant Green. At pH 7 the ion pair is extracted into chloroform and the absorbance is measured at 625 nm against chloroform. A linear calibration graph is obtained over the range 5x10{sup -7}-3.5x10{sup -6} M iodide with a relative standard deviation of 0.38 % at the 2x10{sup -6} M iodide level. The apparent molar absorptivity for iodide is 3.0x10{sup 5} l mol{sup -1} cm{sup -1}. (author). 11 refs.; 4 figs.; 2 tabs.

  20. Effect of Different Concentration of MgSO4 and KH2PO4 on Biomass of Shiitake Liquid Culture%不同浓度MgSO4和KH2PO4对香菇液体培养生长量的影响

    康健; 王海华; 左斌; 吴辉群


    本文研究了MgSO4、KH2PO4二种无机物与香菇Cr-02液体发酵生长量的关系。结果证明:在27℃摇床转速为134r/min的培养条件下,MgSO4浓度0 .05%,KH2PO4浓度为0.10%,发酵96h香菇生长量最大,发酵液透光率T在630nm波长时达135.8%,其湿菌体产量32.6g/100mL,发酵液由深褐色变成黄色、粘度大、透明,菌丝体个体较大且数目较多%In this paper we study the relationship between MgSO4,KH2P O4 and biomass of shiitake.The results reveal that the biomass of shiitake is the largest after fermented for 96h on condition that the temperature is at 27℃ ,the shaker rotation speed is at 134 r/mim,the concentration of MgSO4 is 0.05 %,that of KH2PO4 is 0.01%.The transmittance of the fermentation solution is 135.8%.When the wavelengh is 630nm and the yield of wet somatic is 32.6g/100m L,the fermentation solution turns light yellow,which is transparent,the body of myc elium pellet is a bit large and the number of mycelium pellet is a bit large too .

  1. The roles of entropy and enthalpy in stabilizing ion-pairs at transition states in zeolite acid catalysis.

    Gounder, Rajamani; Iglesia, Enrique


    Acidic zeolites are indispensable catalysts in the petrochemical industry because they select reactants and their chemical pathways based on size and shape. Voids of molecular dimensions confine reactive intermediates and transition states that mediate chemical reactions, stabilizing them by van der Waals interactions. This behavior is reminiscent of the solvation effects prevalent within enzyme pockets and has analogous consequences for catalytic specificity. Voids provide the "right fit" for certain transition states, reflected in their lower free energies, thus extending the catalytic diversity of zeolites well beyond simple size discrimination. This catalytic diversity is even more remarkable because acid strength is essentially unaffected by confinement among known crystalline aluminosilicates. In this Account, we discuss factors that determine the "right fit" for a specific chemical reaction, exploring predictive criteria that extend the prevailing discourse based on size and shape. We link the structures of reactants, transition states, and confining voids to chemical reactivity and selectivity. Confinement mediates enthalpy-entropy compromises that determine the Gibbs free energies of transition states and relevant reactants; these activation free energies determine turnover rates via transition state theory. At low temperatures (400-500 K), dimethyl ether carbonylation occurs with high specificity within small eight-membered ring (8-MR) voids in FER and MOR zeolite structures, but at undetectable rates within larger voids (MFI, BEA, FAU, and SiO(2)-Al(2)O(3)). More effective van der Waals stabilization within 8-MR voids leads to lower ion-pair enthalpies but also lower entropies; taken together, carbonylation activation free energies are lower within 8-MR voids. The "right fit" is a "tight fit" at low temperatures, a consequence of how temperature appears in the defining equation for Gibbs free energy. In contrast, entropy effects dominate in high

  2. Ion-pairing HPLC methods to determine EDTA and DTPA in small molecule and biological pharmaceutical formulations$

    George Wang; Frank P. Tomasella


    Ion-pairing high-performance liquid chromatography–ultraviolet (HPLC–UV) methods were developed to determine two commonly used chelating agents, ethylenediaminetetraacetic acid (EDTA) in Abilifys (a small molecule drug with aripiprazole as the active pharmaceutical ingredient) oral solution and die-thylenetriaminepentaacetic acid (DTPA) in Yervoys (a monoclonal antibody drug with ipilimumab as the active pharmaceutical ingredient) intravenous formulation. Since the analytes, EDTA and DTPA, do not contain chromophores, transition metal ions (Cu2 þ , Fe3 þ ) which generate highly stable metallocom-plexes with the chelating agents were added into the sample preparation to enhance UV detection. The use of metallocomplexes with ion-pairing chromatography provides the ability to achieve the desired sensitivity and selectivity in the development of the method. Specifically, the sample preparation in-volving metallocomplex formation allowed sensitive UV detection. Copper was utilized for the de-termination of EDTA and iron was utilized for the determination of DTPA. In the case of EDTA, a gradient mobile phase separated the components of the formulation from the analyte. In the method for DTPA, the active drug substance, ipilimumab, was eluted in the void. In addition, the optimization of the concentration of the ion-pairing reagent was discussed as a means of enhancing the retention of the aminopolycarboxylic acids (APCAs) including EDTA and DTPA and the specificity of the method. The analytical method development was designed based on the chromatographic properties of the analytes, the nature of the sample matrix and the intended purpose of the method. Validation data were presented for the two methods. Finally, both methods were successfully utilized in determining the fate of the chelates.

  3. Scale-up potential of ion-pair high-performance liquid chromatography method to produce biologically active inositol phosphates.

    Hamada, Jamel S


    This study was undertaken to evaluate the possibility that an analytical ion-pair HPLC procedure used to determine phytic acid (IP6) and its degradation products (IP3-IP5) can be transformed to a preparative purification method. A commercial phytic acid (CPA) preparation was separated into its component fractions of IP3, IP4, IPS, and IP6 on two C18 columns (1.8 and 4.2 ml) using 51% methanol containing 0.6-1% tetrabutylammonium hydroxide as ion-pair reagent and 0-0.025 M formic acid (pH 4.3) as eluent at 1.7 and 3.0 cm/min linear velocity, respectively, and 40 degrees C. Elution was monitored at 40 degrees C by a refractive index detector. Reproducible separation of CPA into four well-resolved peaks on these columns was possible after optimizing method variables, particularly the concentration of ion-pair reagent in the injected sample (>1.5%). The same separations were obtained after CPA loads were scaled up 25 times on a steel column (15 cm x 19 mm I.D.), packed with Ethyl C2 sorbent (10 microm) and on a 25 cm x 21.2 mm I.D. C18 column, but at a reduced linear velocity to increase the resolution. Therefore, this optimization of separation not only is useful for analysis of phytic acid and its degradation products but also it provides key parameters for scale up for further fractionation and characterization.

  4. Ionic force field optimization based on single-ion and ion-pair solvation properties: going beyond standard mixing rules.

    Fyta, Maria; Netz, Roland R


    Using molecular dynamics (MD) simulations in conjunction with the SPC/E water model, we optimize ionic force-field parameters for seven different halide and alkali ions, considering a total of eight ion-pairs. Our strategy is based on simultaneous optimizing single-ion and ion-pair properties, i.e., we first fix ion-water parameters based on single-ion solvation free energies, and in a second step determine the cation-anion interaction parameters (traditionally given by mixing or combination rules) based on the Kirkwood-Buff theory without modification of the ion-water interaction parameters. In doing so, we have introduced scaling factors for the cation-anion Lennard-Jones (LJ) interaction that quantify deviations from the standard mixing rules. For the rather size-symmetric salt solutions involving bromide and chloride ions, the standard mixing rules work fine. On the other hand, for the iodide and fluoride solutions, corresponding to the largest and smallest anion considered in this work, a rescaling of the mixing rules was necessary. For iodide, the experimental activities suggest more tightly bound ion pairing than given by the standard mixing rules, which is achieved in simulations by reducing the scaling factor of the cation-anion LJ energy. For fluoride, the situation is different and the simulations show too large attraction between fluoride and cations when compared with experimental data. For NaF, the situation can be rectified by increasing the cation-anion LJ energy. For KF, it proves necessary to increase the effective cation-anion Lennard-Jones diameter. The optimization strategy outlined in this work can be easily adapted to different kinds of ions.

  5. Ion pair-reversed phase HPLC approach facilitates subcloning of PCR products and screening of recombinant colonies.

    Shaw-Bruha, C M; Lamb, K A


    The isolation of a single DNA molecule for cloning is technically difficult, and the subsequent screening of colonies for recombinant DNA clones is time consuming. Ion pair-reversed phase HPLC (IP-RP-HPLC) analysis of nucleic acids improves the resolution and isolation of PCR products to be cloned. We demonstrate that PCR products analyzed and collected using the IP-RP-HPLC approach (WAVE DNA Fragment Analysis System) can be cloned directly into a plasmid vector. In addition, we demonstrate that when IP-RP-HPLC analysis is extended to the colony screening process, the time required for these procedures is reduced.

  6. Separation of polar betalain pigments from cacti fruits of Hylocereus polyrhizus by ion-pair high-speed countercurrent chromatography.

    Wybraniec, Sławomir; Stalica, Paweł; Jerz, Gerold; Klose, Bettina; Gebers, Nadine; Winterhalter, Peter; Spórna, Aneta; Szaleniec, Maciej; Mizrahi, Yosef


    Polar betacyanin pigments together with betaxanthins from ripe cactus fruits of Hylocereus polyrhizus (Cactaceae) were fractionated by means of preparative ion-pair high-speed countercurrent chromatography (IP-HSCCC) also using the elution-extrusion (EE) approach for a complete pigment recovery. HSCCC separations were operated in the classical 'head-to-tail' mode with an aqueous mobile phase. Different CCC solvent systems were evaluated in respect of influence and effectiveness of fractionation capabilities to separate the occurring pigment profile of H. polyrhizus. For that reason, the additions of two different volatile ion-pair forming perfluorinated carboxylic acids (PFCA) were investigated. For a direct comparison, five samples of Hylocereus pigment extract were run on preparative scale (900 mg) in 1-butanol-acetonitrile-aqueous TFA 0.7% (5:1:6, v/v/v) and the modified systems tert.-butyl methyl ether-1-butanol-acetonitrile-aqueous PFCA (2:2:1:5, v/v/v/v) using 0.7% and 1.0% trifluoroacetic acid (TFA) or heptafluorobutyric acid (HFBA) in the aqueous phase, respectively. The chemical affinity to the organic stationary CCC solvent phases and in consequence the retention of these highly polar betalain pigments was significantly increased by the use of the more lipophilic fluorinated ion-pair reagent HFBA instead of TFA. The HFBA additions separated more effectively the typical cacti pigments phyllocactin and hylocerenin from betanin as well as their iso-forms. Unfortunately, similar K(D) ratios and selectivity factors alpha around 1.0-1.1 in all tested solvent systems proved that the corresponding diastereomers, 15S-type pigments cannot be resolved from the 15R-epimers (iso-forms). Surprisingly, additions of the stronger ion-pair reagent (HFBA) resulted in a partial separation of hylocerenin from phyllocactin which were not resolved in the other solvent systems. The pigments were detected by means of HPLC-DAD and HPLC-electrospray ionization-MS using also

  7. Analysis of penicillin N ring expansion activity from Streptomyces clavuligerus by ion-pair high-pressure liquid chromatography.

    JENSEN, S. E.; Westlake, D W; Wolfe, S.


    An ion-pair, reversed-phase, high-pressure liquid chromatographic method for the analysis of penicillin N ring expansion activity has been developed which allows simultaneous measurement of both substrate and product. The high-pressure liquid chromatography conditions were as follows: stationary phase, C18; flow rate, 2 ml/min; detection, 220 nm. The stationary phase was preconditioned with 4.5 mM tetrabutylammonium bromide in 0.05 M KH2PO4 (pH 4.0)-methanol (85:15, vol/vol) and then equilibr...

  8. Ab initio potential energy curves of the valence, Rydberg, and ion-pair states of iodine monochloride, ICl.

    Kalemos, Apostolos; Prosmiti, Rita


    We present for the first time a coherent ab initio study of 39 states of valence, Rydberg, and ion-pair character of the diatomic interhalogen ICl species through large scale multireference variational methods including spin-orbit effects coupled with quantitative basis sets. Various avoided crossings are responsible for a non-adiabatic behaviour creating a wonderful vista for its theoretical description. Our molecular constants are compared with all available experimental data with the aim to assist experimentalists especially in the high energy regime of up to ~95,000 cm(-1).

  9. Molecular treatment of the ion-pair formation reaction in H(1s) + H(1s) collisions

    Borondo, F.; Martin, F.; Yaez, M.


    All the available theoretical calculations of the cross section for the ion-pair formation reaction H(1s)+H(1s)..-->..H/sup +/H/sup -/(1s/sup 2/) have been performed using methods that are only valid at high collision energies. They get good agreement with the experiments for impact energies greater than 25 keV, but fail completely at smaller energies. In this work we report the cross section for this reaction at impact energies less than 10 keV, calculated in the framework of the impact-parameter approximation and using the molecular method with a common translation factor.

  10. Separation of polyprenyl phosphate oligomerhomologues by reversed-phase ion-pair high-performance liquid chromatography.

    Kozlov, Vyacheslav V; Danilov, Leonid L


    A simple and rapid method of reversed-phase ion-pair high-performance liquid chromatography (HPLC) with UV-detection on a common C(18) column in an isocratic mode with the addition of tetrabutylammonium phosphate for the separation of polyprenyl phosphate oligomerhomologues has been developed. The method was successfully applied to assay the composition of polyprenyl phosphates obtained from polyprenols isolated from mulberry (Morus alba) leaves and fir (Abies sibirica) needles (the active components of veterinary drugs Gamapren and Phosprenyl correspondingly).

  11. Ion-pair cloud-point extraction: a new method for the determination of water-soluble vitamins in plasma and urine.

    Heydari, Rouhollah; Elyasi, Najmeh S


    A novel, simple, and effective ion-pair cloud-point extraction coupled with a gradient high-performance liquid chromatography method was developed for determination of thiamine (vitamin B1 ), niacinamide (vitamin B3 ), pyridoxine (vitamin B6 ), and riboflavin (vitamin B2 ) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion-pair formation approach between these ionizable analytes and 1-heptanesulfonic acid sodium salt as an ion-pairing agent. Influential variables on the ion-pair cloud-point extraction efficiency, such as the ion-pairing agent concentration, ionic strength, pH, volume of Triton X-100, extraction temperature, and incubation time have been fully evaluated and optimized. Water-soluble vitamins were successfully extracted by 1-heptanesulfonic acid sodium salt (0.2% w/v) as ion-pairing agent with Triton X-100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r(2) > 0.9916) and precision in the concentration ranges of 1-50 μg/mL for thiamine and niacinamide, 5-100 μg/mL for pyridoxine, and 0.5-20 μg/mL for riboflavin. The recoveries were in the range of 78.0-88.0% with relative standard deviations ranging from 6.2 to 8.2%.

  12. Elucidating the structures and cooperative binding mechanism of cesium salts to the multitopic ion-pair receptor through density functional theory calculations.

    Sadhu, Biswajit; Sundararajan, Mahesh; Velmurugan, Gunasekaran; Venuvanalingam, Ponnambalam


    Designing new and innovative receptors for the selective binding of radionuclides is central to nuclear waste management processes. Recently, a new multi-topic ion-pair receptor was reported which binds a variety of cesium salts. Due to the large size of the receptor, quantum chemical calculations on the full ion-pair receptors are restricted, thus the binding mechanisms are not well understood at the molecular level. We have assessed the binding strengths of various cesium salts to the recently synthesized multi-topic ion-pair receptor molecule using density functional theory based calculations. Our calculations predict that the binding of cesium salts to the receptor predominantly occurs via the cooperative binding mechanism. Cesium and the anion synergistically assist each other to bind favorably inside the receptor. Energy decomposition analysis on the ion-pair complexes shows that the Cs salts are bound to the receptor mainly through electrostatic interactions with small contribution from covalent interactions for large ionic radius anions. Further, QTAIM analysis characterizes the importance of different inter-molecular interactions between the ions and the receptor inside the ion-pair complexes. The role of the crystallographic solvent molecule contributes significantly by ~10 kcal mol(-1) to the overall binding affinities which is quite significant. Further, unlike the recent molecular mechanics (MM) calculations, our calculated binding affinity trends for various Cs ion-pair complexes (CsF, CsCl and CsNO3) are now in excellent agreement with the experimental binding affinity trends.

  13. Nuclear Magnetic Resonance Structures of GCN4p Are Largely Conserved When Ion Pairs Are Disrupted at Acidic pH but Show a Relaxation of the Coiled Coil Superhelix.

    Kaplan, Anne R; Brady, Megan R; Maciejewski, Mark W; Kammerer, Richard A; Alexandrescu, Andrei T


    To understand the roles ion pairs play in stabilizing coiled coils, we determined nuclear magnetic resonance structures of GCN4p at three pH values. At pH 6.6, all acidic residues are fully charged; at pH 4.4, they are half-charged, and at pH 1.5, they are protonated and uncharged. The α-helix monomer and coiled coil structures of GCN4p are largely conserved, except for a loosening of the coiled coil quaternary structure with a decrease in pH. Differences going from neutral to acidic pH include (i) an unwinding of the coiled coil superhelix caused by the loss of interchain ion pair contacts, (ii) a small increase in the separation of the monomers in the dimer, (iii) a loosening of the knobs-into-holes packing motifs, and (iv) an increased separation between oppositely charged residues that participate in ion pairs at neutral pH. Chemical shifts (HN, N, C', Cα, and Cβ) of GCN4p display a seven-residue periodicity that is consistent with α-helical structure and is invariant with pH. By contrast, periodicity in hydrogen exchange rates at neutral pH is lost at acidic pH as the exchange mechanism moves into the EX1 regime. On the basis of (1)H-(15)N nuclear Overhauser effect relaxation measurements, the α-helix monomers experience only small increases in picosecond to nanosecond backbone dynamics at acidic pH. By contrast, (13)C rotating frame T1 relaxation (T1ρ) data evince an increase in picosecond to nanosecond side-chain dynamics at lower pH, particularly for residues that stabilize the coiled coil dimerization interface through ion pairs. The results on the structure and dynamics of GCNp4 over a range of pH values help rationalize why a single structure at neutral pH poorly predicts the pH dependence of the unfolding stability of the coiled coil.

  14. Spectrophotometric determination of ampicillin, dicluxacillin, flucloxacillin and amoxicillin antibiotic drugs: ion-pair formation with molybdenum and thiocyanate.

    Mohamed, G G


    A sensitive spectrophotometric method is developed for the determination of some antibiotic drugs such as ampicillin (amp), dicluxacillin (dicl), flucloxacillin (fluc) and amoxicillin (amox). The method involves the formation of ion-pairs between these drugs under investigation and inorganic complex of Mo (V) thiocyanate followed by its extraction with methylene chloride. The optimum conditions for the ion-pairs formation are established. The method permits the determination of amp, dicl, fluc and amox over a concentration range of 1.5-77.5, 3-75, 1.5-79 and 7.5-75 microg ml(-1) respectively. The sensitivity (S) is found to be 0.017, 0.061, 0.014 and 0.073 microg cm(-2) for amp, dicl, fluc and amox, respectively. The method is simple, rapid, reproducible and accurate within +/- 1%. The method is applicable for the assay of the four drugs under investigation in different dosage forms and the results are in good agreement with those obtained by the official method.

  15. Heavy Rydberg behaviour in high vibrational levels of some ion-pair states of the halogens and inter-halogens

    Donovan, Robert J., E-mail:, E-mail:; Lawley, Kenneth P., E-mail:; Ridley, Trevor, E-mail:, E-mail: [School of Chemistry, University of Edinburgh, Joseph Black Building, Edinburgh EH9 3FJ (United Kingdom)


    We report the identification of heavy Rydberg resonances in the ion-pair spectra of I{sub 2}, Cl{sub 2}, ICl, and IBr. Extensive vibrational progressions are analysed in terms of the energy dependence of the quantum defect δ(E{sub b}) rather than as Dunham expansions. This is shown to define the heavy Rydberg region, providing a more revealing fit to the data with fewer coefficients and leads just as easily to numbering data sets separated by gaps in the observed vibrational progressions. Interaction of heavy Rydberg states with electronic Rydberg states at avoided crossings on the inner wall of the ion-pair potential is shown to produce distinctive changes in the energy dependence of δ(E{sub b}), with weak and strong interactions readily distinguished. Heavy Rydberg behaviour is found to extend well below near-dissociation states, down to vibrational levels ∼18 000-20 000 cm{sup −1} below dissociation. The rapid semi-classical calculation of δ(E{sub b}) for heavy Rydberg states is emphasised and shows their absolute magnitude to be essentially the volume of phase space excluded from the vibrational motion by avoiding core-core penetration of the ions.

  16. Utility of Charge Transfer and Ion-Pair Complexation for Spectrophotometric Determination of Eletriptan Hydrobromide in Pure and Dosage Forms

    Ayman A. Gouda


    Full Text Available Three simple, sensitive, and accurate spectrophotometric methods have been developed for the determination of eletriptan hydrobromide (ELT in pure and dosage forms. The first two methods are based on charge transfer complex formation between ELT and chromogenic reagents quinalizarin (Quinz and alizarin red S (ARS producing charge transfer complexes which showed an absorption maximum at 569 and 533 nm for Quinz and ARS, respectively. The third method is based on the formation of ion-pair complex between ELT with molybdenum(V-thiocyanate inorganic complex in hydrochloric acid medium followed by extraction of the colored ion-pair with dichloromethane and measured at 470 nm. Different variables affecting the reactions were studied and optimized. Beer's law is obeyed in the concentration ranges 2.0–18, 1.0–8.0, and 2.0–32 μg mL−1 for Quinz, ARS, and Mo(V-thiocyanate, respectively. The molar absorptivity, Sandell sensitivity, detection, and quantification limits are also calculated. The correlation coefficients were ≥0.9994 with a relative standard deviation (R.S.D%. of ≤0.925. The proposed methods were successfully applied for simultaneous determination of ELT in tablets with good accuracy and precision and without interferences from common additives, and the validity is assessed by applying the standard addition technique, which is compared with those obtained using the reported method.

  17. Structural and thermodynamic consequences of burial of an artificial ion pair in the hydrophobic interior of a protein.

    Robinson, Aaron C; Castañeda, Carlos A; Schlessman, Jamie L; García-Moreno, E Bertrand


    An artificial charge pair buried in the hydrophobic core of staphylococcal nuclease was engineered by making the V23E and L36K substitutions. Buried individually, Glu-23 and Lys-36 both titrate with pKa values near 7. When buried together their pKa values appear to be normal. The ionizable moieties of the buried Glu-Lys pair are 2.6 Å apart. The interaction between them at pH 7 is worth 5 kcal/mol. Despite this strong interaction, the buried Glu-Lys pair destabilizes the protein significantly because the apparent Coulomb interaction is sufficient to offset the dehydration of only one of the two buried charges. Save for minor reorganization of dipoles and water penetration consistent with the relatively high dielectric constant reported by the buried ion pair, there is no evidence that the presence of two charges in the hydrophobic interior of the protein induces any significant structural reorganization. The successful engineering of an artificial ion pair in a highly hydrophobic environment suggests that buried Glu-Lys pairs in dehydrated environments can be charged and that it is possible to engineer charge clusters that loosely resemble catalytic sites in a scaffold protein with high thermodynamic stability, without the need for specialized structural adaptations.

  18. Ion-pair mediated transport of small model peptides in liquid phase micro extraction under acidic conditions.

    Reubsaet, J Léon E; Paulsen, Jonas V


    This paper discusses the behaviour of five small model peptides in a three phase (aqueous donor-organic-aqueous acceptor) liquid phase micro extraction system in relation to their physico-chemical properties (charge, hydrophobicity). It is proved that for all peptides transport over the organic phase is mediated by aliphatic sulphonic acids. Heptane-1-sulphonic acid gave the best overall recoveries. It appeared that peptides with hydrophobic properties (IPI) and a high number of positive charges (KYK) show good recoveries and are enriched in the acceptor phase. Variation in the pH (1.6-4.4) of the donor phase shows that there are peptide-dependent optimal pH-values for their recovery. Increasing pH in the acceptor phase shows that in most cases the recovery decreases due to decreased ion-pair mediated membrane transport. For KYK the partition between the organic phase and the aqueous acceptor-phase is also driven by the solubility in the aqueous acceptor phase. Increase of the ion strength of the acceptor phase did not affect the recovery of the peptides. Except for KYK, which showed decreased recovery when the ion strength increased. Another finding is that delocalisation of positive charge causes bad recovery, probably due to incomplete ion-pair-peptide complex formation.

  19. Ion pairing with linoleic acid simultaneously enhances encapsulation efficiency and antibacterial activity of vancomycin in solid lipid nanoparticles.

    Kalhapure, Rahul S; Mocktar, Chunderika; Sikwal, Dhiraj R; Sonawane, Sandeep J; Kathiravan, Muthu K; Skelton, Adam; Govender, Thirumala


    Ion pairing of a fatty acid with an antibiotic may be an effective strategy for formulation optimization of a nanoantibiotic system. The aim of this study was therefore to explore the potential of linoleic acid (LA) as an ion pairing agent to simultaneously enhance encapsulation efficiency and antibacterial activity of triethylamine neutralized vancomycin (VCM) in solid lipid nanoparticles (SLNs). The prepared VCM-LA2 conjugate was characterized by Fourier transform-infrared (FT-IR) spectroscopy, logP and binding energy calculations. The shifts in the FT-IR frequencies of COOH, NH2 and CO functionalities, an increase in logP value (1.37) and a lower interaction energy between LA and VCM (-125.54 kcal/mol) confirmed the formation of the conjugate. SLNs were prepared by a hot homogenization and ultrasonication method, and characterized for size, polydispersity index (PI), zeta potential (ZP), entrapment efficiency (%EE), surface morphology and physical stability. In vitro antibacterial activity studies against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) were conducted. Size, PI and ZP for VCM-LA2_SLNs were 102.7±1.01, 0.225±0.02 and -38.8±2.1 (mV) respectively. SLNs were also stable at 4 °C for 3 months. %EE for VCM-HCl_SLNs and VCM-LA2_SLNs were 16.81±3.64 and 70.73±5.96 respectively, indicating a significant improvement in encapsulation of the drug through ion pairing with LA. Transmission electron microscopy images showed spherical nanoparticles with sizes in the range of 95-100 nm. After 36 h, VCM-HCl showed no activity against MRSA. However, the minimum inhibitory concentration for VCM-HCl_SLNs and VCM-LA2_SLNs were 250 and 31.25 μg/ml respectively against S. aureus, while against MRSA it was 500 and 15.62 μg/ml respectively. This confirms the enhanced antibacterial activity of VCM-LA2_SLNs over VCM-HCl_SLNs. These findings therefore suggest that VCM-LA2_SLNs is a promising nanoantibiotic system for effective treatment against both

  20. Investigation on the ion pair amphiphiles and their in vitro release of amantadine drug based on PLGA–PEG–PLGA gel

    Yang, Xiaoxia, E-mail:; Ji, Xiaoqing; Shi, Chunhuan; Liu, Jing [Shandong University, School of Pharmaceutical Science and Center for Pharmaceutical Research & Drug Delivery Systems (China); Wang, Haiyang [Institute of Materia Medica Shandong Academy of Medical Sciences, Shandong Taitian Newdrug Discovery Co.Ltd (China); Luan, Yuxia, E-mail: [Shandong University, School of Pharmaceutical Science and Center for Pharmaceutical Research & Drug Delivery Systems (China)


    The amantadine drug and oleic acid surfactant are used to form amantadine-based ion pair amphiphiles based on proton transfer reaction between the drug and the surfactant molecules. The ion pair amphiphiles are characterized by {sup 1}H-nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray diffraction. Self-assembly properties of amantadine-based ion pair amphiphiles are studied by surface tension determination, transmission electron microscopy, zeta potential, and dynamic light scattering. The aggregation behavior studies indicate that the as-prepared ion pair amphiphiles can self-assemble into vesicles with the size of 200–300 nm in aqueous solution. The drug release results show that the amantadine release rate could be well controlled by incorporating the amantadine-based ion pair vesicles in poly (lactic-co-glycolic acid)-poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PLGA–PEG–PLGA) copolymer hydrogel. The drug release from the AT–OA vesicle-loaded PLGA–PEG–PLGA hydrogel is significantly inhibited in comparison with the AT-loaded PLGA–PEG–PLGA hydrogel. The present work thus demonstrates that the vesicle-loaded hydrogel is a good candidate for the drug delivery system with long-term controlled drug release behavior.

  1. [Separation of zoledronic acid and its related substances by ion-pair reversed-phase high performance liquid chromatography].

    Zhang, Xiaoqing; Jiang, Ye; Xu, Zhiru


    A rapid and simple ion-pair reversed-phase high performance liquid chromatographic method (HPLC) has been established for the routine analysis of zoledronic acid and its related substances. The chromatographic conditions were optimized based on the satisfactory separation of zoledronic acid from imidazol-1-ylacetic acid, their retention times and peak shape. The excellent separation of zoledronic acid from its related substances, including the remaining imidazol-1-ylacetic acid used in the synthesis of zoledronic acid and other impurities of oxidation and decomposition, was achieved within 9 min on a Hypersil C8 column with UV detection at 220 nm. The mobile phase was a mixture of methanol (20%) and 5 mmo/L phosphate buffer (80%) that contains 6 mmol/L tetrabutylammonium bromide. The resolution factor of zoledronic acid from its adjacent peak was more than 2.5. This is a simple and rapid method for the routine assay of zoledronic acid.

  2. Determination of ellagic acid in oak leaves and in sheep ruminal fluid by ion-pair RP-HPLC.

    del Moral, P García; Arín, M J; Resines, J A; Díez, M T


    An isocratic ion-pair high-performance liquid chromatography (IP-RP-HPLC) method with UV detection was developed to identify and quantify ellagic acid (EA). This phenolic compound is widely distributed in the plants and is often present in the diet of ruminants. The method was validated and validation parameters were: linearity range 5-100 mg/L; correlation coefficient, 0.9995; mean recoveries (99.94 and 101.07%) and detection limit 1.4 mg/L. Method was applied for the determination of ellagic acid in oak leaves and in ruminal fluid from to a vitro ruminal system. The proposed method proved to be rapid and accurate and can be successfully used in ruminant nutrition studies.

  3. Novel cationic surfactant ion pair based solid phase microextraction fiber for nano-level analysis of BTEX.

    Hosseinzadeh, Reza; Tahmasebi, Raheleh; Farhadi, Khalil; Moosavi-Movahedi, Ali Akbar; Jouyban, Abolghasem; Badraghi, Jalil


    Ion pair of cationic surfactant (cetytrimethylammonium bromide) and tungestosilicic acid incorporated in PVC matrix, was used for coating a piece of copper wire as a new high sensitive SPME fiber in extraction and determination of BTEX compounds from the headspace of water samples prior to GC/FID analysis. Under optimum extraction conditions, limits of detection for benzene, toluene, ethylbenzene, p-xylene, m-xylene and o-xylene were found to be 1.18, 5.61, 0.87, 0.29, 0.22 and 0.33 ng L(-1) respectively. Low detection limits, wide linear dynamic ranges, good reproducibility (RSD% 1.48-4.27), high fiber capacity and high mechanical durability are some of the most important advantages of the new fiber.

  4. Ion-pair formation in aqueous strontium chloride and strontium hydroxide solutions under hydrothermal conditions by AC conductivity measurements.

    Arcis, H; Zimmerman, G H; Tremaine, P R


    Frequency-dependent electrical conductivities of solutions of aqueous strontium hydroxide and strontium chloride have been measured from T = 295 K to T = 625 K at p = 20 MPa, over a very wide range of ionic strength (3 × 10(-5) to 0.2 mol kg(-1)), using a high-precision flow AC conductivity instrument. Experimental values for the concentration-dependent equivalent conductivity, Λ, of the two electrolytes were fitted with the Turq-Blum-Bernard-Kunz ("TBBK") ionic conductivity model, to determine ionic association constants, K(A,m). The TBBK fits yielded statistically significant formation constants for the species SrOH(+) and SrCl(+) at all temperatures, and for Sr(OH)2(0) and SrCl2(0) at temperatures above 446 K. The first and second stepwise association constants for the ion pairs followed the order K(A1)(SrOH(+)) > K(A1)(SrCl(+)) > K(A2)[Sr(OH)2(0)] > K(A2)[SrCl2(0)], consistent with long-range solvent polarization effects associated with the lower static dielectric constant and high compressibility of water at elevated temperatures. The stepwise association constants to form SrCl(+) agree with previously reported values for CaCl(+) to within the combined experimental error at high temperatures and, at temperatures below ∼375 K, the values of log10 KA1 for strontium are lower than those for calcium by up to ∼0.3-0.4 units. The association constants for the species SrOH(+) and Sr(OH)2(0) are the first accurate values to be reported for hydroxide ion pairs with any divalent cation under these conditions.

  5. Ion-Pair Halogen Bonds in 2-Halo-Functionalized Imidazolium Chloride Receptors: Substituent and Solvent Effects.

    Nunes, Rafael; Costa, Paulo J


    The interaction of 2-halo-functionalized imidazolium derivatives (n-X(+) ; X=Cl, Br, I) with a chloride anion through ion-pair halogen bonds (n-X⋅Cl) was studied by means of DFT and ab initio calculations. A method benchmark was performed on 2-bromo-1H-imidazol-3-ium in association with chloride (1-Br⋅Cl); MP2 yielded the best results when compared with CCSD(T) calculations. The interaction energies (ΔE) in the gas phase are high and, although the electrostatic interaction is strong owing to the ion-pair nature of the system, large X⋅⋅⋅Cl(-) Wiberg bond orders and contributions from charge transfer (nCl- →σ*C-X) are obtained. These values drop considerably in chloroform and water; this shows that solvent plays a role in modulating the interaction and that gas-phase calculations are particularly unrealistic for experimental applications. The introduction of electron-withdrawing groups in the 4,5-positions of the imidazolium (e.g., -NO2 , -F) increases the halogen-bond strength in both the gas phase and solvent, including water. The effect of the substituents on the 1,3-positions (N-H groups) also depends on the solvent. The variation of ΔE can be predicted through a two-parameter linear regression that optimizes the weights of charge-transfer and electrostatic interactions, which are different in vacuum and in solvent (chloroform and water). These results could be used in the rational design of efficient chloride receptors based on halogen bonds that work in solution, in particular, in an aqueous environment.

  6. Using beryllium bonds to change halogen bonds from traditional to chlorine-shared to ion-pair bonds.

    Alkorta, Ibon; Elguero, José; Mó, Otilia; Yáñez, Manuel; Del Bene, Janet E


    Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate the structures, binding energies, and bonding characteristics of binary complexes HFBe:FCl, R2Be:FCl, and FCl:N-base, and of ternary complexes HFBe:FCl:N-base and R2Be:FCl:N-base for R = H, F, Cl; N-base = NH3, NHCH2, NCH. Dramatic synergistic cooperative effects have been found between the Be···F beryllium bonds and the Cl···N halogen bonds in ternary complexes. The Cl···N traditional halogen bonds and the Be···F beryllium bonds in binary complexes become significantly stronger in ternary complexes, while the F-Cl bond weakens. Charge-transfer from F to the empty p(σ) orbital of Be leads to a bending of the XYBe molecule and a change in the hybridization of Be, which in the limit becomes sp(2). As a function of the intrinsic basicity of the nitrogen base and the intrinsic acidity of the Be derivative, the halogen-bond type evolves from traditional to chlorine-shared to ion-pair bonds. The mechanism by which an ion-pair complex is formed is similar to that involved in the dissociative proton attachment process. EOM-CCSD spin-spin coupling constants (1X)J(Cl-N) across the halogen bond in these complexes also provide evidence of the same evolution of the halogen-bond type.

  7. Solution structure investigation of Ru(II) complex ion pairs: quantitative NOE measurements and determination of average interionic distances.

    Zuccaccia, C; Bellachioma, G; Cardaci, G; Macchioni, A


    The structure of the Ru(II) ion pairs trans-[Ru(COMe)[(pz(2))CH(2)](CO)(PMe(3))(2)]X (X(-) = BPh(4)(-), 1a; BPh(3)Me(-), 1b; BPh(3)(n-Bu)(-), 1c; BPh(3)(n-Hex)(-), 1d; B(3, 5-(CF(3))(2)(C(6)H(3)))(4)(-), 1e; PF(6)(-), 1f; and BF(4)(-), 1g; pz = pyrazol-1-yl-ring) was investigated in solution from both a qualitative (chloroform-d, methylene chloride-d(2), nithromethane-d(3)) and quantitative (methylene chloride-d(2)) point of view by performing 1D- and 2D-NOE NMR experiments. In particular, the relative anion-cation localization (interionic structure) was qualitatively determined by (1)H-NOESY and (19)F, (1)H-HOESY (heteronuclear Overhauser effect spectroscopy) NMR experiments. The counteranion locates close to the peripheral protons of the bispyrazolyl ligand independent of its nature and that of the solvent. In complexes 1c and 1d bearing unsymmetrical counteranions, the aliphatic chain points away from the metal center as indicated by the absence of NOE between the terminal Me group and any cationic protons. An estimation of the average interionic distances in solution was obtained by the quantification of the NOE build-up versus the mixing time under the assumption that the interionic and intramolecular correlation times (tau(c)) are the same. Such an assumption was checked by the experimental measurements of tau(c) from both the dipolar contribution to the carbon-13 longitudinal relaxation time T(DD-1)and the comparison of the intramolecular and interionic cross relaxation rate constant (sigma) dependence on the temperature. Both the methodologies indicate that anion and cation have comparable tau(c) values. The determined correlation time values were compared with those obtained for the neutral trans-[Ru(COMe)[(pz(2))BH(2)](CO)(PMe(3))(2)] complex (2), isosteric with the cation of 1. They were significantly shorter (approximately 3.8 times), indicating that the main contribution to dipolar relaxation processes comes from the overall ion pair rotation. As a

  8. The coupling between stability and ion pair formation in magnesium electrolytes from first-principles quantum mechanics and classical molecular dynamics.

    Rajput, Nav Nidhi; Qu, Xiaohui; Sa, Niya; Burrell, Anthony K; Persson, Kristin A


    In this work we uncover a novel effect between concentration dependent ion pair formation and anion stability at reducing potentials, e.g., at the metal anode. Through comprehensive calculations using both first-principles as well as well-benchmarked classical molecular dynamics over a matrix of electrolytes, covering solvents and salt anions with a broad range in chemistry, we elucidate systematic correlations between molecular level interactions and composite electrolyte properties, such as electrochemical stability, solvation structure, and dynamics. We find that Mg electrolytes are highly prone to ion pair formation, even at modest concentrations, for a wide range of solvents with different dielectric constants, which have implications for dynamics as well as charge transfer. Specifically, we observe that, at Mg metal potentials, the ion pair undergoes partial reduction at the Mg cation center (Mg(2+) → Mg(+)), which competes with the charge transfer mechanism and can activate the anion to render it susceptible to decomposition. Specifically, TFSI(-) exhibits a significant bond weakening while paired with the transient, partially reduced Mg(+). In contrast, BH4(-) and BF4(-) are shown to be chemically stable in a reduced ion pair configuration. Furthermore, we observe that higher order glymes as well as DMSO improve the solubility of Mg salts, but only the longer glyme chains reduce the dynamics of the ions in solution. This information provides critical design metrics for future electrolytes as it elucidates a close connection between bulk solvation and cathodic stability as well as the dynamics of the salt.

  9. Analysis of nucleic acids by capillary ion-pair reversed-phase HPLC coupled to negative-ion electrospray ionization mass spectrometry.

    Huber, C G; Krajete, A


    Ion-pair reversed-phase high-performance liquid chromatography was successfully coupled to negative-ion electrospray ionization mass spectrometry by using 60 × 0.20 mm i.d. capillary columns packed with 2.3-μm micropellicular, octadecylated poly(styrene/divinylbenzene) particles as stationary phase and gradients of acetonitrile in 50 mM aqueous triethylammonium bicarbonate as mobile phase. Systematic variation of the eluent composition, such as concentration of ion-pair reagent, anion in the ion-pair reagent, solution pH, and acetonitrile concentration led to the conclusion that most parameters have opposite effects on chromatographic and mass spectrometric performances. The use of acetonitrile as sheath liquid enabled the rapid and highly efficient separation and detection of phosphorylated and nonphosphorylated oligonucleotides ranging in size from 8 to 40 nucleotides. High-quality full-scan mass spectra showing little cation adduction were acquired from which the molecular masses of the separated oligonucleotides were calculated with an accuracy of 0.011%. With calibration curves being linear over at least 2 orders of magnitude, the lower limits of detection for a oligodeoxythymidine 16-mer were 104 fmol with full scan and 710 amol with selected-ion-monitoring data acquisition. The potential of ion-pair reversed-phase high-performance liquid chromatography-electrospray ionization mass spectrometry was demonstrated for mixed-sequence oligomers by the characterization of a reaction mixture from solid-phase synthesis of a 40-mer oligonucleotide.

  10. Theoretical Treatment of Degenerate Electron Exchange and Dimerization in Spin Dynamics of Radical Ion Pairs as Observed by Magnetic Field Effects

    Ivanov, K.L.; Stass, D.V.; Kalneus, E.V.; Kaptein, R.; Lukzen, N.K.


    In this work we have compared manifestations of degenerate electron exchange (DEE) and dimerization reactions in MARY (magnetically affected reaction yield) spectroscopy and time-resolved magnetic field effects (TR-MFE) of radical ion pairs (RIPs). It is shown that dimerization results in phase and

  11. Metal-free reduction of the greenhouse gas sulfur hexafluoride, formation of SF5 containing ion pairs and the application in fluorinations

    Rueping, Magnus


    A protocol for the fast and selective two-electron reduction of the potent greenhouse gas sulfur hexafluoride (SF6) by organic electron donors at ambient temperature has been developed. The reaction yields solid ion pairs consisting of donor dications and SF5-anions which can be effectively used in fluorination reactions.

  12. Origin of Enhanced Reactivity of a Microsolvated Nucleophile in Ion Pair SN2 Reactions: The Cases of Sodium p-Nitrophenoxide with Halomethanes in Acetone.

    Li, Qiang-Gen; Xu, Ke; Ren, Yi


    In a kinetic experiment on the SN2 reaction of sodium p-nitrophenoxide with iodomethane in acetone-water mixed solvent, Humeres et al. (J. Org. Chem. 2001, 66, 1163) found that the reaction depends strongly on the medium, and the fastest rate constant was observed in pure acetone. The present work tries to explore why acetone can enhance the reactivity of the title reactions. Accordingly, we make a mechanistic study on the reactions of sodium p-nitrophenoxide with halomethanes (CH3X, X = Cl, Br, I) in acetone by using a supramolecular/continuum model at the PCM-MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) level, in which the ion pair nucleophile is microsolvated by one to three acetone molecules. We compared the reactivity of the microsolvated ion pair nucleophiles with solvent-free ion pair and anionic ones. Our results clearly reveal that the microsolvated ion pair nucleophile is favorable for the SN2 reactions; meanwhile, the origin of the enhanced reactivity induced by microsolvation of the nucleophile is discussed in terms of the geometries of transition state (TS) structures and activation strain model, suggesting that lower deformation energies and stronger interaction energies between the deformed reactants in the TS lead to the lower overall reaction barriers for the SN2 reaction of microsolvated sodium p-nitrophenoxide toward halomethanes in acetone.

  13. Assessing the Interplay between the Physicochemical Parameters of Ion-Pairing Reagents and the Analyte Sequence on the Electrospray Desorption Process for Oligonucleotides

    Basiri, Babak; Murph, Mandi M.; Bartlett, Michael G.


    Alkylamines are widely used as ion-pairing agents during LC-MS of oligonucleotides. In addition to a better chromatographic separation, they also assist with the desorption of oligonucleotide ions into the gas phase, cause charge state reduction, and decrease cation adduction. However, the choice of such ion-pairing agents has considerable influence on the MS signal intensity of oligonucleotides as they can also cause significant ion suppression. Interestingly, optimal ion-pairing agents should be selected on a case by case basis as their choice is strongly influenced by the sequence of the oligonucleotide under investigation. Despite imposing major practical difficulties to analytical method development, such a highly variable system that responds very strongly to the nuances of the electrospray composition provides an excellent opportunity for a fundamental study of the electrospray ionization process. Our investigations using this system quantitatively revealed the major factors that influenced the ESI ionization efficiency of oligonucleotides. Parameters such as boiling point, proton affinity, partition coefficient, water solubility, and Henry's law constants for the ion-pairing reagents and the hydrophobic thymine content of the oligonucleotides were found to be the most significant contributors. Identification of these parameters also allowed for the development of a statistical predictive algorithm that can assist with the choice of an optimum IP agent for each particular oligonucleotide sequence. We believe that research in the field of oligonucleotide bioanalysis will significantly benefit from this algorithm (included in Supplementary Material) as it advocates for the use of lesser-known but more suitable ion-pair alternatives to TEA for many oligonucleotide sequences.

  14. Rapid separation of desloratadine and related compounds in solid pharmaceutical formulation using gradient ion-pair chromatography.

    Zheng, Jinjian; Rustum, Abu M


    We reported the development of an ion-pair chromatographic method to separate desloratadine and all known related compounds in Clarinex Tablets, which use desloratadine as active pharmaceutical ingredient (API). For the first time, baseline separation for desloratadine and all known related compounds was achieved by utilizing a YMC-Pack Pro C(18) column (150 mm x 4.6 mm I.D., 3 microm particle size, 120A pore size) and a gradient elution method. The mobile phase A contains 3 mM sodium dodecylsulfate (SDS), 15 mM sodium citrate buffer at pH 6.2, and 40 mM sodium sulfate, while the mobile phase B is acetonitrile. Chromsword, an artificial intelligence method development tool, was used to optimize several key chromatographic parameters simultaneously including buffer pH/solvent strength, and temperature/gradient profile. The resolution of desloratadine and desloratadine 3,4-dehydropiperidine derivative, one of the critical pairs was improved by adding 40 mM sodium sulfate. Ultraviolet detection at 267 nm was used to achieve the detection for desloratadine and all compounds. This method has been successfully validated according to ICH guidelines in terms of linearity, accuracy, quantitation limit/detection limit, precision, specificity and robustness. It could be used as a stability indicating method for desloratadine drug substances or drug products that use desloratadine as active pharmaceutical ingredient.

  15. Determination of Fluorescent Whitening Agents in Paper Materials by Ion-Pair Reversed-Phase High-Performance Liquid Chromatography

    Kim, Jeong Soo; Kim, Keon [Korea Univ., Seoul (Korea, Republic of); Kim, Do Hwan [Daegu Univ., Gyeongsan (Korea, Republic of)


    A simple method was developed for the analysis of seven stilbene-type fluorescent whitening agents (FWAs) in paper materials by ion-pair reversed-phase high-performance liquid chromatography with fluorescence detection. These stilbene-type FWAs included two disulfonate, two tetrasulfonate, and three hexasulfonate compounds. After optimization of chromatographic conditions, the FWAs were satisfactorily separated using a reversed-phase column (RP-18) with the following isocratic mobile phase: methanol-water (60:40) containing 17.5 mM TBABr and 10 mM citrate buffer (pH = 7.0). The calibration plot was linear in the range from 5 to 500 ng/mL for two disulfo-FWAs and from 1 to 500 ng/mL for the other five FWAs. Precision levels of the calibration curve as indicated by RSD of response factors were 1.2 and 8.1%. Limits of quantitation (LOQ) ranged from 1.2 to 11 ng/mL.

  16. Temperature Dependence of the Stability of Ion Pair Interactions, and its Implications on the Thermostability of Proteins from Thermophiles



    An understanding of the determinants of the thermal stability of thermostable proteins is expected to enable design of enzymes that can be employed in industrial biocatalytic processes carried out at high temperatures. A major factor that has been proposed to stabilize thermostable proteins is the high occurrenceof salt bridges. The current study employs free energy calculations to elucidate the thermodynamics of the formation of salt bridge interactions and the temperature dependence, using acetate and methylguanidium ionsas model systems. Three different orientations of the methylguanidinium approaching the carboxylate grouphave been considered for obtaining the free energy profiles. The association of the two ions becomes more favorable with an increase in temperature. The desolvation penalty corresponding to the association of the ionpair is the lowest at high temperatures. The occurrence of bridging water molecules between the ions ensures that the ions are not fully desolvated, and this could provide an explanation for the existence of internal watermolecules in thermostable proteins reported recently. The findings provide a detailed picture of the interactions that make ion pair association at high temperatures a favorable process, and reaffirm the importance of saltbridges in the design of thermostable proteins.

  17. Determination of lincomycin residue in salmon tissues by ion-pair reversed-phase liquid chromatography with electrochemical detection

    Luo, Wenhong; Hansen, E.B. Jr.; Thompson, H.C. Jr. [National Center for Toxicological Research, Jefferson, AR (United States)] [and others


    A method is described for detecting and quantitating lincomycin residue in salmon muscle and skin tissues by ion-pair reversed-phase chromatography (LC) with electrochemical detection at +0.9 V. Lincomycin was extracted from tissues by homogenizing with 0.01M KH{sub 2}PO{sub 4} buffer (pH 4.5) and centrifuging the mixture. Water-soluble proteins were precipitated by adding sodium tungstate and sulfuric acid and removed by centrifugation. The buffer extract was then passed through a C{sub 18} solid-phase extraction cartridge. Lincomycin was eluted with 50% acetonitrile in water, and the eluate containing lincomycin was extracted with ethyl acetate. After the solvent had evaporated, the residue was redissolved in mobile phase and analyzed by LC. The method had a limit of detection of 7 ng/g lincomycin for salmon muscle and 24 ng/g for salmon skin. Average recoveries of lincomycin spiked at 50, 100, and 200 ng/g were {ge}85% for salmon muscle and {le}80% for salmon skin. 12 refs., 3 figs., 4 tabs.

  18. Spectrophotometric study of the charge-transfer and ion-pair complexation of methamphetamine with some acceptors

    Shahdousti, Parvin; Aghamohammadi, Mohammad; Alizadeh, Naader


    The charge-transfer (CT) complexes of methamphetamine (MPA) as a n-donor with several acceptors including bromocresolgreen (BCG), bromocresolpurple (BCP), chlorophenolred (CPR), picric acid (PIC), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been studied spectrophotometrically in chloroform solutions in order to obtain some information about their stoichiometry and stability of complexation. The oscillator strengths, transition dipole moments and resonance energy of the complex in the ground state for all complexes have been calculated. Vertical ionization potential of MPA and electron affinity of acceptors were determined by ab initio calculation. The acceptors were also used to utilize a simple and sensitive extraction-spectrophotometric method for the determination of MPA. The method is based on the formation of 1:1 ion-pair association complexes of MPA with BCG, BCP and PIC in chloroform medium. Beer's plots were obeyed in a general concentration range of 0.24-22 μg ml -1 for the investigated drug with different acceptors. The proposed methods were applied successfully for the determination of MAP in pure and abuse drug with good accuracy and precision.

  19. Colorimetric and atomic absorption spectrometric determination of mucolytic drug ambroxol through ion-pair formation with iron and thiocyanate.

    Levent, Abdulkadir; Sentürk, Zühre


    Colorimetric and atomic absorption spectrometric methods have been developed for the determination of mucolytic drug Ambroxol. These procedures depend upon the reaction of iron(III) metal ion with the drug in the presence of thiocyanate ion to form stable ion-pair complex which extractable chloroform. The red-coloured complex was determined either colorimetrically at 510 nm or by indirect atomic absorption spectrometry (AAS) via the determination of the iron content in the formed complex. The optimum experimental conditions for pH, concentrations of Fe(3+) and SCN(-), shaking time, phase ratio, and the number of extractions were determined. Under the proposed conditions, linearity was obeyed in the concentration ranges 4.1x10(-6) - 5.7x10(-5) M (1.7-23.6 µg mL(-1)) using both methods, with detection limits of 4.6x10(-7) M (0.19 µg mL(-1)) for colorimetry and 1.1x10(-6) M (0.46 µg mL(-1)) for AAS. The proposed methods were applied for the determination of Ambroxol in tablet dosage forms. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection.

  20. Spectrophotometric determination of benzydamine HCl, levamisole HCl and mebeverine HCl through ion-pair complex formation with methyl orange

    El-Didamony, Akram M.


    A simple, rapid and sensitive spectrophotometric method has been proposed for the assay of benzydamine HCl (BENZ), levamisole HCl (LEV) and mebeverine HCl (MBV) in bulk and pharmaceutical formulations. The method based on the reaction of the selected drugs with methyl orange (MO) in buffered aqueous solution at pH 3.6. The formed yellow ion-pair complexes were extracted with dichloromethane and measured quantitatively with maximum absorption at 422 nm. The analytical parameters and their effects on the reported systems are investigated. The extracts are intensely colored and very stable at room temperature. The calibration graphs were linear over the concentration range of 2-10 μg ml -1 for BENZ, 6-24 μg ml -1 for LEV and 4-14 μg ml -1 for MBV. The stoichiometry of the reaction was found to be 1:1 in all cases and the conditional stability constant ( Kf) of the complexes have been calculated. The proposed method was successfully extended to pharmaceutical preparations-tablets. Excipients used as additive in commercial formulations did not interfere in the analysis. The proposed method can be recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical technique are of great importance.

  1. Determination of UV active inorganic anions in potable and high salinity water by ion pair reversed phase liquid chromatography.

    Sadiq Khan, Sadaf; Riaz, M


    Reversed phase column was dynamically modified into anion exchange column using various types of tetraalkylammonium salts as ion pair reagents (IPRs) for the separation and quantification of toxic anions such as nitrite, bromate, bromide and nitrate in potable and high salinity water. Various chromatographic parameters such as types and concentration of IPRs, concentration of organic modifier, phosphate buffer and mobile phase pH were optimized for the base-line separation of anions. The lowest detection limits (LDLs) were 0.2 for nitrate and nitrite, 0.6 µg ml(-1)for bromate and bromide respectively for potable water samples. NaCl and Na₂SO₄ were incorporated in the mobile phase for the analysis of high salinity water samples to minimize matrix interferences. This has resulted in change in elution order of anions, better tolerance of matrix anions such as chloride and sulphate. The developed method was successfully utilized for analysis of anions in potable, high salinity and sea water samples.

  2. Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation

    Ragab, Gamal H.; Amin, Alaa S.


    Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at λmax 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 μg ml -1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15±1.15, 99.30±1.40, 99.60±1.50, and 99.00±1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

  3. Direct Conversion of Wheat Straw into Electricity with a Biomass Flow Fuel Cell Mediated by Two Redox Ion Pairs.

    Gong, Jian; Liu, Wei; Du, Xu; Liu, Congmin; Zhang, Zhe; Sun, Feifei; Yang, Le; Xu, Dong; Guo, Hua; Deng, Yulin


    In this paper, a biomass flow fuel cell to directly convert wheat straw to electricity at low temperature (80-90 °C) and atmospheric pressure is presented. Two redox ion pairs, Fe(3+) /Fe(2+) and VO2(+) /VO(2+) , acting as redox catalysts and charge carriers, were used in the anode and cathode flow tanks, respectively. The wheat straw was first oxidized by Fe(3+) in the anode tank at approximately 100 °C. The reduced Fe(2+) in the anode was used to construct a fuel cell with VO2(+) in the cathode. The VO2(+) ions were reduced to VO(2+) and regenerated to VO2(+) by oxygen oxidation. The wheat straw flow fuel cell showed a power output of 100 mW cm(-2) . Mediated with liquid Fe(3+) carriers, the solid powder of wheat straw could be gradually degraded into low-molecular-weight organic molecules and even oxidized to CO2 at the anode without using noble-metal catalysts. The overpotential for the electrodes of the flow fuel cell was examined and the energy cost was estimated.

  4. Ion-pair assisted extraction followed by (1)H NMR determination of biogenic amines in food and biological matrices.

    Chatzimitakos, T; Exarchou, V; Ordoudi, S A; Fiamegos, Y; Stalikas, C


    A selective method for the extraction and determination of six biogenic amines (BAs) by NMR is presented. Briefly, BAs are extracted into an organic solvent via the use of an ion pairing agent, followed by a back extraction in D2O in order to acquire the (1)H NMR spectra. The method is studied with respect to the critical experimental parameters and is successfully applied to selected food substrates (dark chocolate, banana, gouda cheese) and biological samples (urine and blood plasma) signifying its potential as an alternative tool for BAs determination. Accurate and precise results are consistently achieved with all matrixes studied. The calculated limits of detection and limits of quantitation were found to be in the ranges 0.05-0.13μg/mL and 0.14-0.38μg/mL, respectively, for biological samples while for food samples they were in the ranges 2.25-6.25μg/g and 6.75-18.7μg/g, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. DNA association-enhanced physical stability of catanionic vesicles composed of ion pair amphiphile with double-chain cationic surfactant.

    Lee, Jung; Chang, Chien-Hsiang


    Physical stability control of vesicle/DNA complexes is a key issue for the development of catanionic vesicles composed of ion pair amphiphile (IPA) as DNA carriers. In this work, physical stability characteristics of the complexes of DNA with positively charged catanionic vesicles composed of an IPA and a double-chain cationic surfactant, dihexadecyldimethylammonium bromide (DHDAB), were explored. It was found that in water, the mixed IPA/DHDAB catanionic vesicles became stable when the mole fraction of DHDAB (xDHDAB) was increased up to 0.5. The improved physical stability of the vesicles with a high xDHDAB could be related to the enhanced electrostatic interaction between the vesicles. When the catanionic vesicles interacted with DNA, excellent physical stability was detected for the vesicle/DNA complexes especially with a high xDHDAB. However, this could not be fully explained by the electrostatic interaction effect, and the role of molecular packing within the vesicular bilayers was apparently important. The corresponding Langmuir monolayer study demonstrated that the molecular packing of mixed IPA/DHDAB layers became ordered with DNA association due to inhibited desorption of the positively charged moiety of the IPA. Moreover, the DNA association-induced improvement in the molecular packing of the mixed IPA/DHDAB layers became pronounced with increased xDHDAB. The results imply that one can fabricate catanionic vesicle/DNA complexes with excellent physical stability through the improved molecular packing in the IPA vesicular bilayers with DHDAB addition and DNA association.

  6. Spectrofluorometric determination and chemical speciation of trace concentrations of tungsten species in water using the ion pairing reagent procaine hydrochloride.

    El-Shahawi, M S; Al Khateeb, L A


    A highly selective and low cost extractive spectrofluorimetric method was developed for determination of trace concentrations of tungsten (VI) in water. The method was based upon solvent extraction of the developed ion associate [(PQH(+))(2)·WO(4)(2-)] of the fluorescent ion-pairing reagent [2-(diethylamino)ethyl 4 aminobenzoate] hydrochloride namely procaine hydrochloride, PQH(+)·Cl(-) and tungstate (WO(4)(2-)) in aqueous solution of pH 6-7 followed by measuring the resulting fluorescence enhancement in n-hexane at λ(ex/em)=270/320nm. The fluorescence intensity of PQH(+)·Cl(-) increased linearly on increasing tungstate concentration in the range 25-250μgL(-1). The limits of detection (LOD) and quantification (LOQ) of tungsten (VI) were found 7.51 and 24.75μgL(-1), respectively. Chemical composition of the developed ion associate and the molar absorptivity at 270nm were found to be [(PQH(+))(2)·WO(4)(2-)] and 2.7×10(4)Lmol(-1)cm(-1), respectively. Other oxidation states (III, IV, V) of tungsten species could also be determined after oxidation with H(2)O(2) in aqueous solution to tungsten (VI). The method was applied for analysis of tungsten in certified reference material (IAEA Soil-7) and wastewater samples. The results were compared successfully (>95%) with the data of inductively coupled plasma-mass spectrometry (ICP-MS).

  7. An automated method for the analysis of phenolic acids in plasma based on ion-pairing micro-extraction coupled on-line to gas chromatography/mass spectrometry with in-liner derivatisation

    Peters, S.; Kaal, E.; Horsting, I.; Janssen, H.-G.


    A new method is presented for the analysis of phenolic acids in plasma based on ion-pairing ‘Micro-extraction in packed sorbent’ (MEPS) coupled on-line to in-liner derivatisation-gas chromatography-mass spectrometry (GC-MS). The ion-pairing reagent served a dual purpose. It was used both to improve

  8. Critical Evaluation of Acetylcholine Determination in Rat Brain Microdialysates using Ion-Pair Liquid Chromatography with Amperometric Detection

    Yvette Michotte


    Full Text Available Liquid chromatography with amperometric detection remains the most widely used method for acetylcholine quantification in microdialysis samples. Separation of acetylcholine from choline and other matrix components on a microbore chromatographic column (1 mm internal diameter, conversion of acetylcholine in an immobilized enzyme reactor and detection of the produced hydrogen peroxide on a horseradish peroxidase redox polymer coated glassy carbon electrode, achieves sufficient sensitivity for acetylcholine quantification in rat brain microdialysates. However, a thourough validation within the concentration range required for this application has not been carried out before. Furthermore, a rapid degradation of the chromatographic columns and enzyme systems have been reported. In the present study an ion-pair liquid chromatography assay with amperometric detection was validated and its long-term stability evaluated. Working at pH 6.5 dramatically increased chromatographic stability without a loss in sensitivity compared to higher pH values. The lower limit of quantification of the method was 0.3 nM. At this concentration the repeatability was 15.7%, the inter-day precision 8.7% and the accuracy 103.6%. The chromatographic column was stable over 4 months, the immobilized enzyme reactor up to 2-3 months and the enzyme coating of the amperometric detector up to 1-2 months. The concentration of acetylcholine in 30 μl microdialysates obtained under basal conditions from the hippocampus of freely moving rats was 0.40 ± 0.12 nM (mean ± SD, n = 30. The present method is therefore suitable for acetylcholine determination in rat brain microdialysates.

  9. Thermodynamic Study of the Ion-Pair Complexation Equilibria of Dye and Surfactant by Spectral Titration and Chemometric Analysis

    Hakimeh Abbasi Awal


    Full Text Available Surfactant-dye interactions are very important in chemical and dyeing processes. The dyes interact strongly with surfactant and show new spectrophotometric properties, so the UV-vis absorption spectrophotometric method has been used to study this process and extract some thermodynamic parameters. In this work, the association equilibrium between ionic dyes and ionic surfactant were studied by analyzing spectrophotometric data using chemometric methods. Methyl orange and crystal violet were selected as a model of cationic and anionic dyes respectively. Also sodium dodecyl sulphate and cetyltrimethylammonium bromide were selected as anionic and cationic surfactant, respectively. Hard model methods such as target transform fitting (TTF classical multi-wavelength fitting and soft model method such as multivariate curve resolution (MCR were used to analyze data that were recorded as a function of surfactant concentration in premicellar and postmicellar regions. Hard model methods were used to resolve data using ion-pair model in premicellar region in order to extract the concentration and spectral profiles of individual components and also related thermodynamic parameters. The equilibrium constants and other thermodynamic parameters of interaction of dyes with surfactants were determined by studying the dependence of their absorption spectra on the temperature in the range 293–308 K at concentrations of 5 × 10−6 M and 8 × 10−6 M for dye crystal violet and methyl orange, respectively. In postmicellar region, the MCR-ALS method was applied for resolving data and getting the spectra and concentration profiles in complex mixtures of dyes and surfactants.

  10. Ion-pair hollow-fiber liquid-phase microextraction of the quaternary ammonium surfactant dicocodimethylammonium chloride.

    Hultgren, Sofie; Larsson, Niklas; Nilsson, Bo F; Jönsson, Jan Ake


    A two-phase hollow-fiber (HF) liquid-phase microextraction (LPME) method was developed for determination of a quaternary ammonium compound surfactant, dicocodimethylammonium chloride, in aqueous samples. The porous HF was fixed on a metal rod support and was impregnated with approximately 6.6 microL of organic extractant, which was immobilized in the HF pores. Surfactant extraction was facilitated by addition of carboxylic acid to the sample forming neutral ion pairs with the quaternary ammonium compound. After extraction, the analyte was transferred from the organic extractant in the fiber pores by dissolving the 1-octanol into 100 microL methanol. The methanol extract was analyzed by liquid chromatography-mass spectrometry. The method was optimized (with optimized parameters in brackets) with regard to type of organic extractant (1-octanol), fiber length (2 cm), choice and concentration of anionic carrier (600 microg L(-1) octanoate), procedure of transfer to methanol (15-min sonication), sample volume (250 mL), extraction time (17 h), pH (10), and ionic strength (50 mM carbonate). Aspects influencing repeatability in LPME of (quaternary ammonium) surfactants are discussed. The enrichment factor achieved in 250-mL carbonate buffer was around 400. Due to matrix effects, the enrichment factors achieved when industrial process water was analyzed were 120 or about 30% of that in carbonate buffer. Detection limits of 0.3 microg L(-1) in carbonate buffer and 0.9 microg L(-1) in industrial process water were obtained. If the studied compound is seen as a model substance representing quaternary dialkylated dimethylated ammonium surfactants in general, the developed method may be applied to other quaternary ammonium surfactants.

  11. Effects of electronic structure on the hydration of PbNO3(+) and SrNO3(+) ion pairs.

    Cooper, Richard J; Heiles, Sven; Williams, Evan R


    Hydration of PbNO3(+) and SrNO3(+) with up to 30 water molecules was investigated with infrared photodissociation (IRPD) spectroscopy and with theory. These ions are the same size, yet the IRPD spectra of these ion pairs for n = 2-8 are significantly different. Bands in the bonded O-H region (∼3000-3550 cm(-1)) indicate that the onset of a second hydration shell begins at n = 5 for PbNO3(+) and n = 6 for SrNO3(+). Spectra for [PbNO3](+)(H2O)2-5 and [SrNO3](+)(H2O)3-6 indicate that the structures of clusters with Pb(ii) are hemidirected with a void in the coordinate sphere. A natural bond orbital analysis of [PbNO3](+)(H2O)5 indicates that the anisotropic solvation of the ion is due to a region of asymmetric electron density on Pb(ii) that can be explained by charge transfer from the nitrate and water ligands into unoccupied p-orbitals on Pb(ii). There are differences in the IRPD spectra of PbNO3(+) and SrNO3(+) with up to 25 water molecules attached. IR intensity in the bonded O-H region is blue-shifted by ∼50 cm(-1) in nanodrops containing SrNO3(+) compared to those containing PbNO3(+), indicative of a greater perturbation of the water H-bond network by strontium. The free O-H stretches of surface water molecules in nanodrops containing 10, 15, 20, and 25 water molecules are red-shifted by ∼3-8 cm(-1) for PbNO3(+) compared to those for SrNO3(+), consistent with more charge transfer between water molecules and Pb(ii). These results demonstrate that the different electronic structure of these ions significantly influences how they are solvated.

  12. Influence of carboxylic ion-pairing reagents on retention of peptides in thin-layer chromatography systems with C18 silica-based adsorbents.

    Gwarda, Radosław Ł; Aletańska-Kozak, Monika; Klimek-Turek, Anna; Ziajko-Jankowska, Agnieszka; Matosiuk, Dariusz; Dzido, Tadeusz H


    One of the main problems related to chromatography of peptides concerns adverse interactions of their strong basic groups with free silanol groups of the silica based stationary phase. Influence of type and concentration of ion-pairing regents on peptide retention in reversed-phase high-performance liquid chromatography (RP-HPLC) systems has been discussed before. Here we present influence of these mobile phase additives on retention of some peptide standards in high-performance thin-layer chromatography (HPTLC) systems with C18 silica-based adsorbents. We prove, that due to different characteristic of adsorbents used in both techniques (RP HPLC and HPTLC), influence of ion-pairing reagents on retention of basic and/or amphoteric compounds also may be quite different. C18 silica-based HPTLC adsorbents provide more complex mechanism of retention and should be rather considered as mixed-mode adsorbents. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. An Investigation of Ion-Pairing of Alkali Metal Halides in Aqueous Solutions Using the Electrical Conductivity and the Monte Carlo Computer Simulation Methods.

    Gujt, Jure; Bešter-Rogač, Marija; Hribar-Lee, Barbara


    The ion pairing is, in very dilute aqueous solutions, of rather small importance for solutions' properties, which renders its precise quantification quite a laborious task. Here we studied the ion pairing of alkali halides in water by using the precise electric conductivity measurements in dilute solutions, and in a wide temperature range. The low-concentration chemical model was used to analyze the results, and to estimate the association constant of different alkali halide salts. It has been shown that the association constant is related to the solubility of salts in water and produces a 'volcano relationship', when plotted against the difference between the free energy of hydration of the corresponding individual ions. The computer simulation, using the simple MB+dipole water model, were used to interprete the results, to find a microscopic basis for Collins' law of matching water affinities.

  14. Plasma catecholamines in hypertension and pheochromocytoma determined using ion-pair reversed-phase chromatography with amperometric detection: investigation of the separation mechanism and clinical methodology.

    Krstulović, A M; Dziedzic, S W; Bertani-Dziedzic, L; DiRico, D E


    The retention behavior of catecholamines (CAs) in ion-pair reversed-phase chromatography is examined. From the effects of pH, ionic strength and a secondary ion-pairing reagent (citric acid), under our chromatographic conditions, the retention behavior can be explained by assuming a mixed ion-exchange mechanism with octyl sulfate and citrate, on the column and in the mobile phase, respectively. The developed separation method was applied to the analysis of CAs in plasma samples purified by alumina adsorption and detected amperometrically. This method provides the basis for the determination of the short-term magnitude of CA response to physical and physiological interventions, as well as the baseline CA levels in essential hypertension and pheochromocytoma. The results seen for norepinephrine and epinephrine are consistent with eh funcitonal roles of these CAs as hormones or peripheral transmitters.

  15. Ion pair-based liquid-phase microextraction combined with cuvetteless UV-vis micro-spectrophotometry as a miniaturized assay for monitoring ammonia in waters.

    Senra-Ferreiro, Sonia; Pena-Pereira, Francisco; Costas-Mora, Isabel; Romero, Vanesa; Lavilla, Isela; Bendicho, Carlos


    A miniaturized method based on liquid-phase microextraction (LPME) in combination with microvolume UV-vis spectrophotometry for monitoring ammonia in waters is proposed. The methodology is based on the extraction of the ion pair formed between the blue indophenol obtained according to the Berthelot reaction and a quaternary ammonium salt into a microvolume of organic solvent. Experimental parameters affecting the LPME performance such as type and concentration of the quaternary ammonium ion salt required to form the ion pair, type and volume of extractant solvent, effect of disperser solvent, ionic strength and extraction time, were optimized. A detection limit of 5.0 μg L(-1) ammonia and an enrichment factor of 30 can be attained after a microextraction time of 4 min. The repeatability, expressed as relative standard deviation, was 7.6% (n=7). The proposed method can be successfully applied to the determination of trace amounts of ammonia in several environmental water samples.

  16. Theoretical study of the gas-phase ion pairs SN2 reactions of LiX with CH3SY (X, Y = F, Cl, Br, I)

    Gai, Jing-Gang; Ren, Yi

    The gas-phase ion pair SN2 reactions at saturated sulfur LiX + CH3SY ? CH3SX + LiY (X, Y = F, Cl, Br, I) are investigated using the CCSD(T) calculations. The calculated results show that the reactions LiX + CH3SY are exothermic only when the nucleophile is a heavier lithium halide. Central barrier heights are found to depend primarily on the identity of nucleophile LiX, decreasing in the order LiF > LiCl > LiBr > LiI. Another interesting feature of the ion pair reactions at sulfur is the good correlation between the reaction barriers with geometrical looseness of Li bond X and S bond Y bonds in the transition state structures. The data for the reaction barriers show good agreement with the prediction of the Marcus equation and its modification.

  17. Improvement of Thermal Stability via Outer-Loop Ion Pair Interaction of Mutated T1 Lipase from Geobacillus zalihae Strain T1

    Mahiran Basri


    Full Text Available Mutant D311E and K344R were constructed using site-directed mutagenesis to introduce an additional ion pair at the inter-loop and the intra-loop, respectively, to determine the effect of ion pairs on the stability of T1 lipase isolated from Geobacillus zalihae. A series of purification steps was applied, and the pure lipases of T1, D311E and K344R were obtained. The wild-type and mutant lipases were analyzed using circular dichroism. The Tm for T1 lipase, D311E lipase and K344R lipase were approximately 68.52 °C, 70.59 °C and 68.54 °C, respectively. Mutation at D311 increases the stability of T1 lipase and exhibited higher Tm as compared to the wild-type and K344R. Based on the above, D311E lipase was chosen for further study. D311E lipase was successfully crystallized using the sitting drop vapor diffusion method. The crystal was diffracted at 2.1 Å using an in-house X-ray beam and belonged to the monoclinic space group C2 with the unit cell parameters a = 117.32 Å, b = 81.16 Å and c = 100.14 Å. Structural analysis showed the existence of an additional ion pair around E311 in the structure of D311E. The additional ion pair in D311E may regulate the stability of this mutant lipase at high temperatures as predicted in silico and spectroscopically.

  18. Complementary b/y fragment ion pairs from post-source decay of metastable YahO for calibration of MALDI-TOF-TOF-MS/MS

    Complementary b/y fragment ion pairs from post-source decay (PSD) of metastable YahO protein ion were evaluated for use in the calibration of MALDI-TOF-TOF for tandem mass spectrometry (MS/MS). The yahO gene from pathogenic Escherichia coli O157:H7 strain EDL933 was cloned into a pBAD18 plasmid vect...

  19. [Ion-pair chromatography-indirect ultraviolet detection for determination of tetraethyl ammonium using a monolithic column and a packed column].

    Zou, Chunmiao; Zhang, Xiaodong; Yu, Hong; Guan, Chao; Wang, Miaoyu


    Two methods were developed for the determination of tetraethyl ammonium by ion-pair chromatography-indirect ultraviolet detection using a monolithic column and a packed column with ionic liquid as additive in mobile phase. Chromatographic separations were performed on a monolithic column and a packed column both on reversed phase using imidazolium ionic liquid aqueous solution-ion-pair reagent-organic solvent as mobile phase. The effects of the background ultraviolet absorption reagent, detection wavelength, ion-pair reagent, organic solvent, column temperature and flow rate on the determination of tetraethyl ammonium were investigated. The difference between the two chromatographic columns was compared and the retention rules were discussed. Under the optimized chromatographic conditions, for tetraethyl ammonium on monolithic column and packed column, the retention times were 2.40 and 3.02 min; the detection limits (S/N=3), 0.04 and 0.07 mg/L; the RSDs (n = 5) for peak areas, 0.16% and 0.11%; and the RSDs (n=5) for retention times, 0.02% and 0.01%, respectively. The two methods have been successfully applied to the determination of tetraethyl ammonium ionic liquids synthesized by laboratory. The recoveries of the tetraethyl ammonium after spiking were 98.2% and 99.1%, respectively. The two methods can meet the requirements for the quantitative analysis of tetraethyl ammonium.

  20. Validated ion pair liquid chromatography/fluorescence detection method for assessing the variability of the loratadine metabolism occurring in bioequivalence studies.

    Sora, Daniela Iuliana; Udrescu, Stefan; David, Victor; Medvedovici, Andrei


    Inter- and intra-individual variability of the loratadine (LOR) metabolism in Caucasian subjects was assessed during a bioequivalence study for two pharmaceutical formulations (solid oral dosage forms) containing 10 mg of the active substance. The analytical data were obtained by applying a reliable, low-cost and sensitive ion pair liquid chromatography/fluorescence (IPLC/FLD) method for determination of both loratadine and descarboethoxyloratadine (DCL) in human plasma samples. The sample preparation procedure is based on liquid-liquid extraction of the target analytes from alkalinized plasma using diethyl-ether. The separation of the analytes and 8-chloroazatadine as internal standard (IS) was achieved through an isocratic ion pair (IP) elution on a Purospher((R)) STAR RP-18 column. The mobile phase containing sodium dodecyl sulfate (SDS) as ion pairing agent was pumped at a flow rate of 1 mL/min. Fluorescence detection (FLD) was achieved at 280 nm (excitation) and 440 nm (emission) wavelengths. The increased sensitivity of the method is also based on a large sample injected volume (250 microL). Linear response was found over the 0.5-20 ng/mL concentration interval for both target compounds. Low limits of quantification (LLOQ) around 0.3 ng/mL were found for LOR and DCL. Method validation is presented.

  1. Syntheses, crystal structures, electronic spectra and magnetic properties of two ion-pair charge transfer complexes based on [Ni(mnt)2]-

    Xu, Xiao-Yi; Chen, Xuan-Rong; Yang, Qing-Cheng; Xue, Chen; Tao, Jian-Qing; Liu, Jian-Lan; Ren, Xiao-Ming


    Two new bimetallic ion-pair complexes 1 and 2 with general formula [M(phen)3][Ni(mnt)2]2 (phen = 1, 10-phenanthroline, mnt2- = maleonitriledithiolate; M = Ni2+, Fe2+ for 1 and 2), have been prepared and characterized by IR, elemental analysis, single crystal X-ray diffraction, UV-vis-NIR spectra and magnetic measurements. The structural determination reveals that the crystals of two ion-pair complexes, with monoclinic space group C2/c, have similar cell parameters and the [M(phen)3]2+ cations and the [Ni(mnt)2]- anions are packed by forming alternate layers. Thermogravimetric (TG) analyses revealed that 1 and 2 are thermally stable up to ∼170 °C. UV-vis-NIR spectra discloses that two complexes exhibit sizable absorption in near-IR region because of ion-pair charge transfer (IPCT) transitions in 1 and 2. Investigation of the magnetic properties 1 shows Curie-Weiss-type paramagnetic behavior in the temperature range 2-400 K. For 2, the paramagnetic behavior above ∼40 K indicated the [Fe(phen)3]2+ ion has a low-spin state and the weak Curie-Weiss type tail below 40 K results from a trace amount of paramagnetic [Ni(mnt)2]- species.

  2. Operator care and eco-concerned development of a fast, facile and economical assay for basic nitrogenous drugs based on simplified ion-pair mini-scale extraction using safer solvent combined with drop-based spectrophotometry.

    Plianwong, Samarwadee; Sripattanaporn, Areerut; Waewsa-nga, Kwanrutai; Buacheen, Parin; Opanasopit, Praneet; Ngawhirunpat, Tanasait; Rojanarata, Theerasak


    A fast, facile, and economical assay for basic nitrogenous drugs has been developed based on the mini-scale extraction of the drug-dye ion pair complex combined with the use of safe-for-analyst and eco-friendlier organic extractant and drop-based micro-spectrophotometry. Instead of using large volume devices, the extraction was simply carried out in typical 1.5 mL microcentrifuge tubes along with the use of micropipettes for accurate transfer of liquids, vortex mixer for efficient partitioning of solutes and benchtop centrifuge for rapid phase separation. In the last step, back-extraction was performed by using the microvolume of acidic solution in order to concentrate the colored species into a confined aqueous microdrop and to keep the analyst away from unwanted contact and inhalation of organic solvents during the quantitation step which was achieved by using cuvetteless UV-vis micro-spectrophotometry without any prior dilutions. Using chlorpheniramine maleate as a representative analyte and n-butyl acetate as a less toxic and non-ozone depleting extractant, the miniaturized method was less laborious and much faster. It was accurate, precise and insensitive to the interferences from common excipients. Notably, it gave the assay results of drug in tablets and oral solution comparable to the large-scale pharmacopeial method while the consumption of organic solvents and the release of wastes were lowered by 200-400 folds.

  3. A chemical approach for site-specific identification of NMR signals from protein side-chain NH{sub 3}{sup +} groups forming intermolecular ion pairs in protein–nucleic acid complexes

    Anderson, Kurtis M. [University of Texas Health Science Center at Houston, Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine (United States); Nguyen, Dan; Esadze, Alexandre; Zandrashvili, Levani [University of Texas Medical Branch, Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics (United States); Gorenstein, David G. [University of Texas Health Science Center at Houston, Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine (United States); Iwahara, Junji, E-mail:, E-mail: [University of Texas Medical Branch, Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics (United States)


    Protein–nucleic acid interactions involve intermolecular ion pairs of protein side-chain and DNA or RNA phosphate groups. Using three protein–DNA complexes, we demonstrate that site-specific oxygen-to-sulfur substitution in phosphate groups allows for identification of NMR signals from the protein side-chain NH{sub 3}{sup +} groups forming the intermolecular ion pairs. A characteristic change in their {sup 1}H and {sup 15}N resonances upon this modification (i.e., substitution of phosphate to phosphorodithioate) can represent a signature of an intermolecular ion pair. Hydrogen-bond scalar coupling between protein side-chain {sup 15}N and DNA phosphorodithiaote {sup 31}P nuclei provides direct confirmation of the intermolecular ion pair. The same approach is likely applicable to protein–RNA complexes as well.

  4. [A simultaneous determination of honokiol and mangolol in Oriental pharmaceutical decoctions containing magnolia bark by ion-pair high-performance liquid chromatography. II].

    Ueda, J; Asaka, N; Tanaka, I; Hayashi, Y; Hirose, Y; Momma, N; Yasuda, T; Ohsawa, K


    A simple method using ion-pair high-performance liquid chromatography was established for the rapid and precise determination of honokiol(3',5-di-2-propenyl-1,1'-biphenyl-2,4'-diol) and magnolol(5,5'-di-2-propenyl-1,1'-biphenyl-2,2'-diol) in eighteen species of oriental pharmaceutical decoctions containing Magnolia bark. An ODS column and a mixed solvent system of water involving 10 mM tetra-n-amyl-ammonium bromide (TAA) and acetonitrile (4:6) as a mobile phase were used for the separation. Honokiol and magnolol were eluted without interference of other coexisting components within 12 min.

  5. Dispersive solid phase extraction combined with ion-pair ultra high-performance liquid chromatography tandem mass spectrometry for quantification of nucleotides in Lactococcus lactis

    Magdenoska, Olivera; Martinussen, Jan; Thykær, Jette


    during the quenching. Using a Phenyl-Hexyl column and tributylamine as volatile ion-pair reagent, sufficient retention and separation was achieved for mono-, di-, and triphosphorylated nucleotides. Stable isotope labeled nucleotides were used as internal standards for some analytes. The method...... was validated by determination of the recovery, matrix effects, accuracy, linearity, and limit of detection based on spiking of medium blank as well as standard addition to quenched Lactococcus lactis samples. For standard addition experiments, the isotope-labeled standards needed to be added in similar...

  6. Aspects on the catalysis of lipase from porcine pancreas (type VI-s) in aqueous media: development of ion-pairs


    This article reports a first contribution for the elucidation of catalytic mechanism of Lipase from porcine pancreas, type VI-s (PPL), in hydrolyzing an ester substrate in aqueous media. The conclusions were based on the pH-profiles of Michaelis-Menten parameters k cat/Km, k cat and Km, as well as on the absolute temperature profile of k cat/Km, obtained during the hydrolysis of p-nitrophenyl laurate by PPL. It was found that (a) PPL performs catalysis by means of ion pairs formed either as S...

  7. The structure of ([W3Q4X3(dmpe)3]+, Y-) ion pairs (Q = S, Se; X = H, OH, Br; Y = BF4, PF6, dmpe = Me2PCH2CH2PMe2) in dichloromethane solution and the effect of ion-pairing on the kinetics of proton transfer to the hydride cluster [W3S4H3(dmpe)3]+.

    Algarra, Andrés G; Basallote, Manuel G; Fernandez-Trujillo, M Jesús; Llusar, Rosa; Safont, Vicent S; Vicent, Cristian


    The 1H,19F HOESY spectra of the title compounds in CD2Cl2 solution indicate that the cluster cations form ion pairs with the BF4- and PF6- anions with a well-defined interionic structure that appears to be basically determined essentially by the nature of the X- ligand. For the clusters with X = H and OH, the structure of the ion pairs is such that the counteranion (Y-) and the X- ligands are placed close to each other. However, when the size and electron density of X- increase (X = Br), Y- is forced to move to a different site, far away from X-. The relevance of ion-pairing on the chemistry of these compounds is clearly seen through a decrease in the rate of proton transfer from HCl to the hydride cluster [W3S4H3(dmpe)3]+ in the presence of an excess of BF4-. The kinetic data for this reaction can be rationalized by considering that the ([W3S4H3(dmpe)3]+, BF4-) ion pairs are unproductive in the proton-transfer process. Theoretical calculations indicate that the real behavior can be more complex. Although the cluster can still form adducts with HCl in the presence of BF4-, the structures of the most-stable BF4--containing HCl adducts show H...H distances too large to allow the subsequent release of H2. In addition, the effective concentration of HCl is also reduced because of the formation of adducts as ClH...BF4-. As a consequence of both effects, the proton transfer takes place more slowly than for the case of the dihydrogen-bonded HCl adduct resulting from the unpaired cluster.

  8. Ion pair-based dispersive liquid-liquid microextraction followed by high performance liquid chromatography as a new method for determining five folate derivatives in foodstuffs.

    Nojavan, Yones; Kamankesh, Marzieh; Shahraz, Farzaneh; Hashemi, Maryam; Mohammadi, Abdorreza


    A novel technique for simultaneous determination of five folate derivatives in various food matrices was developed by ion pair-based dispersive liquid-liquid microextraction (IP-DLLME) combined with high-performance liquid chromatography (HPLC). In the proposed method, N-methyl-N,N-dioctyloctan-1-ammonium chloride (aliquat-336) was used as an ion-pair reagent. Effective variables of microextraction process were optimized. Under optimum conditions, the method yielded a linear calibration curve ranging from 1-200 ng g(-1) with correlation coefficients (r(2)) higher than 0.98. The relative standard deviation for the seven analyses was 5.2-7.4%. Enrichment factors for the five folates ranged between 108-135. Limits of detection were 2-4.1 ng g(-1). A comparison of this method with other methods described that the new proposed method is rapid and accurate, and gives very good enrichment factors and detection limits for determining five folate derivatives. The newly developed method was successfully applied for the determination of five folate derivatives in wheat flour, egg yolk and orange juice samples.

  9. An intravenous clarithromycin lipid emulsion with a high drug loading, H-bonding and a hydrogen-bonded ion pair complex exhibiting excellent antibacterial activity

    Haoyu Gong


    Full Text Available The aim of this study was to develop an intravenous clarithromycin lipid emulsion (CLE with good stability and excellent antibacterial activity. The CLE was prepared by the thin-film dispersed homogenization method. The interaction between clarithromycin (CLA and cholesteryl hemisuccinate (CHEMS was confirmed by DSC, FT-IR and 1H NMR analysis. The interfacial drug loading, thermal sterilization, freeze–thaw stability, and in vitro and in vivo antibacterial activity were investigated systematically. DSC, FT-IR and 1H NMR spectra showed that CHEMS (CLA: CHEMS, M ratio 1:2 could interact with CLA through H-bonding and a hydrogen-bonded ion pair. The CHEMS was found necessary to maintain the stability of CLE. Ultracentrifugation showed that almost 88% CLA could be loaded into the interfacial layer. The optimized CLE formulation could withstand autoclaving at 121 °C for 10 min and remain stable after three freeze–thaw cycles. The in vitro susceptibility test revealed that the CLA–CHEMS ion-pair and CLE have similar activity to the parent drug against many different bacterial strains. The in vivo antibacterial activity showed that the ED50 of intravenous CLE was markedly lower than that of CLA solution administrated orally. CLE exhibited pronounced antibacterial activity and might be a candidate for a new nanocarrier for CLA with potential advantages over the current commercial formulation.

  10. On-line solid phase extraction using ion-pair microparticles combined with ICP-OES for the simultaneous preconcentration and determination of uranium and thorium

    Yousefi, Seyed Reza; Zolfonoun, Ehsan [Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of). NFCRS


    In this work, after on-line and in-situ solid phase extraction technique was used for the extraction and preconcentration of uranium and thorium from aqueous samples prior to inductively coupled plasma optical emission spectrometry (ICP-OES) determination. In this method, sodium hexafluorophosphate (as an ion-pairing agent) was added to the sample solution containing the cationic surfactant (dodecyltrimethylammonium bromide) and the complexing agent (dibenzoylmethane). A cloudy solution was formed as a result of formation of an ion pair between surfactant and hexafluorophosphate. The solid microparticles were passed through a microcolumn filter and the adsorbed microparticles were subsequently eluted with acid, which was directly introduced into the ICP-OES nebulizer. The main variables affecting the pre-concentration and determination steps of uranium and thorium were studied and optimized. Under the optimum conditions, the enhancement factors of 97 and 95 and the detection limits of 0.52 and 0.21 μg L{sup -1} were obtained for uranium and thorium, respectively.

  11. Sensitive and selective spectrophotometric assay of piroxicam in pure form, capsule and human blood serum samples via ion-pair complex formation.

    Alizadeh, Nina; Keyhanian, Fereshteh


    A simple, accurate and highly sensitive spectrophotometric method has been developed for the rapid determination of piroxicam (PX) in pure and pharmaceutical formulations. The proposed method involves formation of stable yellow colored ion-pair complexes of the amino derivative (basic nitrogen) of PX with three sulphonphthalein acid dyes namely; bromocresol green (BCG), bromothymol blue (BTB), bromophenol blue (BPB) in acidic medium. The colored species exhibited absorption maxima at 438, 429 and 432 nm with molar absorptivity values of 9.400×10(3), 1.218×10(3) and 1.02×10(4) L mol(-1) cm(-1) for PX-BCG, PX-BTB and PX-BPB complexes, respectively. The effect of optimum conditions via acidity, reagent concentration, time and solvent were studied. The reactions were extremely rapid at room temperature and the absorbance values remained constant for 48h. Beer's law was obeyed with a good correlation coefficient in the concentration ranges 1-100 μg mL(-1) for BCG, BTB complexes and 1-95 μg mL(-1) for BPB complex. The composition ratio of the ion-pair complexes were found to be 1:1 in all cases as established by Job's method. No interference was observed from common additives and excipients which may be present in the pharmaceutical preparations. The proposed method was successfully applied for the determination of PX in capsule and human blood serum samples with good accuracy and precision.

  12. Ion pair-dispersive liquid-liquid microextraction coupled to microsample injection system-flame atomic absorption spectrometry for determination of gold at trace level in real samples.

    Hol, Aysen; Kartal, Aslıhan Arslan; Akdogan, Abdullah; Elçi, Aydan; Arslan, Tuba; Elçi, Lati


    A novel ion pair-dispersive liquid-liquid microextraction (IP-DLLME) of gold followed by its determination with microsample injection system-flame atomic absorption spectrometry (MIS-FAAS) detection was developed. The extraction method was based on the reaction of anionic tetrachloro gold(III) complex with the cationic form of Rhodamine B to give a violet ion pair complex, which is extracted from 1.0 mol L(-1) HCl solution of 8.0 mL to fine droplets of chloroform of 500 µL. A Plackett-Burman experimental design of MINITAB statistical program was employed to optimize the influence of main parameters to be controlled in DLLME. After optimizing the extraction conditions, gold was quantitatively recovered by preconcentration factor of 40, limit of detection (LOD) of 1.8 μg L(-1) and relative standard deviation of less than 6.8%. The proposed method was successfully applied to the preconcentration and determination of gold in some samples such as tap water, waste water, copper electrolysis solution and copper wire coated nickel.

  13. Extractive spectrophotometric determination of five selected drugs by ion-pair complex formation with bromothymol blue in pure form and pharmaceutical preparations

    Sneha G. Nair


    Full Text Available Simple, precise, selective, and expeditious spectrophotometric methods have been developed for the determination of itopride (ITO, midodrine (MID, diclofenac (DIC, mesalamine (MES, and sumatriptan (SUM in their pure form as well as in pharmaceutical preparations. The method was based on ion-pair complex formation between the drugs and anionic dye, bromothymol blue in an acidic medium (pH 2.0–4.0. The yellow colored complexes formed were quantitatively extracted into chloroform and measured at 411, 410, 413, 412, and 414 nm wavelength for ITO, MID, DIC, MES, and SUM, respectively. Beer’s law was obeyed in the concentration range of 3.0–30 µg/mL for ITO, 1.0–20 µg/mL for MID, 1.5–40 µg/mL for DIC, 1.2–12 µg/mL for MES, and 0.5–15 µg/mL for SUM. The stoichiometry of the complexes formed between the drugs and the dye was 1:1 as determined by Job’s method of continuous variation. The association constant (KIP of the ion-pair complexes formed was evaluated using Benesi–Hildebrand equation. Limit of detection, limit of quantification, and Sandell’s sensitivity of the methods were also estimated. The proposed methods were successfully employed for the determination of these drugs in their pharmaceutical dosage forms.

  14. The simultaneous determination of active ingredients in cough-cold mixtures by isocratic reversed-phase ion-pair high-performance liquid chromatography.

    Lau, O W; Chan, K; Lau, Y K; Wong, W C


    A simple, rapid and accurate method for the simultaneous determination of active ingredients in cough-cold mixtures using isocratic reversed-phase ion-pair high-performance liquid chromatography has been developed. It involves the use of an octadecylsilane column as the stationary phase with methanol, water, tetrahydrofuran, phosphoric acid mixtures as mobile phase including sodium dioctylsulphosuccinate as the ion-pair agent. The pH of the mobile phase was adjusted to 4.6 by means of phosphoric acid and ammonium hydroxide solutions. The proposed method involves the simple dilution of the samples with the mobile phase and the addition of metoclopramide hydrochloride as the internal standard. The active ingredients under investigation were chlorpheniramine, codeine, diphenhydramine, ephedrine, ethylmorphine, phenylephrine, phenylpropanolamine and pholcodine, which exist as various combinations in cough-cold mixtures. The optimum composition of the mobile phase and the optimum flow rate were determined and are reported. The method was applied to the determination of active ingredients in seven commercially available cough-cold mixtures.

  15. Extractive spectrophotometric determination of sulphonamide drugs in pure and pharmaceutical preparations through ion-pair formation with molybdenum(V thiocyanate in acidic medium

    Faten A. Nour El-Dien


    Full Text Available A simple and sensitive extraction-spectrophotometric method is described for the determination of sulfonamide drugs, namely sulphamethoxazole, sulphaguanidine, sulphaquinoxaline, sulphametrole and sulphadimidine, in both pure form and in the dosage forms available in Egyptian markets. The method is based on ion-pair formation between the sulphonamides and Mo(V-thiocyanate inorganic complex in a sulphuric acid medium followed by extraction of the coloured ion-pairs with 1,2-dichloroethane. The optimum conditions are established. The method permits the determination of sulphonamide drugs over the concentration range of 5–50 μg ml−1. The Sandell sensitivity (S, molar absorptivity, correlation coefficient and regression equations, and limits of detection (LOD and quantification (LOQ are calculated. The law values of standard deviation (0.09–0.38 and relative standard deviation (0.10–0.550 reflect the accuracy and precision of the proposed method. The method is applicable for the assay of the investigated drugs in different dosage forms and the results are in good agreement with those obtained by the official pharmacopeial method.

  16. High performance liquid chromatography for the simultaneous analysis of penicillin residues in beef and milk using ion-paired extraction and binary water-acetonitrile mixture.

    Kukusamude, Chunyapuk; Burakham, Rodjana; Chailapakul, Orawon; Srijaranai, Supalax


    An ion-paired extraction (IPE) has been developed for the analysis of penicillin antibiotics (penicillin G, oxacillin and cloxacillin) in beef and milk samples using tetrabutylammonium bromide (TBABr) as ion-pairing agent and binary water-acetonitrile as extractant. The factors affecting the IPE efficiency were optimized including solution pH, volume of acetonitrile (ACN), concentration of TBABr and electrolyte salt (NH(4))(2)SO(4). The optimum IPE conditions were 10 mmol L(-1) phosphate buffer pH 8, 2 mL of ACN, 6 mmol L(-1) of TBABr and 2.5 mL of saturated ammonium sulfate. Under the HPLC condition: an Xbridge™ C18 reversed-phase column, isocratic elution of 5 mmol L(-1) phosphate buffer (pH 6.6) and acetonitrile (75:25, v/v) and a flow rate of 1 mL min(-1), with UV detection at 215 nm, the separation of three penicillins was achieved within 10 min. Under the selected optimum conditions, the enhancement of 21-53 folds compared to that without preconcentration and limits of detection (LODs) of 1-2 ng mL(-1) were obtained. Good reproducibility was achieved with RSDpenicillin residues in beef and milk with LOD lower than the maximum residue limits.

  17. Supercritical fluid chromatographic resolution of water soluble isomeric carboxyl/amine terminated peptides facilitated via mobile phase water and ion pair formation.

    Patel, M A; Riley, F; Ashraf-Khorassani, M; Taylor, L T


    Both analytical scale and preparative scale packed column supercritical fluid chromatography (SFC) have found widespread applicability for chiral separations of multiple polar pharmaceutical candidates. However, SFC is rapidly becoming an achiral technique. More specifically, ion pair SFC is finding greater utility for separation of ionic analytes such as amine salts and organic sulfonates. The key to this success is, in part, the incorporation of additives such as trifluoroacetic acid and ammonium acetate into the mobile phase in association with a wide variety of both bonded silica stationary phases and high purity bare silica. Ion pairing SFC coupled with evaporative light scattering detection and mass spectrometric detection is presented here for the separation of water soluble, uncapped, isomeric peptide pairs that differ in amino acid arrangement. The separation is best achieved on either diol-bonded silica or bare silica with 1-5% (w/w) water as a significant ingredient in the mobile phase. Nitrogenous stationary phases such as 2-ethylpyridine, which had been very successful for the separation of capped peptides failed to yield the desired separation regardless of the mobile phase composition. A HILIC type retention mechanism is postulated for the separation of both isomeric uncapped peptide pairs.




    Determination of low-molecular-weight organic sulfonates (e.g. taurine and cysteic acid) in aqueous solutions is important in many applications of biological, environmental and pharmaceutical sciences. These compounds are difficult to be determined by commonly used reversed-phase liquid chromatographic separation combined with UV-Visible detection because of their high solubility and the lack chromophoric moieties. Here the authors report a method combining ion-pair liquid chromatography and electrospray ionization tandem mass spectrometry (IPLC/ESI-MS/MS)for determining sulfonates. The ability of low-molecular-weight sulfonates to form ion-pairs with quaternary ammonium cations in aqueous solutions allowed LC separation with a C{sub 18} column. Detection of the sulfonates was accomplished with ESI-MS that lends a universal mode of mass detection for polar, water soluble compounds. An in-source collision induced dissociation (CID) was applied to eliminate the adduct peaks in mass spectra. Characteristic marker ions showed in the second stage mass spectra lent a method for identifying sulfonates.

  19. Organic solvent-free reversed-phase ion-pairing liquid chromatography coupled to atomic fluorescence spectrometry for organoarsenic species determination in several matrices.

    Monasterio, Romina P; Londonio, Juan A; Farias, Silvia S; Smichowski, Patricia; Wuilloud, Rodolfo G


    A novel method has been developed to determine As-containing animal feed additives including roxarsone (ROX), p-arsanilic acid (p-ASA) and nitarsone (NIT), as well as other organic As species (dimethylarsonic acid (DMAA) and monomethylarsonic acid (MMAA)) by ion-pairing high-performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry (IP-HPLC-HG-AFS). A simple isocratic reversed-phase (RP) HPLC method with a mobile phase containing citric acid and sodium hexanesulfonate (pH 2.0) was developed using a C(18) column. The use of an organic solvent free mobile phase turns this methodology into an environmentally friendly alternative. Several ion pair forming agents, such as sodium hexanesulfonate, tetrabutylammonium bisulfate and perfluoroheptanoic acid, were studied. The limits of detection for As species were calculated in standard solution and resulted to be 0.2, 0.5, 0.6, 1.6, and 1.6 μg As L(-1) for MMAA, DMAA, p-ASA, ROX and NIT, respectively. This method exhibited convenient operation, high sensitivity and good repeatability. It was applied to As speciation in different samples including arugula, dog food, dog urine and chicken liver.

  20. Sensitive and selective spectrophotometric assay of piroxicam in pure form, capsule and human blood serum samples via ion-pair complex formation

    Alizadeh, Nina; Keyhanian, Fereshteh


    A simple, accurate and highly sensitive spectrophotometric method has been developed for the rapid determination of piroxicam (PX) in pure and pharmaceutical formulations. The proposed method involves formation of stable yellow colored ion-pair complexes of the amino derivative (basic nitrogen) of PX with three sulphonphthalein acid dyes namely; bromocresol green (BCG), bromothymol blue (BTB), bromophenol blue (BPB) in acidic medium. The colored species exhibited absorption maxima at 438, 429 and 432 nm with molar absorptivity values of 9.400 × 103, 1.218 × 103 and 1.02 × 104 L mol-1 cm-1 for PX-BCG, PX-BTB and PX-BPB complexes, respectively. The effect of optimum conditions via acidity, reagent concentration, time and solvent were studied. The reactions were extremely rapid at room temperature and the absorbance values remained constant for 48 h. Beer’s law was obeyed with a good correlation coefficient in the concentration ranges 1-100 μg mL-1 for BCG, BTB complexes and 1-95 μg mL-1 for BPB complex. The composition ratio of the ion-pair complexes were found to be 1:1 in all cases as established by Job’s method. No interference was observed from common additives and excipients which may be present in the pharmaceutical preparations. The proposed method was successfully applied for the determination of PX in capsule and human blood serum samples with good accuracy and precision.

  1. Characterization of synthetic dyes by comprehensive two-dimensional liquid chromatography combining ion-exchange chromatography and fast ion-pair reversed-phase chromatography.

    Pirok, Bob W J; Knip, Jitske; van Bommel, Maarten R; Schoenmakers, Peter J


    In the late 19th century, newly invented synthetic dyes rapidly replaced the natural dyes on the market. The characterization of mixtures of these so-called early synthetic dyes is complicated through the occurrence of many impurities and degradation products. Conventional one-dimensional liquid chromatography does not suffice to obtain fingerprints with sufficient resolution and baseline integrity. Comprehensive two-dimensional liquid chromatography (LC×LC) is employed in this study, with ion-exchange chromatography in the first dimension and fast ion-pair liquid chromatography in the second. Retention in the first dimension is largely determined by the number of charges, while the selection of a small ion-pair reagent (tetramethylammonium hydroxide) in the second dimension causes retention to be largely determined by the molecular structure of the dye. As a result, there is a high degree of orthogonality of the two dimensions, similar to the values typically encountered in GC×GC. The proposed LC×LC method shows a theroretical peak capacity of about 2000 in an analysis time of about three hours. Clear, informative fingerprints are obtained that open a way to a more efficient characterization of dyes used in objects of cultural heritage.

  2. Rate theory of solvent exchange and kinetics of Li+ - BF4-/PF6- ion pairs in acetonitrile

    Dang, Liem X. [Physical Science Division, Pacific Northwest National Laboratory, Richland, Washington 93352, USA; Chang, Tsun-Mei [Department of Chemistry, University of Wisconsin - Parkside, Kenosha, Wisconsin 53141, USA


    In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li+(aq) and the kinetics of ion pairings in lithium-ion batteries (LIB). We report one of the first computer simulations of the exchange dynamics around hydrated Li+ in acetonitrile (ACN), which is common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li+-[BF4] and Li+-[PF6] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li+(aq). We calculate exchange rates using transition state theory and weighted them with transmission coefficients determined by the reactive flux and Impey, Madden, and McDonald approaches and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li+-[BF4] and Li+-[PF6] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems.

  3. Theoretical study on the identity ion pair SN2 reactions of LiX with CH3SX (X=Cl, Br, and I): structure, mechanism, and potential energy surface.

    Ren, Yi; Gai, Jing-Gang; Xiong, Yan; Lee, Kuo-Hsing; Chu, San-Yan


    Three archetypal ion pair nucleophilic substitution reactions at the methylsulfenyl sulfur atom LiX+CH3SX-->XSCH3+LiX (X=Cl, Br, and I) are investigated by the modified Gaussian-2 theory. Including lithium cation in the anionic models makes the ion pair reactions proceed along an SN2 mechanism, contrary to the addition-elimination pathway occurring in the corresponding anionic nucleophilic substitution reactions X-+CH3SX-->XSCH3+X-. Two reaction pathways for the ion pair SN2 reactions at sulfur, inversion and retention, are proposed. Results indicate the inversion pathway is favorable for all the halogens. Comparison of the transition structures and energetics for the ion pair SN2 at sulfur with the potential competition ion pair SN2 reactions at carbon LiX+CH3SX-->XCH3+LiXS shows that the SN2 reactions at carbon are not favorable from the viewpoints of kinetics and thermodynamics.

  4. [A simultaneous determination of daidzin and puerarin and determination of daidzein in Oriental pharmaceutical decoctions containing puerariae radix by ion-pair high-performance liquid chromatography].

    Yasuda, T; Momma, N; Ohsawa, K


    A simple and precise method was established for the simultaneous determination of daidzin and puerarin and the determination of daidzein in oriental pharmaceutical decoctions containing Puerariae Radix using high-performance liquid chromatography with tetra-n-heptylammonium bromide (THA) as an ion-pair reagent. Daidzin and puerarin were eluted within 45 min without interference with co-existing components using an ODS column and a mixture of 10 mM phosphate buffer (pH 6.5)-methanol (68:32) containing 5 mM THA as a mobile phase. Daidzein was eluted within 35 min without interference with co-existing components using an ODS column and a mixture of 10 mM phosphate buffer (pH 6.5)-acetonitrile (72:28 or 68:32) containing 5 mM THA as a mobile phase.

  5. Investigation of a new core-shell particle column for ion-pair reversed-phase liquid chromatography analysis of oligonucleotides.

    Biba, Mirlinda; Welch, Christopher J; Foley, Joe P


    A new core-shell particle column showed excellent performance and durability for separation of short (∼21-mer) ribonucleic acid (RNA) oligonucleotides by ion-pair reversed-phase liquid chromatography (IP-RPLC). Previously investigated core-shell C18 columns showed excellent peak shapes and separations of closely eluting impurities by IP-RPLC. However, these columns showed only modest long-term stability at the neutral pH and elevated column temperatures of ≥60°C, typically used for IP-RPLC analysis of oligonucleotides. The newly introduced SunShell C18 column provided separations comparable to the previously evaluated core-shell columns, but with significantly improved long-term column stability when operated at neutral pH and elevated column temperature.

  6. Application of a radioactivity detector to the analysis of /sup 14/C-Carmoisine metabolites by ion-pair high-pressure liquid chromatography

    Tragni, E.; Costa, L.G.; Marinovich, M.; Galli, C.L.


    /sup 14/C-Carmoisine was incubated under anaerobic conditions with a suspension of human feces. Analyses of the incubation medium by high-performance liquid chromatography (HPLC) attached to a radioactivity monitor (RAM) showed the same radioactivity profile as the urine and feces of rats dosed with the same azodye (200 mg kg-1; 25 microCi). The analyses were carried out with a 5 micron RP-C18 chromatographic column, using a linear gradient profile of different concentrations of water, methanol and an ion-pair reagent. Five radioactive peaks were present in the radiochromatogram , in addition to unmodified Carmoisine. The major peak retained half of the specific activity of Carmoisine, and exhibited the retention time and the u.v. spectrum of authentic naphthionic acid. The results demonstrate the value and the advantage of using the in vitro preparation as a model to detect and to identify the metabolites of similar synthetic azodyes used as food additives.

  7. Determination of benzylpenicillin, oxacillin, cloxacillin, and dicloxacillin in cows' milk by ion-pair high-performance liquid chromatography after precolumn derivatization.

    Marchetti, M; Schwaiger, I; Schmid, E R


    A high-performance liquid-chromatographic method has been developed for the determination of five penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, oxacillin, cloxacillin, and dicloxacillin) at trace levels in commercially available milk samples. This method comprises extraction of the lipids with ethyl acetate, clean-up and concentration on a C-18 solid-phase extraction column, and derivatization with 1,2,4-triazole and mercury(II) chloride solution, pH 8, at 65 degrees C for 10 min. The derivatized compounds are eluted from a C-2 column with a mobile phase containing acetonitrile and phosphate buffer loaded with sodium thiosulfate and tetrabutylammonium hydrogen sulfate as ion-pairing reagent. The limit of determination was found to be 4 microg L(-1) milk for benzylpenicillin and 10 microg L(-1) for the others. This meets EU criteria according to decision No. 93/256/EEC.

  8. Biosynthesis of Cd-bound phytochelatins by Phaeodactylum tricornutum and their speciation by size-exclusion chromatography and ion-pair chromatography coupled to ICP-MS.

    Loreti, Valeria; Toncelli, Daniel; Morelli, Elisabetta; Scarano, Gioacchino; Bettmer, Jörg


    Cd-bound phytochelatins (Cd-PCs) have been synthesised by incubation of Phaeodactylum tricornutum cell cultures with Cd and purified by size-exclusion chromatography-UV-Vis. These complexes, which were identified in previous work, have now been used as model substances to develop and optimise ion-pair chromatography (IPC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) for analysis of Cd-PCs. Subsequent analysis of samples taken from Silene vulgaris plants cultivated under heavy metal stress conditions revealed Cd signals but no Cd-PC signals. By use of isotopically enriched (116)Cd-PCs the sample preparation steps were verified to determine the stability of the analytes. We observed species transformation between Cd-PCs and other unidentified Cd complexes. Consequently, the kinetic and thermodynamic lability of Cd-PCs are decisive factors in their detection.

  9. Determination of nucleosides and nucleotides in baby foods by hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of hydrophilic ion-pairing reagents.

    Mateos-Vivas, María; Rodríguez-Gonzalo, Encarnación; Domínguez-Álvarez, Javier; García-Gómez, Diego; Carabias-Martínez, Rita


    In this work we propose a rapid and efficient method for the joint determination of nucleosides and nucleotides in dairy and non-dairy baby foods based on hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of diethylammonium (DEA) as a hydrophilic ion-pairing reagent (IP-HILIC-MS/MS). Sample treatment of the baby food included dilution with water and centrifugal ultrafiltration (CUF) with an additional washing step that notably improved the global performance of the process. Later dilution of the extract with acetonitrile allowed adequate separation in the HILIC system. With the proposed treatment, we obtained extraction recoveries higher than 80% and, additionally, no matrix effects were observed. The CUF-IP-HILIC-MS/MS method was validated according to the 2002/657/EC decision and was used for the quantification of nucleotides and nucleosides in sixteen samples of commercial baby foods. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. [Simultaneous determination of five active components of compound α-ketoacid tablet in human urine by ion-pair reversed-phase high performance liquid chromatography].

    Huang, Xiaoya; Zhong, Yuan; Huang, Zhongping; Jin, Chen; Wang, Lili; Pan, Zaifa


    A simple and sensitive method for the simultaneous determination of five active components, D, L-α-hydroxymethionine calcium (HMACa), α-ketovaline calcium (KVCa), D, L-α-ketoisoleucine calcium (KILCa), α-ketoleucine calcium (KLCa) and α-ketophenylalanine calcium (KPACa) of compound α-ketoacid tablet in human urine by ion-pair reversed-phase high performance liquid chromatography (RP-HPLC) was developed and validated. The separation conditions, such as the concentration of ion-pair reagent, the pH value of the mobile phase and the concentration of the buffer were optimized. All the five analytes were separated well on a C18 column (250 mm x 4.6 mm, 5 µm) with diode array detection at 210 nm and the column temperature of 35 °C. The mobile phases were acetonitrile and 20 mmol/L phosphate buffer (containing 15 mmol/L tetrabutylammonium hydroxide; pH 7) at the flow rate of 1. 0 mL/min with gradient elution. The calibration curves for the five components were linear in the range from 20 to 200 mg/L (r≥ 0. 9990). The limits of detection (LODs, S/N= 3) were 3.0, 5. 0, 3. 6, 5.7 and 2. 5 mg/L, and the limits of quantification (LOQs, S/N= 10) were 9. 6, 16.7, 12.0, 19.0 and 8.3 mg/L for HMACa, KVCa, KILCa, KLCa and KPACa, respectively. The intra-day and inter-day precisions were less than 7%, and the average recoveries were between 86.79% and 112. 00% in the human urine with RSDs lower than 9% (n= 5). The method proved precise, specific and reproducible, and can be used for the determination of the five components in urine.

  11. Evidence of interlipidic ion-pairing in anion-induced DNA release from cationic amphiphile-DNA complexes. Mechanistic implications in transfection.

    Bhattacharya, S; Mandal, S S


    Complex formation of DNA with a number of cationic amphiphiles has been examined using fluorescence, gel electrophoresis, and chemical nuclease digestion. Here we have addressed the status of both DNA and lipid upon complexation with each other. DNA upon binding with cationic amphiphiles changes its structure in such a way that it loses the ability to intercalate and becomes resistant to nuclease digestion. Fluorescence anisotropy measurements due to 1, 6-diphenylhexatriene (DPH) doped in cationic liposomes demonstrated that upon complexation with DNA, the resulting complexes still retain lamellar organizations with modest enhancement in thermal stabilities. The lipid-DNA complexation is most effective only when the complexation was carried out at or around the phase transition temperatures of the cationic lipid employed in the complexation with DNA. The release of DNA from cationic lipid-DNA complexes could be induced by several anionic additives. Determination of fluorescence anisotropies (due to DPH) as a function of temperature clearly demonstrates that the addition of equivalent amounts of anionic amphiphile into cationic lipid-DNA complexes leads to the ion-pairing of the amphiphiles, the melting profiles of which are virtually the same as those obtained in the absence of DNA. In this process DNA gets released from its complexes with cationic lipids and regains its natural intercalation ability, movement, and staining ability on agarose gel and also the sensitivities toward nuclease digestion. This clearly suggests that combination of ion-pairing and hydrophobic interactions between cationic and anionic amphiphiles is stronger than the electrostatic forces involved in the cationic lipid-DNA complexation. It is further revealed that the DNA release by anions is most efficient from the cationic lipid-DNA complexes at or around the Tm of the cationic lipid used in DNA complexation. This explains why more effective DNA delivery is achieved with cationic lipids

  12. Determination of risedronate in human urine by column-switching ion-pair high-performance liquid chromatography with ultraviolet detection.

    Vallano, P T; Shugarts, S B; Kline, W F; Woolf, E J; Matuszewski, B K


    An HPLC assay for the determination of risedronate in human urine was developed and validated. Risedronate and the internal standard were isolated from 5-ml urine samples in a two-part procedure. First, the analytes were precipitated from urine along with endogenous phosphates as calcium salts by the addition of CaCl(2) at alkaline pH. The precipitate was then dissolved in 0.05 M ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and subjected to ion-pair solid-phase extraction using a Waters HLB cartridge (1 ml, 30 mg) with 1-octyltriethylammonium phosphate as the ion-pair reagent. Following extraction, the analytes were initially separated from the majority of co-extracted endogenous components on a Waters X-Terra RP18 (4.6 x 50 mm, 3.5 microm) column. The effluent from the X-Terra was "heart-cut" onto a Phenomenex Synergi Polar RP (4.6 x 150 mm, 4 microm) column for final separation. UV detection (lambda=262 nm) was used to quantitate risedronate in the concentration range of 7.5-250 ng/ml. Mean recovery was 83.3% for risedronate and 86.5% for the internal standard. The intra-day precision of the assay, as assessed by replicate (n=5) standard curves, was better than 6% RSD for all points on the standard curve. Within-day accuracy for the standards ranged from 96.3 to 106.1% of nominal. Inter-day precision for quality controls assayed over a 3-week period was better than 5%, while inter-day accuracy was within 90% of nominal. The assay was employed to analyze samples collected during a clinical pharmacokinetics study.

  13. Target-guided separation of Bougainvillea glabra betacyanins by direct coupling of preparative ion-pair high-speed countercurrent chromatography and electrospray ionization mass-spectrometry.

    Jerz, Gerold; Wybraniec, Sławomir; Gebers, Nadine; Winterhalter, Peter


    In this study, preparative ion-pair high-speed countercurrent chromatography was directly coupled to an electrospray ionization mass-spectrometry device (IP-HSCCC/ESI-MS-MS) for target-guided fractionation of high molecular weight acyl-oligosaccharide linked betacyanins from purple bracts of Bougainvillea glabra (Nyctaginaceae). The direct identification of six principal acyl-oligosaccharide linked betacyanins in the mass range between m/z 859 and m/z 1359 was achieved by positive ESI-MS ionization and gave access to the genuine pigment profile already during the proceeding of the preparative separation. Inclusively, all MS/MS-fragmentation data were provided during the chromatographic run for a complete analysis of substitution pattern. On-line purity evaluation of the recovered fractions is of high value in target-guided screening procedures and for immediate decisions about suitable fractions used for further structural analysis. The applied preparative hyphenation was shown to be a versatile screening method for on-line monitoring of countercurrent chromatographic separations of polar crude pigment extracts and also traced some minor concentrated compounds. For the separation of 760mg crude pigment extract the biphasic solvent system tert.-butylmethylether/n-butanol/acetonitrile/water 2:2:1:5 (v/v/v/v) was used with addition of ion-pair forming reagent trifluoroacetic acid. The preparative HSCCC-eluate had to be modified by post-column addition of a make-up solvent stream containing formic acid to reduce ion-suppression caused by trifluoroacetic acid and later significantly maximized response of ESI-MS/MS detection of target substances. A variable low-pressure split-unit guided a micro-eluate to the ESI-MS-interface for sensitive and direct on-line detection, and the major volume of the effluent stream was directed to the fraction collector for preparative sample recovery. The applied make-up solvent mixture significantly improved smoothness of the continuously

  14. Experiments with Tris(ethylenediamine)cobalt(III) Compounds: 59Co NMR and the Resolution of Enantiomeric [Co(en)3] 3+ Ion and Analysis by Formation of Diastereomeric Ion Pairs

    Borer, L. L.; Russell, J. G.; Settlage, R. E.; Bryant, R. G.


    Cobalt(III) complexes have been used in the undergraduate inorganic laboratory to demonstrate various techniques in coordination chemistry. This report describes an experiment involving the synthesis and resolution of enantiomeric tris(ethylenediamine)cobalt(III) compounds followed by the analysis of enantiomeric purity by optical rotation and 59Co NMR spectroscopy through the formation of diastereomeric ion pairs.

  15. A quantitative approach to the determination of drug release from reverse-phase evaporation lipid vesicles. The influence of sodium ion-pair formation on warfarin partitioning and permeability

    Janssen, L.H.M.; Cools, A.A.


    The influence of sodium ion-pair formation on warfarin partitioning and permeability has been investigated using reverse-phase evaporation lipid vesicles. An experimental method for the isolation of the vesicles having known amounts of encapsulated drug has been described. The partitioning of warfar

  16. 离子对色谱分析测定双甘膦%Analysis of N-(Phosphonomethyl)iminodiacetic Acid by Ion-pair Chromatography

    刘奎涛; 王俊东


    采用离子对色谱法,以甲醇、水为流动相,C18反相硅胶柱和紫外检测器分离测定双甘膦.结果表明,双甘膦的标准偏差为0.003,变异系数为0.307%,平均回收率为98.96%,线性相关系数r2=0.999.%The quantitative analysis of mixture of N-(phosphonomethyl)iminodiacetic acid by ion-pair chromatography using methanol-water as mobile phase, C18 silica gel column and ultraviolet detector was described in this paper. The results showed that the standard deviation for N-(phosphonomethyl)iminodiacetic acid was 0.003, the coefficient of variation was 0.307%, the average recovery was 98.96%, and the linear correlation was 0.999.

  17. Spectrophotometric determination of low levels arsenic species in beverages after ion-pairing vortex-assisted cloud-point extraction with acridine red.

    Altunay, Nail; Gürkan, Ramazan; Kır, Ufuk


    A new, low-cost, micellar-sensitive and selective spectrophotometric method was developed for the determination of inorganic arsenic (As) species in beverage samples. Vortex-assisted cloud-point extraction (VA-CPE) was used for the efficient pre-concentration of As(V) in the selected samples. The method is based on selective and sensitive ion-pairing of As(V) with acridine red (ARH(+)) in the presence of pyrogallol and sequential extraction into the micellar phase of Triton X-45 at pH 6.0. Under the optimised conditions, the calibration curve was highly linear in the range of 0.8-280 µg l(-1) for As(V). The limits of detection and quantification of the method were 0.25 and 0.83 µg l(-1), respectively. The method was successfully applied to the determination of trace As in the pre-treated and digested samples under microwave and ultrasonic power. As(V) and total As levels in the samples were spectrophotometrically determined after pre-concentration with VA-CPE at 494 nm before and after oxidation with acidic KMnO4. The As(III) levels were calculated from the difference between As(V) and total As levels. The accuracy of the method was demonstrated by analysis of two certified reference materials (CRMs) where the measured values for As were statistically within the 95% confidence limit for the certified values.

  18. Simultaneous determination of arsenic and mercury species in rice by ion-pairing reversed phase chromatography with inductively coupled plasma mass spectrometry.

    Fang, Yong; Pan, Yushi; Li, Peng; Xue, Mei; Pei, Fei; Yang, Wenjian; Ma, Ning; Hu, Qiuhui


    An analytical method using reversed phase chromatography-inductively coupled plasma mass spectrometry for arsenic and mercury speciation analysis was described. The effect of ion-pairing reagent on simultaneous separation of four arsenic (arsenite, arsenate, monomethlyarsonate and dimethylarsinate) and three mercury species (inorganic mercury (Hg(II)), methylmecury and ethylmercury) was investigated. Parameters including concentrations and pH of the mobile phase were optimized. The separation and re-equilibration time was attained within 20min. Meanwhile, a sequential extraction method for arsenic and mercury in rice was tested. Subsequently, 1% HNO3 microwave-assisted extraction was chosen. Calibration curves based on peak area measurements were linear with correlation coefficient greater than 0.9958 for each species in the range studied. The detection limits of the species were in the range of 0.84-2.41μg/L for arsenic and 0.01-0.04μg/L for mercury, respectively. The proposed method was then successfully applied for the simultaneous determination of arsenic and mercury species in rice flour standard material and two kinds of rice from local markets.

  19. Efficient visible and near-infrared photoluminescent attapulgite-based lanthanide one-dimensional nanomaterials assembled by ion-pairing interactions.

    Xu, Jun; Zhang, Ye; Chen, Hao; Liu, Weisheng; Tang, Yu


    Attapulgite, a one-dimensional fibrillar nanomaterial present in nature, with its extreme stability, is a promising material to act as a new carrier of luminescent lanthanide complexes for further applications. Herein, a series of lanthanide complexes Na[Ln(TTA)4] have been attached to attapulgite (Atta) via ion-pairing interactions, generating the first example of attapulgite-based visible and near-infrared (NIR) luminescent lanthanide one-dimensional nanomaterials, where TTA is 2-thenoyltrifluoroacetonate and Ln is Eu, Sm, Nd, Er or Yb. The hybrid materials were characterized by CHN elemental analysis, inductively coupled plasma-atomic emission spectroscopy (ICP), powder X-ray diffraction (PXRD), thermogravimetry (TG), transmission electron microscopy (TEM), and UV-vis absorption spectra. In order to investigate the photophysical behaviours of these materials, the visible and NIR luminescent spectra and the energy transfer process have been systematically investigated. Moreover, efforts have been made to produce Eu- and Sm-based plastic attapulgite materials by utilizing poly(methyl methacrylate) (PMMA) matrices, and the dispersibility of the lanthanide-doped hybrids in PMMA provides them with a high mechanical strength. The lanthanide-doped attapulgite appears to be an interesting material for photophysical applications. The results of this work would have potential significance for the design and assembly of luminescent lanthanide materials for light-emitting diodes (LED), sunlight-conversion films, optical amplifiers, solar concentrators, and lasers.

  20. Development of an ion-pair reversed-phase HPLC method with indirect UV detection for determination of phosphates and phosphites as impurities in sodium risedronate.

    Breuzovska, Katerina; Dimitrovska, Aneta; Kitanovski, Zoran; Petrusevska, Jelena; Ribarska, Jasmina Tonic; Jolevska, Suzana Trajkovic


    A method based on RP-HPLC with indirect UV detection was developed for the determination of phosphates and phosphites as impurities in sodium risedronate. RP separation of the phosphates and phosphites was achieved by adding tetrabutylammonium hydroxide as an ion-pairing agent in the mobile phase. Potassium hydrogen phthalate was added to the mobile phase as an ionic chromophore in order to obtain high background absorption of the mobile phase. Separation was performed on a C18 column using a mixture of pH 8.2 buffer (containing 0.5 mM tetrabutylammonium hydroxide and 1 mM phthalate) and acetonitrile (95 + 5, v/v) as the mobile phase, with indirect UV detection at 248 nm. The validation of the method included determination of specificity/selectivity, linearity, LOD, LOQ, accuracy, precision, and robustness. The LOD was 0.86 microg/mL for phosphates and 0.76 microg/mL for phosphites. The LOQ was 2.60 microg/mL for phosphates and 2.29 microg/mL for phosphites. The developed method is suitable for quantitative determination of phosphates and phosphites as impurities in QC of sodium risedronate.

  1. Physicochemical studies on ion-pair amphiphiles: Solution and interfacial behaviour of systems derived from sodium dodecylsulfate and -alkyltrimethylammonium bromide homologues

    Kajari Maiti; Subhash C Bhattacharya; Satya P Moulik; Amiya K Panda


    Bulk and interfacial properties of ion-pair amphiphiles (IPA), formed between sodium dodecylsulfate (SDS) and -alkyltrimethylammonium bromide homologues (CTAB; = 10, 12, 14, 16, and 18), have been investigated. Different phases and aggregated states, formed in the ternary combinations of CTAB/SDS/H2O, have been identified and described. Equimolar mixture of IPAs in water yielded precipitates, in the form of coacervates. Aqueous solubility of isolated coacervates in presence and absence of additives like cholesterol and bile salts have been examined. The isolated coacervates have been characterized by 1H NMR, FTIR, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarization microscopic measurements. The coacervates have appeared in the shape of needle and complex flower-like aggregates. Surface pressure ()-area (A) isotherm of the coacervates at the air/water interface have been constructed and compared with the lipid 1,2-dipalmitoyl--glycero-3-phosphocholine (DPPC). Morphologies of the IPA monolayers at different surface pressures have been also examined by epifluorescence microscopy. The compressed interfacial monolayers have produced spherical (both regular and irregular) and fern-leaf like domains.

  2. Development of an Ion-Pairing Reagent and HPLC-UV Method for the Detection and Quantification of Six Water-Soluble Vitamins in Animal Feed

    Ho Jin Kim


    Full Text Available A novel and simple method for detecting six water-soluble vitamins in animal feed using high performance liquid chromatography equipped with a photodiode array detector (HPLC/PDA and ion-pairing reagent was developed. The chromatographic peaks of the six water-soluble vitamins were successfully identified by comparing their retention times and UV spectra with reference standards. The mobile phase was composed of buffers A (5 mM PICB-6 in 0.1% CH3COOH and B (5 mM PICB-6 in 65% methanol. All peaks were detected using a wavelength of 270 nm. Method validation was performed in terms of linearity, sensitivity, selectivity, accuracy, and precision. The limits of detection (LODs for the instrument employed in these experiments ranged from 25 to 197 μg/kg, and the limits of quantification (LOQs ranged from 84 to 658 μg/kg. Average recoveries of the six water-soluble vitamins ranged from 82.3% to 98.9%. Method replication resulted in intraday and interday peak area variation of <5.6%. The developed method was specific and reliable and is therefore suitable for the routine analysis of water-soluble vitamins in animal feed.

  3. Aspects on the catalysis of lipase from porcine pancreas (type VI-s in aqueous media: development of ion-pairs

    Marina Kokkinou


    Full Text Available This article reports a first contribution for the elucidation of catalytic mechanism of Lipase from porcine pancreas, type VI-s (PPL, in hydrolyzing an ester substrate in aqueous media. The conclusions were based on the pH-profiles of Michaelis-Menten parameters k cat/Km, k cat and Km, as well as on the absolute temperature profile of k cat/Km, obtained during the hydrolysis of p-nitrophenyl laurate by PPL. It was found that (a PPL performs catalysis by means of ion pairs formed either as Ser152-Ο-/His263-Im+H and/or Carbonyl-Ο-/His263-Im+H, (b the parameter k cat/Km equals to k1 and thus ES is formed and destroyed in the course of a series of consecutive reactions governed by the dynamic constant K S = k2/k1, and (c the hydrolysis of substrate is assisted by a hydrogen bond developed between deprotonated Asp176 and the positively charged imidazole of His263 across a pKa-value 3.85, necessary for efficient catalysis.

  4. Ion-pair chromatography coupled to inductively coupled plasma-mass spectrometry (IPC-ICP-MS) as a method for thiomolybdate speciation in natural waters.

    Lohmayer, Regina; Reithmaier, Gloria Maria Susanne; Bura-Nakić, Elvira; Planer-Friedrich, Britta


    Molybdenum precipitates preferentially under reducing conditions; therefore, its occurrence in sediment records is used as an indicator of paleoredox conditions. Although thiomolybdates (MoO4-xSx(2-) with x = 1-4) supposedly are necessary intermediates in the process of molybdenum precipitation under anoxic conditions, there is no information about their abundance in natural environments, because of a lack of element-specific methods with sufficiently low detection limits. Here, we optimized ion-pair chromatographic separation for coupling to an inductively coupled plasma-mass spectrometry detector (IPC-ICP-MS). 2-Propanol (10%-25% gradient) replaced the previously used acetonitrile (25%-75%) as the solvent, to reduce the carbon load into the plasma. In synthetic solutions, formation of thiomolybdates was found to occur spontaneously in the presence of excess sulfide and the degree of thiolation was highest at pH 7. Excess hydroxyl led to a transformation of thiomolybdates to molybdate. Under acidic to neutral conditions, precipitation of molybdenum and hydrolysis of tetrathiomolybdate were observed. Flash-freezing was found to be suitable to stabilize tetrathiomolybdate, with 2 mM) negatively affected the detection of molybdate, which eluted mainly in the dead volume, but had no negative effect on higher thiolated molybdates. Detection limits were ∼10 nM. With the newly developed IPC-ICP-MS method, thiomolybdates were found to form spontaneously in euxinic marine waters after adding a molybdate spike and occur naturally in sulfidic geothermal waters.

  5. Quantitative analysis of metabolites in complex biological samples using ion-pair reversed-phase liquid chromatography-isotope dilution tandem mass spectrometry.

    Seifar, Reza M; Zhao, Zheng; van Dam, Jan; van Winden, Wouter; van Gulik, Walter; Heijnen, Joseph J


    A rapid, sensitive and selective ion-pair reversed-phase liquid chromatography-electrospray ionization isotope dilution tandem mass spectrometry (IP-LC-ESI-ID-MS/MS) was developed for quantitative analysis of free intracellular metabolites in cell cultures. As an application a group of compounds involved in penicillin biosynthesis pathway of Penicillium chrysogenum cells, such as penicillin G (PenG), 6-aminopenicillanic acid (6-APA), benzylpenicilloic acid (PIO), ortho-hydroxyphenyl acetic acid (o-OH-PAA), phenylacetic acid (PAA), 6-oxopipeidine-2-carboxylic acid (OPC), 8-hydroxypenicillic acid (8-HPA), L-alpha-(delta-aminoadipyl)-L-alpha-cystenyl-D-alpha-valine (ACV) and isopenicillin N (IPN) were chosen. (13)C-labeled analogs of the metabolites were added to the sample solutions as internal standards (I.S.). Sample mixtures were analyzed without any sample pretreatment. No extraction recovery check was needed because I.S. was added to the cell samples before extraction process. The method showed excellent precision (relative standard deviation (RSD)

  6. Simultaneous determination of pyridoxine hydrochloride and doxylamine succinate from tablets by ion pair reversed-phase high-performance liquid chromatography (RP-HPLC).

    Argekar, A P; Sawant, J G


    A new, simple, precise, and rapid ion pair reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed for the simultaneous determination of pyridoxine hydrochloride (PYR) and doxylamine succinate (DOX) in tablets. The stationary phase was a Microbondapak C18 column (10 mu, 300 mm x 3.9 mm i.d.). The mobile phase was water:methanol (60:40) containing 10 mM heptanesulfonic acid and 0.25% triethylamine and adjusted to pH 2.2 with orthophosphoric acid. Detection was carried out at 263 nm using an ultraviolet (UV) detector. The flow rate was 1.0 ml/min, and retention times were 3.65 min and 7.32 min for PYR and DOX, respectively. The linearity was obtained in the concentration range 0.5-500 micrograms/ml for PYR and DOX. Mean percentage recoveries were 100.20% and 101.20% for PYR and DOX, respectively.

  7. Synthesis and Structure of a Novel Ion-pair Palladium(Ⅱ) Compound Containing 2-Thioxo-1,3-dithiole-4,5-bis(thiolate)


    A novel ion-pair palladium(Ⅱ) compound, (NO2BzPy)2[Pd(dmit)2] (NO2BzPy+ = 1-(4-nitrobenzyl)pyridinium, dmit2- = 2-thioxo-1,3-dithiole-4,5-bis(thiolate)), was synthesized and characterized by single-crystal X-ray structure determination. This compound crystallizes in the monoclinic system, space group P21/n with a = 10.4463(11), b = 8.5627(9), c = 20.017(2) (A), β = 97.7730(10)°, V = 1774.1(3) (A)3, Z = 2, C30H22N4O4S10Pd, Mr = 929.52, Dc = 1.740 g/cm3, μ = 1.155 mm-1, S = 1.006, F(000) = 936, R = 0.0354 and wR = 0.0675. The most intriguing general structural feature of the compound is the completely segregated columnar stacks of anions and cations. There exist hydrogen-bonding interactions within the cation column.

  8. Elution behavior of short dsDNA strands in silicon micropillar array columns in ion pair reversed-phase chromatography mode.

    Zhang, Lei; Majeed, Bivragh; Lynen, Frederic; Van Hoof, Chris; De Malsche, Wim


    In the present paper, dsDNA separation has been studied in a silicon micropillar array column using ion-pair RP-HPLC (IP-RP-HPLC). The deep-etched (32.0 μm) silicon micropillar array was fabricated by advanced deep UV lithography and by a dedicated Bosch etch process and then sealed by anodic bonding to a Pyrex glass. The pillar surface was subsequently conditioned hydrophobic. Working in isocratic mode under nonretained conditions, van Deemter curves of dsDNA and coumarin were established to assess the performance of the micropillar array column, resulting in plate heights of only a few micrometers. Working in gradient mode, separations of dsDNA fragments were evaluated. The relevant gradient operation parameters were studied to understand their influence on dsDNA separations. The correlation between DNA length and retention was measured and theoretically described in a length range of 50-500 bp, promising for the determination of DNA of an unknown length. Finally, a separation example demonstrated the excellent separation power of on-chip IP-RP chromatography by achieving a large operation range of DNA length (10-300 bp) with a 5-bp difference among 11 dsDNA fragments. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Application of a cholesterol stationary phase in the analysis of phosphorothioate oligonucleotides by means of ion pair chromatography coupled with tandem mass spectrometry.

    Studzińska, Sylwia; Krzemińska, Katarzyna; Szumski, Michał; Buszewski, Bogusław


    The main aim of this study was the investigation of the influence of several ion pair reagents towards both the retention and the mass spectrometry sensitivity of phosphorothioate oligonucleotides. A cholesterol stationary phase was applied for the first time in the analysis of this group of compounds. The mobile phase composition was modified by changing the concentration and the type of amines and acetates or 1,1,1,3,3,3-hexafluoroisopropanol. It has been shown that the increase of amines concentration results in the retention factor increase for each oligonucleotide, on each adsorbent. The only exception was the mobile phase composed of triethylamine and 1,1,1,3,3,3-hexafluoroisopropanol. This is a consequence of interactions taking place between a cholesterol molecule and an alcohol. This effect was convenient when the mass spectrometry detection was applied, since it allowed an increase in the sensitivity. Moreover, optimization of the mobile phase composition and its impact on the efficiency of ionization process and on the sensitivity in mass spectrometry were also presented. The optimization of this new method, based on cholesterol stationary phase coupled with mass spectrometry detection, was finally applied for the determination of phosphorothioate oligonucleotides impurity in a real sample. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Development and validation of an ion-pair chromatographic method for simultaneous determination of trans- and cis-urocanic acid in fish samples.

    Zare, Davood; Muhammad, Kharidah; Bejo, Mohd Hair Bin; Ghazali, Hasanah Mohd


    Urocanic acid (UCA) has been reported to be a mast cell degranulator and has also been suggested as a complementary agent in implicated scombroid fish poisoning. In this research, a new method is described to extract, clean up and perform simultaneous ion-pair chromatographic analysis of trans- and cis-urocanic acid (UCA) in fish samples. UCA was extracted using 0.05 M HCl and protein was removed from the extract by precipitation with 10% trisodium citrate and 10% citric acid. The HPLC method that is developed showed a rapid, precise and sensitive method with short retention time for simultaneous separation of UCA isomers in fish samples. Estimation of trans- and cis-UCA in the muscle of Indian mackerel, tuna and sardine showed that, as expected, no cis-UCA existed in fish muscles and the highest concentration of trans-UCA was found in Indian mackerel with 118.8 mg kg(-1) while the highest concentrations of trans-UCA in tuna and sardine were 12.1 and 17.5 mg kg(-1), respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Spectrophotometric determination of some anti-tussive and anti-spasmodic drugs through ion-pair complex formation with thiocyanate and cobalt(II) or molybdenum(V)

    El-Shiekh, Ragaa; Zahran, Faten; El-Fetouh Gouda, Ayman Abou


    Two rapid, simple and sensitive extractive specrophotometric methods has been developed for the determination of anti-tussive drugs, e.g., dextromethorphan hydrobromide (DEX) and pipazethate hydrochloride (PiCl) and anti-spasmodic drugs, e.g., drotaverine hydrochloride (DvCl) and trimebutine maleate (TM) in bulk and in their pharmaceutical formulations. The proposed methods depend upon the reaction of cobalt(II)-thiocyanate (method A) and molybdenum(V)-thiocyanate ions (method B) with the cited drugs to form stable ion-pair complexes which extractable with an n-butnol-dichloromethane solvent mixture (3.5:6.5) and methylene chloride for methods A and B, respectively. The blue and orange red color complexes are determined either colorimetrically at λmax 625 nm (using method A) and 467 or 470 nm for (DEX and PiCl) or (DvCl and TM), respectively (using method B). The concentration range is 20-400 and 2.5-50 μg mL -1 for methods A and B, respectively. The proposed method was successfully applied for the determination of the studied drugs in pure and in pharmaceutical formulations applying the standard additions technique and the results obtained in good agreement well with those obtained by the official method.

  12. Development and validation of a reversed-phase ion-pair high-performance liquid chromatographic method for the determination of risedronate in pharmaceutical preparations.

    Kyriakides, Demetra; Panderi, Irene


    A stability indicating, reversed-phase ion-pair high-performance liquid chromatographic method was developed and validated for the determination of risedronate in pharmaceutical dosage forms. The determination was performed on a BDS C(18) analytical column (250 mm x 4.6 mm i.d., 5 microm particle size); the mobile phase consisted of 0.005 M tetrabutylammonium hydroxide and 0.005 M pyrophosphate sodium (pH 7.0) mixed with acetonitrile in a ratio (78:22, v/v) and pumped at a flow rate 1.00 mL min(-1). The ultraviolet (UV) detector was operated at 262 nm. The retention times of magnesium ascorbyl phosphate, which was used as internal standard and risedronate were 4.94 and 5.95 min, respectively. The calibration graph was ranged from 2.50 to 20.00 microg mL(-1), while detection and quantitation limits were found to be 0.48 and 1.61 microg mL(-1), respectively. The intra- and inter-day percentage relative standard deviations, %R.S.D., were less than 5.9%, while the relative percentage error, %E(r), was less than 0.4%. The method was applied to the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control.

  13. Rapid and effective synthesis of $\\text{}^{40}\\text{Ca}-\\text{}^{27}\\text{Al}$ ion pair towards quantum logic optical clock

    Shang, Junjuan; Cao, Jian; Wang, Shaomao; Shu, Hualin; Huang, Xueren


    High precision atomic clocks have been applied not only to very important technological problems such as synchronization and global navigation systems, but to the fundament precision measurement physics. Single $\\text{}^{27}\\text{Al}^+$ is one of the most attractions of selection system due to its very low blackbody radiation effect which dominates frequency shifts in other optical clock systems. Up to now, the $\\text{}^{27}\\text{Al}^+$ still could not be laser-cooled directly by reason that the absence of 167nm laser. Sympathetic cooling is a viable method to solve this problem. In this work, we used a single laser cooled $\\text{}^{40}\\text{Ca}^+$ to sympathetically cool one $\\text{}^{27}\\text{Al}^+$ in linear Paul trap. Comparing to laser ablation method we got a much lower velocity atoms sprayed from a home-made atom oven, which would make loading aluminum ion more efficient and the sympathetic cooling much easier. By the method of precisely measuring the secular frequency of the ion pair, finally we prove...

  14. Development and validation of an ion-pair liquid chromatographic method for the quantitation of sodium cromoglycate in urine following inhalation.

    Aswania, O A; Corlett, S A; Chrystyn, H


    An ion-pair liquid high-performance chromatography method with solid-phase extraction for measuring urinary concentrations of sodium cromoglycate following inhalation has been developed and validated. Sodium cromoglycate was extracted from urine on a 100-mg phenyl cartridge (Isolute, Jones Chromatography) and then quantified on a 25-cm C8 Spherisorb 5 microns stationary phase with a mobile phase of methanol-0.045 M phosphate buffer-0.05 M dodecyl triethyl ammonium phosphate (550:447.6:2.4, v/v) pH 2.3, at 0.85 ml min-1 using nedocromil sodium as an internal standard and UV detection at 238 nm. The inter- and intra-day reproducibilities were 8.33 and 13.63%, respectively, at 0.25 mg l-1. The limit of determination for sodium cromoglycate was 0.25 mg l-1 (with a signal-to-noise ratio of greater than 10:1). Following oral and inhaled administration of 20 mg of sodium cromoglycate to eight healthy volunteers, the mean and S.D. of sodium cromoglycate excreted in the urine at 0.5, 1 and 24 h post-dose were 0.02, 0.05 and 0.33%, and 0.16, 0.30 and 1.55% of the dose, respectively. The urinary recovery of sodium cromoglycate at 0.5 and 1 h following inhalation can therefore be used to compare the amount of drug reaching the respiratory tract using different sodium cromoglycate inhaled products or inhalation methods.

  15. A novel ion-pairing chromatographic method for the simultaneous determination of both nicarbazin components in feed additives: chemometric tools for improving the optimization and validation.

    De Zan, María M; Teglia, Carla M; Robles, Juan C; Goicoechea, Héctor C


    The development, optimization and validation of an ion-pairing high performance liquid chromatography method for the simultaneous determination of both nicarbazin (NIC) components: 4,4'-dinitrocarbanilide (DNC) and 2-hydroxy-4,6-dimethylpyrimidine (HDP) in bulk materials and feed additives are described. An experimental design was used for the optimization of the chromatographic system. Four variables, including mobile phase composition and oven temperature, were analyzed through a central composite design exploring their contribution to analyte separation. Five responses: peak resolutions, HDP capacity factor, HDP tailing and analysis time, were modelled by using the response surface methodology and were optimized simultaneously by implementing the desirability function. The optimum conditions resulted in a mobile phase consisting of 10.0 mmol L(-1) of 1-heptanesulfonate, 20.0 mmol L(-1) of sodium acetate, pH=3.30 buffer and acetonitrile in a gradient system at a flow rate of 1.00 mL min(-1). Column was an INERSTIL ODS-3 (4.6 mm×150 mm, 5 μm particle size) at 40.0°C. Detection was performed at 300 nm by a diode array detector. The validation results of the method indicated a high selectivity and good precision characteristics, with RSD less than 1.0% for both components, both in intra and inter-assay precision studies. Linearity was proved for a range of 32.0-50.0 μg mL(-1) of NIC in sample solution. The recovery, studied at three different fortification levels, varied from 98.0 to 101.4 for HDP and from 99.1 to 100.2 for DNC. The applicability of the method was demonstrated by determining DNC and HDP content in raw materials and commercial formulations used for coccidiosis prevention. Assays results on real samples showed that considerable differences in molecular ratio DNC:HDP exist among them.

  16. Preparation and evaluation of packed capillary columns for the separation of nucleic acids by ion-pair reversed-phase high-performance liquid chromatography.

    Oberacher, H; Krajete, A; Parson, W; Huber, C G


    Oligonucleotides and double stranded DNA fragments were separated in 200 microm I.D. capillary columns packed with micropellicular, octadecylated, 2.1 microm poly(styrene-divinylbenzene) particles by ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC). Both the length and the diameter of the connecting capillaries (150 x 0.020 mm I.D.) as well as the detection volume (3 nl) had to be kept to a minimum in order to maintain the high efficiency of this chromatographic separation system with peak widths at half height in the range of a few seconds. Three different types of frits, namely sintered silica particles, sintered octadecylsilica particles, and monolithic poly(styrene-divinylbenzene) (PS-DVB) frits were evaluated with respect to their influence on chromatographic performance. Best performance for the separation of oligonucleotides and long DNA fragments was observed with the PS-DVB frits, whereas the short DNA fragments were optimally resolved in columns terminated by octadecylsilica frits. The maximum loading capacity of 60 x 0.20 mm I.D. columns ranged from 20 fmol (7.7 ng) for a 587 base pair DNA fragment to 500 fmol (2.4 ng) for a 16-mer oligonucleotide. Lower mass- and concentration detection limits in the low femtomol and low nanomol per liter range, respectively, make capillary IP-RP-HPLC with UV absorbance detection highly attractive for the separation and characterization of minute amounts of synthetic oligonucleotides, DNA restriction fragments, and short tandem repeat sequences amplified by polymerase chain reaction.

  17. Ionisation and dissociation of diarylmethyl chlorides in BCl/sub 3/CH/sub 2/Cl/sub 2/ solution: Spectroscopic evidence for carbenium ion pairs

    Schneider, R.; Mayr, H.; Plesch, P.H.


    The ionisation equilibria of diarylmethyl chlorides Ar/sub 2/CHCl (Ar = p-CH/sub 3/O-C/sub 6/H/sub 4/, p-PhO-C/sub 6/H/sub 4/, p-CH/sub 3/-C/sub 6/H/sub 4/) reacting with BCl/sub 3/ in CH/sub 2/Cl/sub 2/ to give ion-pairs Ar/sub 2/CH/sup +/BCl/sub 4//sup -/ (K/sub 1/), and the dissociation of these (K/sub D/) were studied by conductimetry and spectro-photometry. The molar conductivities are almost independent of the nature of the aryl group (approx. = 3.5.10/sup -3/ Sm/sup 2/mol at -70/sup 0/C). The ionisation constants K/sub I/ increase strongly with increasing electron releasing ability of the p-substituents. The standard ionisation enthalpies and entropies for (p-CH/sub 3/-C/sub 6/H/sub 4/)/sub 2/CHCl and (p-PhO-C/sub 6/H/sub 4/)(Ph)CHCl, calculated from the K/sub I/ at different temperatures are negative. The dissociation constants K/sub D/ ((1.9-2.9).10/sup -4/ molL at -70/sup 0/C) do not show a systematic dependence on the electron donating abilities of the substituents in the aryl groups. Small differences between the UV-vis absorption spectra of unpaired and paired ions were used to confirm the conductimetrically determined values of K/sub D/.

  18. A novel solid-phase extraction for the concentration of sweeteners in water and analysis by ion-pair liquid chromatography-triple quadrupole mass spectrometry.

    Gan, Zhiwei; Sun, Hongwen; Wang, Ruonan; Feng, Biting


    A highly sensitive method for the simultaneous trace (ng/L) quantification of seven commonly used artificial sweeteners in a variety of water samples using solid-phase extraction and ion-pair high-performance liquid chromatography (HPLC) triple quadrupole mass spectrometer with an electrospray ionization source (ESI-MS) in negative ion multiple reaction monitoring mode was developed. Ten solid phase extraction (SPE) cartridges were tested to evaluate their applicability for the pre-concentration of the analytes, and their loading and eluting parameters were optimized. Satisfactory recoveries (77-99%) of all of the studied sweeteners were obtained using a Poly-Sery PWAX cartridge with 25 mM sodium acetate solution (pH 4) as wash buffer and methanol containing 1mM tris (hydroxymethyl) amino methane (TRIS) as eluent. The method is sound and does not require pH adjustment or buffering of water samples. The HPLC separation was performed on an Athena C18-WP column with water and acetonitrile, both containing 5mM ammonium acetate and 1mM TRIS as mobile phases, in gradient elution mode. The linearity, precision, and accuracy of the method were evaluated, and good reproducibility was obtained. Method quantification limits varied between 0.4 and 7.5 ng/L for different water samples. The post-extraction spike method was applied to assess matrix effects, and quantification was achieved using internal standard calibration to overcome the unavoidable matrix effects during ESI-MS analysis. The method was applied to the analysis of thirteen water samples from Tianjin, China, including wastewater, tap water, surface water, and groundwater. The method described here is time-saving, accurate and precise, and is suitable for monitoring artificial sweeteners in different water matrices.

  19. Measurement of NMDA Receptor Antagonist, CPP, in Mouse Plasma and Brain Tissue Following Systematic Administration Using Ion-Pair LCMS/MS.

    Gemperline, Erin; Laha, Kurt; Scarlett, Cameron O; Pearce, Robert A; Li, Lingjun


    (RS)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) is a competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor and is routinely used with rodent models to investigate the role of NMDA receptors in brain function. This highly polar compound is difficult to separate from biological matrices. A reliable and sensitive assay was developed for the determination of CPP in plasma and tissue. In order to overcome the challenges relating to the physicochemical properties of CPP we employed an initial separation using solid phase extraction harnessing mixed-mode anion exchange. Then an ion-pair UPLC C18 separation was performed followed by MS/MS with a Waters Acquity UPLC interfaced to an AB Sciex QTrap 5500 mass spectrometer, which was operated in positive ion ESI mode. Multiple reaction monitoring (MRM) mode was utilized to detect the analyte and internal standard. The precursor to product ions used for quantitation for CPP and internal standard were m/z 252.958 → 207.100 and 334.955 → 136.033, respectively. This method was applied to a pharmacokinetic study and examined brain tissue and plasma concentrations following intravenous and intraperitoneal injections of CPP. The elimination half-life (t1/2) of CPP was 8.8 minutes in plasma and 14.3 minutes in brain tissue, and the plasma to brain concentration ratio was about 18:1. This pharmacokinetic data will aid the interpretation of the vast number of studies using CPP to investigate NMDA receptor function in rodents and the method itself can be used to study many other highly polar analytes of interest.

  20. The next generation of DNA profiling--STR typing by multiplexed PCR--ion-pair RP LC-ESI time-of-flight MS.

    Pitterl, Florian; Niederstätter, Harald; Huber, Gabriela; Zimmermann, Bettina; Oberacher, Herbert; Parson, Walther


    For the first time a multiplexed PCR approach suitable for mass spectrometric STR allele identification is presented. Thirteen forensically important STR markers (vWA, D21S11, D3S1358, D16S539, D8S1179, D7S820, D13S317, D5S818, TPOX, CSF1PO, D2S441, D10S1248, and D22S1045) and the gender typing locus amelogenin were simultaneously amplified. Ion-pair reversed-phase high-performance liquid chromatography electrospray-ionization time-of-flight mass spectrometry (ICEMS) was applied for genotyping, and allowed for highly efficient characterization of multiple PCR amplicons. Compared with electrophoretic sizing ICEMS enabled for the simultaneous detection of length and nucleotide variations. Thus, the obtained amount of biological information present within STR profiles was significantly increased even though the compatibility of typing results with electrophoretically generated data(bases) was maintained. Other advantages of the ICEMS platform included the abandonment of internal size standards, allelic ladders, and any kind of spectral calibration. The 14-plex PCR was tailor-made for ICEMS analysis by designing primer pairs that bind close to the repeat region, by using a proof reading polymerase for amplification, and by implementing molecular mass modifiers for prevention of molecular mass overlaps. In a series of experiments, the performance of the multiplexed PCR-ICEMS assay was evaluated. The ICEMS-based DNA profiling assay was found to be competitive regarding detection sensitivity and analyzability of degraded and casework samples with commercially available electrophoretic typing approaches, which suggests that multiplexed PCR-ICEMS assays could represent a valuable tool for (forensic) genetics.

  1. Three ion-pair complexes containing bis(maleonitriledithiolate)copper(II) anion and substituted 2-aminopyridinium cations: Syntheses, crystal structures, and magnetic properties

    Liu, Yin; Ou, Shu-Hua; Li, Jin-Ni; Liao, Xiao-Lan; Zheng, Xiao-Xu; Luo, Cui-Ping; Yang, Le-Min; Zhou, Jia-Rong; Ni, Chun-Lin


    Three new ion-pair complexes, [2-ClBz-2‧-NH2Py]2[Cu(mnt)2](1), [2-Cl-4-ClBz-2-NH2Py]2[Cu(mnt)2](2) and [2-Cl-4-BrBz-2‧-NH2Py]2[Cu(mnt)2]·C2H5OH(3) ([2-Cl-4-RBz-2‧-NH2Py]+ = 1-(2‧-chloro-4‧-Rbenzyl)-2-aminopyridinium, R = H, Cl, Br; mnt2- = maleonitriledithiolate), were synthesized and characterized by elemental analyses, IR, UV-visible, single crystal X-ray diffraction and magnetic measurements. Both 1 and 2 crystallize in the monoclinic space group P2(1)/c, and the [Cu(mnt)2]2- anions and the cations form a 1D network structure through the N-HṡṡṡN hydrogen bonds. While the anions in 3 form a ladder-like chain through the C-HṡṡṡN interactions between the [Cu(mnt)2]2- anions and CH3CH2OH molecules. Some weak interactions such as πṡṡṡπ, CuṡṡṡN, ClṡṡṡC, and C-HṡṡṡCl, O-HṡṡṡCl, C-HṡṡṡS, N-HṡṡṡO, N-HṡṡṡN and C-HṡṡṡN hydrogen bonds in three molecular solids generate further a 3D network structure. The magnetic measurement reveals that 1 shows a very weak ferromagnetic interaction, and 2 exhibits a transition from ferromagnetic to antiferromagnetic coupling about 15 K, while 3 shows an antiferromagnetic coupling feature with θ = -12.51 K when the temperature is lowered.

  2. Determination of melamine in milk-based products and other food and beverage products by ion-pair liquid chromatography-tandem mass spectrometry

    Ibanez, Maria; Sancho, Juan V. [Research Institute for Pesticides and Water, University Jaume I, E-12071, Castellon (Spain); Hernandez, Felix, E-mail: [Research Institute for Pesticides and Water, University Jaume I, E-12071, Castellon (Spain)


    This paper describes a fast method for the sensitive and selective determination of melamine in a wide range of food matrices, including several milk-based products. The method involves an extraction with aqueous 1% trichloroacetic acid before the injection of the 10-fold diluted extract into the liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) system, using labelled melamine as the internal standard. As melamine is present in aqueous media in the cationic form, the chromatographic separation in reversed-phase LC requires the use of anionic ion-pair reagents, such as tridecafluoroheptanoic acid (THFA). This allows a satisfactory chromatographic retention and peak shape in all the types of food samples investigated. The method has been validated in six food matrices (biscuit, dry pasta and four milk-based products) by means of recovery experiments in samples spiked at 1 and 5 mg kg{sup -1}. Average recoveries (n = 5) ranged from 77% to 100%, with excellent precision (RSDs lower than 5%) and limits of detection between 0.01 and 0.1 mg kg{sup -1}. In addition, accuracy and robustness of the method was proven in different soya-based matrices by means of quality control (QC) sample analysis. QC recoveries, at 1 and 2.5 mg kg{sup -1}, were satisfactory, ranging from 79% to 110%. The method developed in this work has been applied to the determination of melamine in different types of food samples. All detections were confirmed by acquiring two MS/MS transitions (127 > 85 for quantification; 127 > 68 for confirmation) and comparing their ion intensity ratio with that of reference standards. Accuracy of the method was also assessed by applying it to a milk-based product and a baking mix material as part of an EU proficiency test, in which highly satisfactory results were obtained.

  3. Simultaneous quantification of amino acids and Amadori products in foods through ion-pairing liquid chromatography-high-resolution mass spectrometry.

    Troise, Antonio Dario; Fiore, Alberto; Roviello, Giovanni; Monti, Simona Maria; Fogliano, Vincenzo


    The formation of the Amadori products (APs) is the first key step of Maillard reaction. Only few papers have dealt with simultaneous quantitation of amino acids and corresponding APs (1-amino-1-deoxy-2-ketose). Chromatographic separation of APs is affected by several drawbacks mainly related to their poor retention in conventional reversed phase separation. In this paper, a method for the simultaneous quantification of amino acids and their respective APs was developed combining high-resolution mass spectrometry with ion-pairing liquid chromatography. The limit of detection was 0.1 ng/mL for tryptophan, valine and arginine, while the limit of quantification ranged from 2 to 5 ng/mL according to the specific sensitivity of each analyte. The relative standard deviation % was lower than 10 % and the coefficient of correlation was higher than 0.99 for each calibration curve. The method was applied to milk, milk-based products, raw and processed tomato. Among the analyzed products, the most abundant amino acid was glutamic acid (16,646.89 ± 1,385.40 µg/g) and the most abundant AP was fructosyl-arginine in tomato puree (774.82 ± 10.01 µg/g). The easiness of sample preparation coupled to the analytical performances of the proposed method introduced the possibility to use the pattern of free amino acids and corresponding APs in the evaluation of the quality of raw food as well as the extent of thermal treatments in different food products.

  4. Contact dermatitis

    Dermatitis - contact; Allergic dermatitis; Dermatitis - allergic; Irritant contact dermatitis; Skin rash - contact dermatitis ... There are 2 types of contact dermatitis. Irritant dermatitis: This ... with acids, alkaline materials such as soaps and detergents , ...

  5. Separation of intermediates of iron-catalyzed dopamine oxidation reactions using reversed-phase ion-pairing chromatography coupled in tandem with UV-visible and ESI-MS detections.

    Zhang, Lin; Yagnik, Gargey; Jiang, Dianlu; Shi, Shuyun; Chang, Peter; Zhou, Feimeng


    Reversed-phase ion-pairing chromatography (RP-IPC) is coupled on-line with electrospray ionization-mass spectrometry (ESI-MS) through an interface comprising a four-way switch valve and an anion exchange column. Regeneration of the anion exchange column can be accomplished on-line by switching the four-way switch valve to interconnect the column to a regeneration solution. Positioning the anion exchange column between the RP-IPC and ESI-MS instruments allows the ion-pairing reagent (IPR) sodium octane sulfonate to be removed. The IPC-ESI-MS method enabled us to separate and detect four intermediates of the Fe(III)-catalyzed dopamine oxidation. In particular, 6-hydroxydopamine, which is short-lived and highly neurotoxic, was detected and quantified. Together with the separation of other intermediates, gaining insight into the mechanism and kinetics of the Fe(III)-catalyzed dopamine oxidation becomes possible.

  6. Raman and DFT Study on N-H+…Cl- Hydrogen Bonding in 1,1,3,3-Tetra-Methylguanidinium Chloride forming an Ion-pair Molecule in the Vapor Phase

    Berg, Rolf W.; Riisager, Anders; Fehrmann, Rasmus

    The chemistry of 1,1,3,3-tetramethylguanidinium ([TMGH]+) chloride, a low temperature (molten) ionic liquid, is discussed, based on its Raman spectra associated with ab initio molecular orbital DFT-type quantum mechanical calculations (with 6-311+G(d,p) basis sets) on “molecules” in isolated...... that dimeric molecular ion pairs with four N-H+…Cl- hydrogen bonds seem to exist also in the solutions, and probably are responsible for the relatively high solubility of the “salt” in ethanol. The “salt” can be easily sublimed at about 200-230 oC. The Raman spectrum of the vapor at 225 ºC has a characteristic...... strong band at 2229 cm-1 that shows that the gas phase consists of monomeric ion pair “molecules” (Fig.2) held together by one N-H+…Cl- hydrogen bond, the stretching band of which is causing the band (Fig.3)....

  7. Ion-pair triple helicates and mesocates self-assembled from ditopic 2,2 -bipyridine-bis(urea) ligands and Ni(II) and Fe(II) sulfate salts

    Custelcean, Radu [ORNL; Bonnesen, Peter V [ORNL; Roach, Benjamin D [ORNL; Duncan, Nathan C [ORNL


    NiSO{sub 4} and FeSO{sub 4} self-assemble with heteroditopic ligands (L) comprising 2,2{prime}-bipyridine and o-phenylene-(bis)urea cation- and anion-binding sites, respectively, into [ML{sub 3}SO{sub 4}] (M = Ni{sup 2+}, Fe{sup 2+}) triple-stranded ion-pair helicates and mesocates.

  8. Development of a drug-in-adhesive patch combining ion pair and chemical enhancer strategy for transdermal delivery of zaltoprofen: pharmacokinetic, pharmacodynamic and in vitro/in vivo correlation evaluation.

    Cui, Hongxia; Quan, Peng; Zhou, Zhuang; Fang, Liang


    The aim of the study was to develop a drug-in-adhesive patch system for transdermal delivery of zaltoprofen (ZAL). The formulation was designed in combination with the ion pair and chemical enhancer strategy. Seven organic amines were chosen as counter ions, and the prepared ion pairs were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The in vivo pharmacokinetic performance of ZAL was studied on rabbits following transdermal and intravenous administration. A deconvolution method was applied to determine the correlation between the in vitro permeation and the in vivo absorption. Acetic acid-induced writhing response was conducted on mice to evaluate the analgesic effect. In vitro permeation results showed that both ion pairs and chemical enhancers were effective in modulating ZAL skin permeation from patches. The enhancement ratio was negatively correlated to the polar surface area (PSA) of counter ions, and was positively correlated to the octanol-water partition coefficient (log Ko/w) of chemical enhancers, respectively. The optimized formulation contained 10% (w/w) ZAL-triethylamine and 10% (w/w) isopropyl myristate, with DURO-TAK® 87-4098 as the pressure sensitive adhesive matrix. Furthermore, the in vitro permeation data were well correlated with the in vivo absorption data. The analgesic effect of the optimized patch was comparable to the commercial indometacin plasters. In conclusion, it was feasible for transdermal delivery of ZAL by the synergistic action of ion pair and chemical enhancer, and the in vitro permeation data were indicative of the in vivo performance for the developed patches.

  9. A fast and efficient determination of amines and preservatives in cough and cold liquid and suspension formulations using a single isocratic ion-pairing high performance [correction of power] liquid chromatography method.

    Paciolla, M D; Jansen, S A; Martellucci, S A; Osei, A A


    A single, highly selective ion-pairing reverse phase-high power liquid chromatography (RP-HPLC) method has been developed for the determination of amines and preservatives in a wide range of Tylenol((R)) liquid and suspension liquid products. As with many OTC products, the challenge is to quantitatively extract the analytes from difficult matrices and specifically analyze them in the presence of various excipients and flavors. Historically, separate analytical methods were used for each class of analytes (acids, bases and neutral compounds). In this method a mobile phase consisting of a buffered ion-pairing agent with acetonitrile, methanol and tetrahydrofuran was used to separate the charged amines from neutral and acidic compounds on a Phenomenex LUNA C8(2) 75 x 4.6 mm i.d. analytical column with a 3-microm particle size. The analytes include acids (benzoic acid), bases (pseudoephedrine, chlorpheniramine, dextromethorphan, doxylamine and diphenhydramine) and a neutral compound (butylparaben). The effects of pH, the chain length of the ion-pairing reagent, ionic strength and organic modifiers on the separation are discussed. The method is linear from 15 to 150% of the target amounts. The optimized method proves to be specific, robust and accurate for the analysis of the compounds.

  10. An ion-pair principle for enantioseparations of basic analytes by nonaqueous capillary electrophoresis using the di-n-butyl L-tartrate-boric acid complex as chiral selector.

    Wang, Li-Juan; Liu, Xiu-Feng; Lu, Qie-Nan; Yang, Geng-Liang; Chen, Xing-Guo


    A chiral recognition mechanism of ion-pair principle has been proposed in this study. It rationalized the enantioseparations of some basic analytes using the complex of di-n-butyl l-tartrate and boric acid as the chiral selector in methanolic background electrolytes (BGEs) by nonaqueous capillary electrophoresis (NACE). An approach of mass spectrometer (MS) directly confirmed that triethylamine promoted the formation of negatively charged di-n-butyl l-tartrate-boric acid complex chiral counter ion with a complex ratio of 2:1. And the negatively charged counter ion was the real chiral selector in the ion-pair principle enantioseparations. It was assumed that triethylamine should play its role by adjusting the apparent acidity (pH*) of the running buffer to a higher value. Consequently, the effects of various basic electrolytes including inorganic and organic ones on the enantioseparations in NACE were investigated. The results showed that most of the basic electrolytes tested were favorable for the enantioseparations of basic analytes using di-n-butyl l-tartrate-boric acid complex as the chiral ion-pair selector. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Formation of ion pairing as an alternative to improve encapsulation and anticancer activity of all-trans retinoic acid loaded in solid lipid nanoparticles

    Carneiro G


    findings are in agreement with the data obtained in the evaluation of subdiploid DNA content and cell-cycle analysis, which showed better anticancer activity for BA-RA-loaded SLNs than TA-RA-loaded SLNs and free RA. Taken together, these findings suggest that the BA-RA-loaded SLN formulation is a promising alternative for the intravenous administration of RA in the treatment of cancer.Keywords: solid lipid nanoparticles, all-trans retinoic acid, cancer, treatment, antitumor activity, ion pairing

  12. Development and validation of a sensitive LC-MS/MS method without derivatization/ion-pairing agents for etimicin quantification in rat plasma, internal ear and kidney.

    Yao, Lan; Zhou, Fang; Cai, Mingmin; Peng, Ying; Sun, Jianguo; Chen, Qianying; Jin, Xiaoliang; Wang, Guangji; Zhang, Jingwei


    Etimicin (ETM), which belongs to the newest generation of aminoglycosides (AGs), has been proven to not only maintain but also strengthen the advantages of former AGs with relatively less toxicity. Now, it is widely applied for the treatment of bacterial infections in the clinic. Nevertheless, nephrotoxicity and ototoxicity are unavoidable issues for AGs, and while ETM is no exception, the seriousness of these issues is different. To explore the reason why ETM exhibits less toxicity and to better direct the optimization and development of new AGs, it is of great necessity and importance to monitor the pharmacokinetic behaviors of ETM in its potential toxicity target organs, the kidney and internal ear, as well as in plasma. Therefore, a novel, sensitive and efficient LC-MS/MS method without derivatization or ion-pairing agents had been developed and validated for quantification of ETM in rat plasma, kidney and internal ear for the first time. This method showed good linearity over the range of 50-2000ng/mL for rat plasma/internal ear and 100-5000ng/mL for rat kidney. The precision was less than 4.4% and the accuracy was below 4.8%. Recovery and matrix effects were 71.3%-82.8% and 97.6%-108.5%, respectively. After intravenous administration of a single dose of ETM, plasma drug concentrations fit well with a two-compartmental model, and the AUC0-∞, t1/2α, t1/2β, MRT and CL were 127.96±5.52μg*h/mL, 0.53±0.03h, 3.32±1.11h, 1.01±0.03h and 234.80±10.05mL/h/kg, respectively. Particularly, ETM showed a considerably long half-life in kidney and internal ear, up to 155.96±19.95h and 83.11±26.60h, respectively, which might contribute greatly to its toxicity. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Solvent extraction of the ion-pairs of chromium(VI) and molybdenum(VI) with trioctylmethylammonium chloride and benzyldimethylcetylammonium chloride.

    Ohashi, K; Shikina, K; Nagatsu, H; Ito, I; Yamamoto, K


    The number of capriquat molecules per chromium(VI) atom in the chromate-capriquat ion-association complex has been found to be between one and two. The distribution ratio in the extraction of chromium(VI) with capriquat is dependent on the dielectric constant of the organic solvent, with a minimum at a dielectric constant of about 8. The absorption spectra of the ion-pair extracted into cyclohexane, carbon tetrachloride, benzene and n-butanol are very similar to that of chromate in aqueous solution. The absorption spectra of the chromium(VI)-capriquat extracts in these organic solvents gradually change to an absorption spectrum similar to that of HCrO(4)(-) in aqueous solution. Chromium(VI)-capriquat extracted into chloroform and 1,2-dichloroethane gives absorption spectra similar to that of HCrO(4)(-)in aqueous medium. The chromium(VI)-capriquat species extracted into 1,2-dichloroethane may be (Q(+))(2).CrO(4)(2-)(H(2)O)(n). In contrast, chromium(VI) is extracted with capriquat into the other organic solvents from ammoniacal medium as a mixture of (Q(+))(2).CrO(4)(2-)(H(2)O)(n) and Q(+).NH(4)(+).CrO(4)(2-)(H(2)O)(n). The spectral change is ascribed to the change of the extracted species from (Q(+))(2).CrO(4)(2-)(H(2)O)(n) and Q(+)NH(4)(+).CrO(4)(-)(H(2)O)(n) to Q(+).HCrO(4)(2-)(H(2)O)(n-1). The chromium(VI)-zephiramine species extracted is formulated as (Q(+), NH(4)(+))(2)CrO(4)(2-)(H(2)O)(n).(Q(+).Cl(-))(m). Molybdenum(VI) is extracted with capriquat into the same organic solvents as a mixture of (Q(+))(2).MoO(4)(2-)(H(2)O)(n) and Q(+).NH(4)(+).MoO(4)(2-).(H(2)O)(n).

  14. Language Contact.

    Nelde, Peter Hans


    Examines the phenomenon of language contact and recent trends in linguistic contact research, which focuses on language use, language users, and language spheres. Also discusses the role of linguistic and cultural conflicts in language contact situations. (13 references) (MDM)

  15. The use of magnesium sulphate (MgSO4) for seizure prophylaxis ...


    respiratory rate and urine output are currently well recognised. .... liver function, thrombocytopenia and fetal growth restriction.[28] ... Variable. Eclampsia. N=28. Severe Pre-eclampsia. N=47 p-value (95% CI) ..... Wolf H, Boer K,Sanders GT.

  16. Analysis of sulfonylurea herbicides in water by ion-pair chromatography; Analytik von Sulfonylharnstoff-Herbiziden in Wasser mit der Ionenpaarchromatographie

    Mueller, I.A.; Wacht, U. [Hydrologische Untersuchungsstelle Salzburg (Austria)


    Sulfonylurea compounds are highly active herbicides used on golf links and on grain growing land. Reliable and sensitive methods are proposed for the determination of sulfonylureas, namely chlorsulfuron, rimsulfuron, metsulfuron-methyl, thifensulfuron-methyl, tribenuron-methyl and triasulfuron in water by ion chromatography (IC) and ion-pair chromatography (ICP) with UV-detection. For tribenuron-methyl the process by IC was validated, the detection limit for enrichment of 1 l of sample is 11 ng/l. Tribenuron-methyl however, could not be separated from metsulfuron-methyl and thifensulfuron-methyl. By application of IPC the separation of the sulfonylureas mentioned above was perfect. The detection limits were 15-20 ng/l. The pH influence during enrichment (pH=2-10) and different exposure times (pH=2 and 5) were investigated. The recovery depends on the ion character and the hydrolytic stability. Different enrichment strategies are deduced. Liquid-liquid (LPE) and solid-phase (C{sub 18}) extraction (SPE) procedures were tested. Using SPE the optimal pH for enrichment was pH=6. Recoveries ranged from 58 to 107%. The optimum for LPE was pH=5. Results of LPE- and SPE experiments with spiked pond water samples of a golf link were influenced by attendant organic substances. (orig.) [Deutsch] Die Sulfonylharnstoffe sind eine Gruppe von hochaktiven Herbiziden, die u.a. im Getreideanbau und auf Golfplaetzen angewandt werden. Zur Bestimmung der Wirkstoffe Chlorsulfuron, Rimsulfuron, Metsulfuron-methyl, Thifensulfuronmethyl, Tribenuron-methyl sowie Triasulfuron in Wasser wurden als empfindliche und fuer den Routinebetrieb geeignete Messverfahren die Ionenchromatographie (C) und die Ionenpaarchromatographie (IPC) mit UV-Detektion genutzt. Fuer den Wirkstoff Tribenuron-methyl wurde mittels IC eine Nachweisgrenze von 11 ng/l ueber das Gesamtverfahren ermittelt. Die IC ist jedoch aufgrund ungenuegender Trennleistung nur eingeschraenkt anwendbar; die Wirkstoffe Metsulfuron

  17. PENENTUAN KADAR IODIDA DAN IODAT DALAM GARAM BERIODIUM DENGAN METODE KROMATOGRAFI CAIR KENERJA TINGGI PASANGAN ION [Determination of Iodate and Iodide Content in Iodized Salt By Ion Pair High Performance Liquid Chromatography Method

    Wisnu Cahyadi1


    Full Text Available Two species of iodine, i.e. iodide and iodate in commercial iodized salt were determined using ion pair HPLC. From 15 samples analysed, the iodide and iodate content ranged from 24,05 ± 2,51 to 70,25 ± 3,78 ppm and from 31,43 ± 8,10 to 87,59 ± 0,44 ppm, respectively. The method used was found satisfactory in terms of precission, accuracy, sensitivity and selectivity, therefore the method seem acceptable for the determination of iodide and iodate content in iodized salt samples.

  18. Visual colorimetry for trace antimony(V) by ion-pair solid-phase extraction with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) on a PTFE type membrane filter.

    Mizuguchi, Hitoshi; Matsuda, Yuki; Mori, Takehito; Uehara, Atsushi; Ishikawa, Yuta; Endo, Masatoshi; Shida, Junichi


    A new visual colorimetry for trace antimony(V) based on ion-pair solid-phase extraction to a PTFE-type membrane filter with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) ion ([Co(5-Cl-PADAP)(2)](+)) has been developed. Experiments showed that hexachloroantimonate(V) ion (SbCl(6)(-)) was adsorbed with [Co(5-Cl-PADAP)(2)](+) to the front surface of the PTFE filter. The adsorption of antimony(V) ion was promoted by the addition of lithium chloride as a source of chloride ion. The excess reagent of [Co(5-Cl-PADAP)(2)](+) was eluted by rinsing with a 10 wt% methanol aqueous solution. In this case, the slow rate of the hydrolysis reaction of SbCl(6)(-) and the difference of the hydrophobicity of the ion pairs were important for adsorption and separation with a PTFE-type membrane filter. The antimony(V) concentration was determined through a visual comparison with a standard series. The visual detection limit was 0.10 microg. The calibration curve assessed with the reflection spectrometric responses at 580 nm was linear in the concentration range of 0.10 - 1.2 microg (r = 0.996). The proposed method has been applied to the determination of sub-microgram levels of antimony(V) ion in water samples.

  19. Reversed-phase ion-pair liquid chromatographic method for determination of reaction equilibria involving ionic species: exemplification of the method using ligand substitution reactions of ethylenediaminetetraacetatochromium(III) ion with acetate and phosphate ions.

    Sato, Emiko; Miya, Seiko; Saitoh, Kazunori; Saito, Shingo; Shibukawa, Masami


    A reversed-phase ion-pair liquid chromatographic method is presented for the determination of reaction equilibria involving ionic species of the same charge sign as reactant and product compounds. It has been demonstrated that ion-exchange chromatography or reversed-phase ion-pair chromatography is a useful tool for the determination of equilibrium constants of chemical reactions involving ionic species such as metal complexation reactions. Previous work with these methods has been based on the assumption that the limiting retention factors of the reactant and product species are constant independent of concentration of the chemical species (X) in the mobile phase, which reacts with the analyte compound. However, when all the reactant and product species are ions of the same charge sign as that of the species X, it is virtually impossible to apply these methods to the equilibrium constant determination because the retention factors of both the reactant and product species may depend on the concentration of X. In this study, an alternative approach was developed that estimates the limiting retention factors of ionic species from the dependence of the retention factor on the ionic strength of the mobile phase. Ligand substitution reactions of ethylenediaminetetraacetatochromium(III) ion with acetate and phosphate ions were used as model reactions to test this method. The equilibrium constants determined by this method are in good agreement with those obtained by a UV-visible spectrophotometric method.

  20. Hot-water and solid-phase extraction of fluorescent whitening agents in paper materials and infant clothes followed by unequivocal determination with ion-pair chromatography-tandem mass spectrometry.

    Chen, Hsin-Chang; Ding, Wang-Hsien


    A comprehensive method for the determination of four stilbene-type disulfonate and one distyrylbiphenyl-type fluorescent whitening agents (FWAs) in paper materials (napkin and paper tissue) and infant clothes was developed. FWAs were extracted from paper material and cloth samples using a hot-water extraction, and the aqueous extracts were then preconcentrated with the newly developed Oasis WAX (mixed-mode of weak anion exchange and reversed-phase sorbent) solid-phase extraction cartridge. The analytes were unequivocal determined by ion pair chromatography coupled with negative electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS-MS), applying a di-n-hexyl-ammonium acetate (DHAA) as the ion-pairing reagent in mobile phase. Limits of quantitation (LOQ) were established between 0.2 and 0.9 ng/g in 2 g of samples. Recovery of five FWAs in spiked commercial samples was between 42 and 95% and RSD (n = 3) ranging from 2 to 11%. The method was finally applied to commercial samples, showing that two stilbene-type disulfonates were predominant FWAs detected in napkin and infant cloth samples.

  1. Selective and sensitive speciation analysis of Cr(VI) and Cr(III) in water samples by fiber optic-linear array detection spectrophotometry after ion pair based-surfactant assisted dispersive liquid-liquid microextraction.

    Yousefi, Seyedeh Mahboobeh; Shemirani, Farzaneh


    A simple ion pair based-surfactant assisted dispersive liquid-liquid microextraction (IP-SA-DLLME) was evaluated for extraction and preconcentration of Cr(VI) and Cr(III) in aqueous samples. In this method, which was used for the first time for chromium speciation analysis, sodium dodecyl sulfate (SDS) was used as both ion-pairing and disperser agent. Cr(VI) ions were converted into their cationic complex with 1,5-diphenylcarbazide (DPC) and then extracted into 1-octanol dispersed in aqueous solution. Cr(III) ion also can be determined by this procedure after oxidation to Cr(VI). After extraction and phase separation, upper organic phase was transferred to a micro cell of a fiber optic-linear array detection spectrophotometry (FO-LADS). The effects of various parameters on the extraction recovery were investigated. Under the optimized conditions and preconcentration of 10 mL of sample, the enrichment factor of 159 and the detection limit of 0.05 μgL(-1) were obtained. Validation of the method was performed by spiking-recovery method and comparison of results with those obtained by ET-AAS method.

  2. Determination of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxyethylamphetamine, and 3,4-methylenedioxymethamphetamine in urine by online solid-phase extraction and ion-pairing liquid chromatography with detection by electrospray tandem mass spectrometry.

    Wu, Ti-Yu; Fuh, Ming-Ren


    A method using an online solid-phase extraction (SPE) and ion-pairing liquid chromatography with electrospray tandem mass spectrometry (LC/ES-MS/MS) was developed for determination of amphetamine (Amp), methamphetamine (mAmp), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxyethylamphetamine (MDEA), and 3,4-methylenedioxymethamphetamine (MDMA) in urine samples. A SPE cartridge column with both hydrophilic and lipophilic functions was utilized for online extraction. A reversed-phase C18 LC column was employed for LC separation and MS/MS was used for detection. Trifluoroacetic acid was added to the mobile phase as an ion-pairing reagent. This method was fully automated and the extraction and analysis procedures were controlled by a six-port switch valve. Recoveries ranging from 85-101% were measured. Good linear ranges (10-500 ng/mL) for Amp and mAmp were determined. For MDA, MDMA and MDEA, dual linear ranges were obtained from 5-100 and 100-500 ng/mL, respectively. The detection limit of each analytical compound, based on a signal-to-noise ratio of 3, ranged from 1-3 ng/mL. The applicability of this newly developed method was examined by analyzing several urine samples from drug users. Good agreement was obtained between the results from this method and a literature GC/MS method.

  3. Theoretical Study on the Geometrical and Electronic Structures of Choline Chloride Ion Pair%氯化胆碱离子对几何及电子结构的量子化学研究

    劳旺梅; 孙慧


    采用密度泛函理论方法,在B3 LYP/6-31G(d,p)水平上研究氯化胆碱离子对的几何与电子结构.共有四种稳定离子对构型被发现.在稳定离子对结构中,Cl-离子倾向与阳离子形成多重稳定氢键.阴阳离子间的氢键相互作用主要通过Cl-离子的LPcl轨道和阳离子的σC-H*,或σC-H*轨道间的相互作用完成.研究发现这种σ相互作用很弱,由此判断阴阳离子间大的相互作用能并不是单纯的氢键作用能,还包含阴阳离子间静电作用能的贡献;而且是主要贡献.阴阳离子间大的相互作用能还为氯化胆碱的高熔点提供了解释.%The geometrical and electronic structures of choline chloride ion pair have been studied by performing density functional theory calculations on the B3LYP/6-31G(d,p) level. Four stable configurations for choline chloride ion pair have been obtained. It is found that there exist multiply hydrogen bonds between cation and Cl-anion. The intrinsic hydrogen bond interaction between the cation and Cl- anion mainly occurs between one LPC1 of Cl- anion and the σ*C-H or σ*O-H orbitals of the cation moiety. However, the σ-type interactions are weak. Therefore, it is considered that ion pair is highly stable owing to not only the multiple hydrogen bond interactions, but also the strong electrostatic attraction. The large interaction energy between the cation and Cl- anion may be responsible for the higher melting point of choline chloride.

  4. 电导法测定298.15K时硫酸氧钒离子对解离常数%Determination of the Constant at 298.15 K Vanadyl Sulfate Ion-Pair Dissociation Using Electric Conductivity

    张书弟; 翟玉春; 严川伟


    为优化钒电池电解液配比和设置合理的充放电制度,需弄清自由钒离子活度和离子对的解离常数及其热力学性质.研究了电导法测定在298.15 K时水溶液中VOSO4.3.53H2O(s)的电导率,利用Origin数据拟合求出极限摩尔电导;采用改进的Ostwald稀释定律和改进的Davies方程求解活度系数,进而求得溶液的真实离子强度;采用Fuoss方法求解硫酸氧钒离子对的解离常数.经过数据处理得到298.15 K时硫酸氧钒极限摩尔电导率Λ0为203.2520325 S.dm2.mol-1,硫酸氧钒离子对的解离常数Kd为0.001 961 62,为电池性能有关的热力学性质提供了基础数据.%To optimize electrolyte ratio of the vanadium redox flow battery and set a reasonable charge and discharge system, the free vanadium ion activity, ion-pair dissociation constant and other thermodynamic properties should be clarified. The conductivity of the VOSO4· 3.53H20(s) in aqueous solution was determined using the electric conductivity method at 298. 15 K. The limiting molar conductance was obtained using the Origin data fitting and then the activity coefficient was solved with the improved Ostwald dilution law and the Davies equation, so as to obtain the true solution ionic strength. The vanadyl sulfate ion-pair dissociation constant was calculated through the Fuoss method. The vanadyl sulfate limiting molar conductance A0 is 203.252 032 5 S-dm2· mol 1 and the vanadyl sulfate ion-pair dissociation constant K(d is 0.001 961 62, which may provide a basic data for the battery thermodynamic properties.

  5. Determination of antihyperglycemic biguanides in serum and urine using an ion-pair solid-phase extraction technique followed by HPLC-UV on a pentafluorophenylpropyl column and on an octadecyl column.

    Tahara, Kayoko; Yonemoto, Ayumi; Yoshiyama, Yuji; Nakamura, Toshiya; Aizawa, Masaaki; Fujita, Yoshikuni; Nishikawa, Takashi


    An HPLC-UV method was established for the determination of metformin and buformin in biological fluids. Metformin was not retained on particles packed in conventional solid-phase extraction cartridges; in contrast, buformin was retained too firmly and not eluted with a solvent for recovery. However, both drugs were retained on particles that had been treated with an ion-pair reagent of heptanesulfonate or dodecylsulfate and recovered almost completely. The recovered fraction was subjected to HPLC on a pentafluorophenylpropyl column which was suitable for the determination of both biguanides in serum and in urine. Limits of quantitation were low enough for clinical use, and reproducibility was high with an RSD of 0.9-2.3%. HPLC on a conventional octadecyl column was suitable only for the determination of buformin in serum since interfering peaks appeared on the chromatograms of urine samples. The method was applied to analysis of some clinical specimens.

  6. 离子对色谱法同时测定水中多种氯代酸性除草剂%Simultaneous Determination of Chlorinated Acidic Herbicides in Waters by Ion-pair Chromatography

    李晓亚; 桂建业; 张莉; 张永涛; 李科


    建立了离子对色谱法同时测定水中DCPA二元酸、4-硝基苯酚、麦草畏、苯达松、2,4-二氯苯乙酸、2-甲基-4-氯苯氧乙酸(MCPA)、2-(4-氯苯氧基-2甲基)丙酸(MCPP)、3,5-二氯苯甲酸、2,4-滴丙酸9种氯代酸性除草剂.通过加入离子对试剂使多种极性强、保留弱的酸性除草剂在普通的反相色谱柱上同时分离.采用Shim-pack VP-ODS色谱柱,流动相为V(1-辛烷三乙磷酸铵溶液)∶V(乙腈)∶V(甲醇)=6∶3∶1,流速1.8 mL/min,不同组分全流程方法检出限范围为0.03~0.15μg/L,相对标准偏差在10%以下.建立的方法可将9种除草剂完全分离,与高效液相色谱法和气相色谱-质谱法相比,具有操作简单、分离效果好、回收率高、干扰少的优点,能够满足不同水质的检测要求.%A method for the simultaneous detection of several chlorinated acid herbicides such as dicamba and bentazon etc by ion-pair chromatography was developed. Several strongly polar and weak reserve chlorinated acid herbicides can be separated simultaneously from reversed-phase chromatography column by adding ion-pair reagent. Shim-pack VP-ODS column was used for analyte separation with ion-pair solution and the mobile phase was at a constant flow rate of 1. 8 mL/min. Extraction condition, ion-pair and the mobile phase were selected and optimized. The detection limit ranges of the method for different herbicides were 0. 03 to 0. 15 μg/L with RSD less than 10% . Comparing with high performance liquid chromatography and gas chromatography-mass spectrometry, the established method completely separates the 9 sorts of herbicides with advantages of simple operation, high separating effect, high recoveries and less interferences, which meet the requirements of all kind of water.

  7. Formation of an Ion-Pair Molecule with a Single NH+...Cl- Hydrogen Bond: Raman spectra of 1,1,3,3-Tetramethylguanidinium chloride in the solid state, in solution and in the vapor phase

    Berg, Rolf W.; Riisager, Anders; Fehrmann, Rasmus


    Some ionic compounds (salts) form liquids when heated to temperatures in the range of 200-300 °C. They may be referred to as moderate temperature ionic liquids. An example of such a compound is the 1,1,3,3- tetramethylguanidinium chloride, [TMGH]Cl, melting at ∼212 °C. The chemistry...... scattering spectra are presented and assigned, by comparing to the quantum mechanical calculations. It is concluded that dimeric molecular ion pairs with four N-H+ · · · Cl- hydrogen bonds probably exist in the solutions and are responsible for the relatively high solubility of the “salt” in ethanol......- hydrogen bond, the stretching band of which is causing the band....

  8. Simultaneous detection of green tea catechins and gallic acid in human serum after ingestion of green tea tablets using ion-pair high-performance liquid chromatography with electrochemical detection.

    Narumi, Keiko; Sonoda, Jun-Ichiro; Shiotani, Keita; Shigeru, Michihiro; Shibata, Masayuki; Kawachi, Akio; Tomishige, Erisa; Sato, Keizo; Motoya, Toshiro


    We developed an analytical method for the simultaneous determination of tea catechins and gallic acid (GA) in human serum using ion-pair high-performance liquid chromatography (HPLC) with electrochemical detection. GA was measured to estimate the amount of gallate moiety produced by degradation of gallated catechins ((-)-epicatechin-3-gallate, ECG; (-)-epigallocatechin-3-gallate, EGCG). Ethyl gallate was adopted as an internal standard to correct for the extraction efficiency. To maximize extraction efficiency, a hydrophobic polytetrafluoroethylene (PTFE) filter was selected for pre-treatment prior to separation. HPLC separation was performed using a C18 reversed-phase column with a gradient mobile phase of phosphate buffer (pH 2.5) containing tetrahexylammonium hydrogensulfate as an ion-pair reagent. Using this method, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), ECG, EGCG, ethyl gallate, and GA were detected as single peaks. The resolution values for target analytes were 4.0-13.0 and the mean values of the absolute recoveries of catechins and GA were 77.3-93.9%. The detection limits for catechins and GA in serum were 0.4-3.1ng/mL. The serum catechin levels of eight healthy volunteers after ingestion of a single dose of green tea tablets were measured using this method. The concentration of total catechins (free+conjugated forms) in serum peaked 60min after ingestion. From these results, this method is thought to enable the simultaneous quantification of GA, the hydrolysis product of gallated catechins, and target catechins, and to be sufficiently sensitive for pharmacokinetic studies of catechins following oral administration of green tea.

  9. 离子对色谱-间接紫外检测法分析哌啶离子液体阳离子%Determination of piperidinium ionic liquid cations by ion-pair chromatography-indirect ultraviolet detection

    王淼煜; 于泓; 李萍; 李杰; 高玉凤


    A method was developed for the determination of piperidinium cations by ion-pair chromatography with indirect ultraviolet detection. Chromatographic separation was performed on a reversed-phase C18 column using background ultraviolet absorption reagent-ion-pair rea-gent/organic solvent as mobile phase. The effects of the background ultraviolet absorption rea-gent,detection wavelength,ion-pair reagent,organic solvent,column temperature and flow rate on the determination of piperidinium cations were investigated and the retention rules were studied. The optimized chromatographic conditions for the determination of piperidinium cat-ions were as follows:mobile phase,0. 5 mmol/L 4-aminophenol hydrochloride-0. 1 mmol/L 1-heptanesulfonic acid sodium aqueous solution/methanol(80:20,v/v);detection wavelength, 210 nm;column temperature,30 ℃;flow rate,1. 0 mL/min. Under these conditions,the three piperidinium cations were baseline separated within 4 min. The detection limits( S/N=3)of the piperidinium cations were 0. 137-0. 545 mg/L. The relative standard deviations( n=5)for peak area and retention time were 0. 72% and 0. 37% respectively. The method has been successfully applied to the determination of piperidinium cations in ionic liquids synthesized by chemistry laboratory. The recoveries of piperidinium cations after spiking were 97. 0%-98. 4%. The method is simple,rapid,reproducible,linear,and can meet the quantitative analysis requirement for the determination of piperidinium cations.%建立了快速分析无紫外光吸收的哌啶离子液体阳离子的离子对色谱-间接紫外检测法。采用反相 C18色谱柱,以背景紫外吸收试剂-离子对试剂水溶液/有机溶剂为流动相分离哌啶离子液体阳离子。研究了背景紫外吸收试剂、检测波长、离子对试剂、有机溶剂、柱温、流速对分离测定哌啶阳离子的影响。最佳色谱条件为:以0.5 mmol/L对氨基苯酚盐酸盐-0.1 mmol/L庚

  10. Reversed-phase ion-pair chromatography-diode array detection of the bispyridinium compound MB327: plasma analysis of a potential novel antidote for the treatment of organophosphorus poisoning.

    John, Harald; Mikler, John; Worek, Franz; Thiermann, Horst


    In the case of poisoning by organophosphorus nerve agents or pesticides, there is still a lack of pharmacological treatment of the cholinergic crisis selectively targeting the nicotinic acetylcholine receptor. Recently, the compound MB327 was identified as a potential novel lead structure to close this gap, thus demanding a quantitative assay for initial pharmacokinetic (PK) studies. MB327 is a salt consisting of the dicationic bispyridinium compound (BPC) 1,1´-(propane-1,3-diyl)bis(4-tert-butylpyridinium) and two iodide counter ions. Due to the permanent positive charge of the BPC, an isocratic reversed-phase ion-pair chromatographic separation (RPIPC) was developed using heptanesulfonic acid as ion-pairing reagent and 45% v/v methanol as organic modifier (1 mL/min). Selective UV-detection (230 nm) was done by a diode array detector (DAD) for reliable, rugged, precise (RSD < 7%) and accurate (96-104%) quantitative analysis of 50 μL swine plasma (linear range 1-1000 µg BPC/mL plasma, lower limit of quantification 2 µg/mL). During method validation, diverse parameters essential for the chromatographic process were investigated to generate van´t Hoff, van Deemter and width plots allowing calculation of thermodynamic data like the distribution constant K (5.7 ± 0.3), change in enthalpy, ΔH(0) : -23.66 kJ/mol, and entropy, ΔS(0) : -65 J/(mol*K). In addition, RPIPC-DAD analysis enabled calculation of molar absorptivities of the BPC, ε230 : 17 400 ± 1100 L/(mol*cm), and iodide, ε230 : 9900 ± 400 L/(mol*cm), which determination was hampered by interference with each other in conventional cuvette UV-spectrophotometric measurements. Finally, the RPIPC-DAD procedure was applied to samples from an in vivo study of swine.

  11. Development of a Single Ion Pair HPLC Method for Analysis of Terbinafine, Ofloxacin, Ornidazole, Clobetasol, and Two Preservatives in a Cream Formulation: Application to In Vitro Drug Release in Topical Simulated Media-Phosphate Buffer Through Rat Skin.

    Dewani, Anil P; Bakal, Ravindra L; Kokate, Pranjali G; Chandewar, Anil V; Patra, Srdhanjali


    Present work reports an HPLC method with UV detection for quantification of terbinafine, ofloxacin, ornidazole, and clobetasol in a cream formulation along with two preservatives methyl and propyl paraben. The chromatographic separation and quantification was achieved by an octyl bonded column and a gradient elution program involving an ion-pairing reagent, hexanesulfonic acid (0.2%, pH modified to 2.7 using orthophosphoric acid) and acetonitrile. The method was simple and devoid of buffer salts and therefore advantageous for system and column life. The three step gradient program was initiated with 30% (v/v) acetonitrile for the first 5 min and ramped linearly to 60% in the next 7 min. The mobile phase remained constant for the next 11 min and then concluded at 30% (v/v) of acetonitrile. Flow rate throughout was 0.8 mL/min, and all the signals were monitored at 243 nm. The method was applied for assay of a cream formulation and its in vitro permeation studies to determine the penetration profile of the four drugs and two preservatives. A marketed cream formulation was selected for the permeation study, which was carried out using a diffusion cell consisting of topical simulated media, phosphate buffer (pH=6.8) solution containing 1% sodium lauryl sulfate as a receiver medium.

  12. 反相离子对高效液相色谱法测定啤酒中的B族维生素%Determination of B Vitamins in Beer by Ion-pair Reversed Phase High Performance Liquid Chromatography

    陈新; 张风; 李健


    A method had been developed by Ion-pair RP-HPLC for simultaneous determination of eight water-soluble B vitamins (thiamine, ri-boflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid and cobalamin) in beer. The method had excellent linearity with the correlation coefficients over 0.9993. And its average spike recovery varied from 98.04%to 103.27%with RSD within the range of 0.32%~1.26%.%建立反相离子高效液相色谱同时分离检测硫胺素VB1,核黄素VB2,烟酸VB3,泛酸VB5,吡哆素VB6,生物素VB7,叶酸VB9,钴胺素VB12的分析方法。结果表明,B族维生素各组分线性良好,各线性相关系数都在0.9993以上;并用此方法测定啤酒中B族维生素。平均回收率为98.04%~103.27%,其RSD为0.32%~1.26%。

  13. In situ synthesis of twelve dialkyltartrate-boric acid complexes and two polyols-boric acid complexes and their applications as chiral ion-pair selectors in nonaqueous capillary electrophoresis.

    Wang, Li-Juan; Yang, Juan; Yang, Geng-Liang; Chen, Xing-Guo


    In this paper, twelve dialkyltartrate-boric acid complexes and two polyols-boric acid complexes were in situ synthesized by the reaction of different dialkyltartrates or polyols with boric acid in methanol containing triethylamine. All of the twelve dialkyltartrate-boric acid complexes were found to have relatively good chiral separation performance in nonaqueous capillary electrophoresis (NACE). Their chiral recognition effects in terms of both enantioselectivity (α) and resolution (R(s)) were similar when the number of carbon atoms was below six in the alkyl group of alcohol moiety. The dialkyltartrates containing alkyl groups of different structures but the same number of carbon atoms, i.e. one of straight chain and one of branched chain, also provided similar chiral recognition effects. Furthermore, it was demonstrated for the first time that two methanol insoluble polyols, D-mannitol and D-sorbitol, could react with boric acid to prepare chiral ion-pair selectors using methanol as the solvent medium. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Characterization of selenium species in biological extracts by enhanced ion-pair liquid chromatography with inductively coupled plasma-mass spectrometry and by referenced electrospray ionization-mass spectrometry

    Kotrebai, Mihály; Bird, Susan M.; Tyson, Julian F.; Block, Eric; Uden, Peter C.


    Selenium is an essential nutrient for humans; selenium compounds catalyze intermediate metabolism reactions and inhibit the toxic effects of heavy metals such as arsenic, cadmium and mercury. Some extracts of selenium-enriched biological materials show cancer preventive effects, tentatively attributable to the biological functions of selenoamino acids. An improved ion pair chromatographic method with methodological enhancements for the separation, qualitative and quantitative determination of non-volatile selenium compounds extracted from different samples has been developed using ICP-MS as an element-selective detector. Separation power early in the chromatogram was increased to baseline separation in the standard mixture as a result of decreasing spray chamber size from 97 to 14 ml, and increasing trifluoracetic acid (TFA) concentration in the mobile phase from 0.1 to 0.6%. The former pH was restored by the addition of ammonia to the mobile phase, which also served to increase the column recovery of inorganic anions. Calibration curves for different selenoamino acids showed statistically different behavior. Biological sample extracts were characterized using HPLC-ICP-MS. Mass spectral behavior of selenoamino acids, using electrospray and ion trap technology with direct infusion and liquid chromatographic sample introduction, is also reported.


    刘德萍; 杨军


    Venouis blood(10ml) from doped ox was treated with heparin sodiumand centrifuged for 10min.A 0.5ml portion of the plasma obtained was vortexed with 1μg pipemidic acid(internal standard),0.1ml phosphate buffer of pH7.4 and 2ml CH2Cl2 for 1min and centrifuged for 10min.The organic extract was evaporated and the residue was dissolved in 0.1ml mobile phase.Enrofloxacin(ERFX) in the solution were separated and determined by HPLC on a Shim-pack CLC-ODS column (15cm×6mm i.d.),operated at 36℃,with 25m M-tetrabutylammonium hydroxide/methanol at pH 3(4∶1) as mobile phase at 1ml/min and detection at 272nm.The calibration graph for ERFX was linear from 0.2~3mg/l.Recoveries were 99.4% with RSD of 2.06%.The method was also used in the pharmacokinetic study of ERFX.Key words:reversed-phase ion-pair high-performance liquid chromatography; enrofloxacin; animal plasma

  16. Prioritized Contact Transport Stream

    Hunt, Walter Lee, Jr. (Inventor)


    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  17. Non-Catalytic and MgSO4 - Catalyst based Degradation of Glycerol in Subcritical and Supercritical Water Media

    Mahfud Mahfud


    Full Text Available This research aims to study the glycerol degradation reaction in subcritical and supercritical water media. The degradation of glycerol into other products was performed both with sulphate salt catalysts and without catalyst. The reactant was made from glycerol and water with the mass ratio of 1:10. The experiments were carried out using a batch reactor at a constant pressure of 250 kgf/cm2, with the temperature range of 200-400oC, reaction time of 30 minutes, and catalyst mol ratio in glycerol of 1:10 and 1:8. The products of the non-catalytic glycerol degradation were acetaldehyde, methanol, and ethanol. The use of sulphate salt as catalyst has high selectivity to acetaldehyde and still allows the formation alcohol product in small quantities. The mechanism of ionic reaction and free radical reaction can occur at lower temperature in hydrothermal area or subcritical water. Conversion of glycerol on catalytic reaction showed a higher yield when compared with the reaction performed without catalyst

  18. Mesos components (CaC12, MgSO4, KH2P04) are critical for improving pear micropropagation

    The USDA-ARS National Clonal Germplasm Repository in vitro collection contains over 200 pear accessions in 18 species. Due to the wide genetic diversity of this collection there is also a diverse response to growth on standard tissue culture media. An initial study of mineral nutrition using a syste...

  19. Characterization of halophiles in natural MgSO 4 salts and laboratory enrichment samples: Astrobiological implications for Mars

    Foster, Ian S.; King, Penelope L.; Hyde, Brendt C.; Southam, Gordon


    The presence of sulfate salts and limited subsurface water (ice) on Mars suggests that any liquid water on Mars today will occur as (magnesium) sulfate-rich brines in regions containing sources of magnesium and sulfur. The Basque Lakes of British Columbia, Canada, represent a hypersaline terrestrial analogue site, which possesses chemical and physical properties similar to those observed on Mars. The Basque Lakes also contain diverse halophilic organisms representing all three Kingdoms of life, growing in surface and near-subsurface environments. Of interest from an astrobiological perspective, crushed magnesium sulfate samples that were analyzed using a modified Lowry protein assay contained biomass in every crystal inspected, with biomass values from 0.078 to 4.21 mg biomass/g salt; average=0.74±0.7 mg biomass/g salt. Bacteria and Archaea cells were easily observed even in low-biomass samples using light microscopy, and bacteria trapped within magnesium sulfate crystals were observed using confocal microscopy. Regions within the salt also contained bacterial pigments, e.g., carotenoids, which were separate from the cells, indicating that cell lysis might have occurred during entrapment within the salt matrix. These biosignatures, cells, and any 'soluble' organic constituents were primarily found trapped within fluid inclusions or fluid-filled void spaces between intergrown crystals. Diffuse reflectance infrared Fourier transform spectroscopy (reflectance IR) analysis of enrichment cultures, containing cyanobacteria, Archaea, or dissimilatory sulfate-reducing bacteria, highlighted molecular biosignature features between 550-1650 and 2400-3000 cm -1. Spectra from natural salts demonstrated that we can detect biomass within salt crystals using the most sensitive biosignatures, which are the 1530-1570 cm -1, C-N, N-H, -COOH absorptions and the 1030-1050 cm -1 C-OH, C-N, PO 43- bond features. The lowest detection limit for a biosignature absorption feature using reflectance IR was with a natural sample that possessed 0.78 mg biomass/g salt. In a model cell, i.e., a 0.5 by 1 μm bacillus, this biomass value corresponds to approximately 7.8×10 8 cells/g salt. Based on its ability to detect biomass entrapped within natural sulfate salts, reflectance IR may make an effective remote-sensing tool for finding enrichments of organic carbon within outcrops and surficial sedimentary deposits on Mars.

  20. Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.

    Wang, Liming; Wei, Jingjing; Su, Zhaohui


    High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis.

  1. Liberation of H2 from (o-C6H4Me)3P—H(+) + (-)H—B(p-C6F4H)3 ion-pair: A transition-state in the minimum energy path versus the transient species in Born-Oppenheimer molecular dynamics

    Pu, Maoping; Heshmat, Mojgan; Privalov, Timofei


    Using Born-Oppenheimer molecular dynamics (BOMD) with density functional theory, transition-state (TS) calculations, and the quantitative energy decomposition analysis (EDA), we examined the mechanism of H2-liberation from LB—H(+) + (-)H—LA ion-pair, 1, in which the Lewis base (LB) is (o-C6H4Me)3P and the Lewis acid (LA) is B(p-C6F4H)3. BOMD simulations indicate that the path of H2 liberation from the ion-pair 1 goes via the short-lived transient species, LB⋯H2⋯LA, which are structurally reminiscent of the TS-structure in the minimum-energy-path describing the reversible reaction between H2 and (o-C6H4Me)3P/B(p-C6F4H)3 frustrated Lewis pair (FLP). With electronic structure calculations performed on graphics processing units, our BOMD data-set covers more than 1 ns of evolution of the ion-pair 1 at temperature T ≈ 400 K. BOMD simulations produced H2-recombination events with various durations of H2 remaining fully recombined as a molecule within a LB/LA attractive "pocket"—from very short vibrational-time scale to time scales in the range of a few hundred femtoseconds. With the help of perturbational approach to trajectory-propagation over a saddle-area, we directly examined dynamics of H2-liberation. Using EDA, we elucidated interactions between the cationic and anionic fragments in the ion-pair 1 and between the molecular fragments in the TS-structure. We have also considered a model that qualitatively takes into account the potential energy characteristics of H—H recombination and H2-release plus inertia of molecular motion of the (o-C6H4Me)3P/B(p-C6F4H)3 FLP.

  2. Luminescent ion pairs with tunable emission colors for light-emitting devices and electrochromic switches† †Electronic supplementary information (ESI) available: Details of NMR and MS spectra. See DOI: 10.1039/c6sc02837c Click here for additional data file.

    Guo, Song; Huang, Tianci; Liu, Shujuan; Zhang, Kenneth Yin; Yang, Huiran; Han, Jianmei


    Most recently, stimuli-responsive luminescent materials have attracted increasing interest because they can exhibit tunable emissive properties which are sensitive to external physical stimuli, such as light, temperature, force, and electric field. Among these stimuli, electric field is an important external stimulus. However, examples of electrochromic luminescent materials that exhibit emission color change induced by an electric field are limited. Herein, we have proposed a new strategy to develop electrochromic luminescent materials based on luminescent ion pairs. Six tunable emissive ion pairs (IP1–IP6) based on iridium(iii) complexes have been designed and synthesized. The emission spectra of ion pairs (IPs) show concentration dependence and the energy transfer process is very efficient between positive and negative ions. Interestingly, IP6 displayed white emission at a certain concentration in solution or solid state. Thus, in this contribution, UV-chip (365 nm) excited light-emitting diodes showing orange, light yellow and white emission colors were successfully fabricated. Furthermore, IPs displayed tunable and reversible electrochromic luminescence. For example, upon applying a voltage of 3 V onto the electrodes, the emission color of the solution of IP1 near the anode or cathode changed from yellow to red or green, respectively. Color tunable electrochromic luminescence has also been realized by using other IPs. Finally, a solid-film electrochromic switch device with a sandwiched structure using IP1 has been fabricated successfully, which exhibited fast and reversible emission color change. PMID:28451179

  3. Lipstick Induced Contact Leucoderma

    Gupta Lalit Kumar; Jain Suresh Kumar; Khare Ashok Kumar


    Lipstick is a commonly used cosmetic. Its use may sometimes lead to contact dermatitis. Contact leucoderma to lipsticks however, is not common. We report a patient developing contact leucoderma to lipstick in association with contact dermatitis.

  4. Lipstick Induced Contact Leucoderma

    Gupta Lalit Kumar


    Full Text Available Lipstick is a commonly used cosmetic. Its use may sometimes lead to contact dermatitis. Contact leucoderma to lipsticks however, is not common. We report a patient developing contact leucoderma to lipstick in association with contact dermatitis.

  5. Preparation and characterization of baicalin-sanguinarine ion-pair chitosan nanoparticles%黄芩苷-血根碱离子对壳聚糖纳米粒的制备及表征

    赵静; 曾建国; 邹剑锋; 刘德明; 肖俐; 徐丽


    目的 以离子凝胶法制备黄芩苷-血根碱离子对壳聚糖纳米粒(BSI-CS-NPs).方法 以单因素为主要考察方法,筛选最佳处方和制备工艺;采用透射电子显微镜(TEM)观察BSI-CS-NPs的形态,激光粒度分析仪测定粒径大小和Zeta电位,HPLC法检测包封率和载药量.结果 所制BSI-CS-NPs外观圆整,粒度分布均匀,平均粒径为326.4 nm,Zeta电位为45.7 mV,包封率为68.73%,载药量为26.68%.相比黄芩苷-血根碱离子对原料药,BSI-CS-NPs 2 h的药物累积释放率减少了约36.51%,12h累积释放率为92.29%.结论 离子凝胶法适用于BSI-CS-NPs的制备,且具有缓释性能.%Objective To prepare chitosan nanoparticles loading baicalin-sanguinarine ion-pair (BSI-CS-NPs) by ionic gelation method. Methods Based on the results of single factor experiments, four factors affecting the formulation were optimized by orthogonal design. The diameters and the Zeta potentials were measured by laser particle size analyzer. Transmission electron microscope (TEM) was used to observe the particle shapes, and HPLC was used to determine the entrapment efficiency and loading rate. Results The mean particle size was found to be 326.4 nm with a narrow particles distribution of polydispersity index. The Zeta potential of the optimized method-loaded chitosan nanoparticles was 45.7 Mv, the drug entrapment efficiency was 26.68%, and the loading rate was 68.73%. The drug release degree of BSI-CS-NPs decreased about 36.51% in 2 h compared with BSI solution and the total drug release degree in 12 h was 92.29% with the sustained releasing behavior. Conclusion The method of ionic gelation is appropriate for the preparation of BSI-CS-NPs, and the BSI-CS-NPs have sustained releasing effect.

  6. Determination of plasma pseudoephedrine with ion pair chromatography%反相离子对色谱法测定人血浆盐酸伪麻黄碱浓度

    罗会盛; 张宏文; 刘强辉; 朱蓉蓉


    Objective To develop a high-performance liquid chromatography ( HPLC) method for determination of pseudoephedrine hydrochloride( PSE) in human plasma. Methods The analytical column was packed with SupEIXX) discovery-C18 (250 mm× 4. 6 mm, 5 μm) column. The mobile phase was consisted of acetonitrile and a buffer solution(6 mmol/L heptanesulfonate sodium salt. 60 mmol/L sodiumdihydrogen phosphate.0. 3% triethylamine ) (19 : 81) and the flow rate was 1.0 ml/min. The UV detection wavelength was 190 ran Results A good linearity in the range of 10-1000 μg/L was achieved. The determination limit was 10 μg/L. The RSD of intra-day was less than 10% and the RSD of inter-day was less than 12%. The recovery was more than 84. 85%. Conclusion The ion pair chromatography is simple, sensitive and accurate, and can be used for the studies of pharmacokinetics of PSE in human.%目的 建立反相高效液相色谱法检测人血浆中盐酸伪麻黄碱浓度的方法.方法 采用SupELCOdiscoveryC18(250 mn×4.6m,5μm)色谱柱,乙腈-水为流动相,流速1.0 ml/min,检测波长190 nm,柱温25C.结果 盐酸伪麻黄碱浓度在10-1000 μg/L范围内线性良好(γ=0.9991),最低检测限为10μg/L.批内相对标准偏差(RSD)<10%,批间RSD<12%;提取回收率为84.85%.结论 反相高效液相色谱法简便、快速、准确,可用于人体内伪麻黄碱的血药浓度测定及药动学研究.

  7. 离子对高效液相色谱法测定舒必利片的含量及有关物质%Determination of Sulpiride Tablets′ content and related substances by ion-pair HPLC



    目的 建立反相离子对高效液相色谱法测定舒必利片的含量及有关物质.方法 采用反相离子对高效液相色谱法.色谱柱:Agilengt ZORBAX SB-C18(150 mm×4.6 mm,5 μm);流动相:磷酸二氢钾缓冲液(取磷酸二氢钾6.8 g,辛烷磺酸钠1 g,加水1 000 mL使溶解,用磷酸调节pH至3.3)-乙腈-甲醇(80∶10∶10);流速:1.4 mL· min-1;柱温:35 ℃;含量检测波长均为291 nm;有关物质检测波长为240 nm.结果 在2.4~611.6 μg·mL-1范围内线性关系良好,平均回收率为100.01%,RSD为1.03%.结论 该方法专属性强,灵敏度高,操作简便、准确,可作为舒必利片的质量控制与评价方法.%Objective To establish an ion-pair reversed-phase HPLC method for the determination of Sulpiride Tablets content and related substances. Methods The analysis was performed on an Agilent ZORBAX SB- C18 column(150 mm×4. 6 mm,5 μm) with the potassium dihydrogen phosphate buffer (dissolving monopotassium phosphate 6. 8 g and sodium 1-octane sulfonate 1 g with water to 1 000 mL,and adjusted to pH 3. 3 with phosphoric acid)-acetonitrile-methanol(80 : 10 : 10) as the mobile phase at flow rate of 1. 4 mL o min-1 , detected at 291 nm for Sulpiride Tablets content and 240 nm for Sulpiride Tablets related substances. The column temperature was at 35℃. Results The calibration curves showed good linear response ranged from 2. 4 to 611. 6 μtg o mL-1 for Sulpiride Tablets' content and it' s related substances. Conclusion This method with strong specificity and high sensitivity is simple and accurate,and can be used for the quality control and evaluation of Sulpiride Tablets.

  8. EDITORIAL: Close contact Close contact

    Demming, Anna


    The development of scanning probe techniques, such as scanning tunnelling microscopy [1], has often been touted as the catalyst for the surge in activity and progress in nanoscale science and technology. Images of nanoscale structural detail have served as an invaluable investigative resource and continue to fascinate with the fantastical reality of an intricate nether world existing all around us, but hidden from view of the naked eye by a disparity in scale. As is so often the case, the invention of the scanning tunnelling microscope heralded far more than just a useful new apparatus, it demonstrated the scope for exploiting the subtleties of electronic contact. The shrinking of electronic devices has been a driving force for research into molecular electronics, in which an understanding of the nature of electronic contact at junctions is crucial. In response, the number of experimental techniques in molecular electronics has increased rapidly in recent years. Scanning tunnelling microscopes have been used to study electron transfer through molecular films on a conducting substrate, and the need to monitor the contact force of scanning tunnelling electrodes led to the use of atomic force microscopy probes coated in a conducting layer as studied by Cui and colleagues in Arizona [2]. In this issue a collaboration of researchers at Delft University and Leiden University in the Netherlands report a new device architecture for the independent mechanical and electrostatic tuning of nanoscale charge transport, which will enable thorough studies of molecular transport in the future [3]. Scanning probes can also be used to pattern surfaces, such as through spatially-localized Suzuki and Heck reactions in chemical scanning probe lithography. Mechanistic aspects of spatially confined Suzuki and Heck chemistry are also reported in this issue by researchers in Oxford [4]. All these developments in molecular electronics fabrication and characterization provide alternative

  9. Colored Contact Lens Dangers

    Full Text Available ... Vision and Daily Eye Drops After One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume Contacts May Contain Chemicals ...

  10. Colored Contact Lens Dangers

    Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...

  11. Contact Dermatitis in Pediatrics.

    Pelletier, Janice L; Perez, Caroline; Jacob, Sharon E


    Contact dermatitis is an umbrella term that describes the skin's reaction to contacted noxious or allergenic substances. The two main categories of contact dermatitis are irritant type and allergic type. This review discusses the signs, symptoms, causes, and complications of contact dermatitis. It addresses the testing, treatment, and prevention of contact dermatitis. Proper management of contact dermatitis includes avoidance measures for susceptible children. Implementation of a nickel directive (regulating the use of nickel in jewelry and other products that come into contact with the skin) could further reduce exposure to the most common allergens in the pediatric population. [Pediatr Ann. 2016;45(8):e287-e292.].

  12. Contact Angle Goniometer

    Federal Laboratory Consortium — Description:The FTA32 goniometer provides video-based contact angle and surface tension measurement. Contact angles are measured by fitting a mathematical expression...

  13. Corporate Consumer Contact API

    General Services Administration — The data in the Corporate Consumer Contact API is based on the content you can find in the Corporate Consumer Contact listing in the Consumer Action Handbook (PDF)....

  14. Colored Contact Lens Dangers

    Full Text Available ... lenses without a prescription in the United States. All contact lenses are medical devices that require a ... no such thing as a "one size fits all" contact lens. Lenses that are not properly fitted ...

  15. Dermatitis, contact (image)

    This picture shows a skin inflammation (dermatitis) caused by contact with a material that causes an allergic reaction in this person. Contact dermatitis is a relatively common condition, and can be caused ...

  16. Colored Contact Lens Dangers

    Full Text Available ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ... wear any kind of contact lens. In Butler's case, the lenses caused an infection and left her ...

  17. Colored Contact Lens Dangers

    Full Text Available ... Contact Lenses Without a Prescription Sep. 26, 2013 It started as an impulsive buy from a souvenir ... Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored contact lenses without ...

  18. Colored Contact Lens Dangers

    Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ...

  19. Colored Contact Lens Dangers

    Full Text Available ... like a suction cup." Halloween is a popular time for people to use colored contact lenses to ... wear costume contact lenses for Halloween or any time of year, follow these guidelines: Get an eye ...

  20. Colored Contact Lens Dangers

    Full Text Available ... glow-in-the-dark lizard lenses, costume contacts can certainly add a spooky, eye-popping touch. But ... consideration as a standard contact lens because they can be purchased over-the-counter or on the ...

  1. Contact Us about Asbestos

    How to contact EPA for more information on asbestos, including state and regional contacts, EPA’s Asbestos Abatement/Management Ombudsman and the Toxic Substances Control Act (TSCA) Assistance Information Service (TSCA Hotline).

  2. Colored Contact Lens Dangers

    Full Text Available ... popping touch. But colored contact lenses are popular year-round, not just at Halloween. But few know ... contact lenses for Halloween or any time of year, follow these guidelines: Get an eye exam from ...

  3. Contact lens in keratoconus

    Varsha M Rathi; Preeji S Mandathara; Srikanth Dumpati


    Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the En...

  4. Coral contact dermatitis

    Jefferson, Julie; Thompson, Curtis; Hinshaw, Molly; Rich, Phoebe


    Corals can elicit both toxic and allergic reactions upon contact with the skin. Clinical presentations vary depending on whether the reaction is acute, delayed, or chronic. Literature concerning cutaneous reactions to corals and other Cnidarians is scarce. Herein we report a case of delayed contact hypersensitivity reaction to coral and review the clinical and histopathological features of coral contact dermatitis.

  5. Coral contact dermatitis.

    Jefferson, Julie; Thompson, Curtis; Hinshaw, Molly; Rich, Phoebe


    Corals can elicit both toxic and allergic reactions upon contact with the skin. Clinical presentations vary depending on whether the reaction is acute, delayed, or chronic. Literature concerning cutaneous reactions to corals and other Cnidarians is scarce. Herein we report a case of delayed contact hypersensitivity reaction to coral and review the clinical and histopathological features of coral contact dermatitis.

  6. Contact urticaria : Present scenario

    Bhatia Ruchi


    Full Text Available Immunological contact urticaria is a hypersensitivity reaction that appears on the skin following contact with an eliciting substance. Recent advances in our understanding of the molecular mechanism and pathogenesis of this reaction have altered its classification, diagnosis, and treatment. We discuss classification, epidemiology, diagnosis, testing, and treatment options that are available to patients with contact urticaria.

  7. Types of Contact Lenses

    ... back to top ] Rigid Gas Permeable (RGP) Contact Lenses Rigid gas permeable contact lenses (RGPs) are more durable ... Ortho-K) Orthokeratology, or Ortho-K, is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the ...

  8. Mixed lubricated line contacts

    Faraon, Irinel Cosmin


    The present work deals with friction in mixed lubricated line contacts. Components in systems are becoming smaller and due to, for instance power transmitted, partial contact may occur. In industrial applications, friction between the moving contacting surfaces cannot be avoided, therefore it is essential that an engineer is able to predict friction.

  9. New Cosmetic Contact Allergens

    An Goossens


    Full Text Available Allergic and photo-allergic contact dermatitis, and immunologic contact urticaria are potential immune-mediated adverse effects from cosmetics. Fragrance components and preservatives are certainly the most frequently observed allergens; however, all ingredients must be considered when investigating for contact allergy.

  10. Analysis of Oligo-κ-carrageenan by Reversed Phase Ion-pair Ultra-Performance Liquid Chromatography Coupled with Electrospray Ionization-Time of Flight-Mass Spectrometry%κ-卡拉胶寡糖的反相离子对-超高效液相色谱-四极杆-飞行时间质谱研究

    高洋; 陈海敏; 徐继林; 陈德莹; 严小军


    A method was developed to elucidate the structures of sulfated oligosaccharides through establishment of an effective reversed phase ion pair ultra-performance liquid chromatography coupled with electrospray ionization time of flight mass spectrometry( RPIP-UPLC-ESI-TOF-MS). Heptylamine (20 mmol/L,pH4) has been selected as the ion-pairing agent.κ-Carrageenan oligosaccharides have been separated on BEH C_(18) column using MeOH/H_2O with 25% heptylammonium formate as eluent in linear gradient mode. Mass spectra were obtained by ESI-Q-TOF-MS in both positive and negative modes. κ-Carrageenan oligosaccharides were well separated up to pentatetrasaccharide,and ESIMS analysis for κ-carrageenan oligosaccharides up to hepta-cosasccharide. The results showed that all acid hydrolyzed κ-carrageenan oligosaccharides were odd sugars,which was further confirmed by polyacrylamide gel electrophoresis ( PAGE). The characteristic fragmentation pattern of ion-pair oligosaccharides in mass spectra can be applied for rapid structure identification.%建立反相离子对-超高效液相色谱(RPIP-UPLC)和电喷雾离子源-四极杆-飞行时间质谱(ESI-Q-TOF-MS)联用技术快速分离鉴定硫酸寡糖的方法.以20 mmol/L庚胺(pH 4)为离子对试剂,25%庚胺甲酸盐纯水溶液(A)和25%庚胺甲酸盐甲醇溶液(B)为梯度洗脱溶剂,κ-卡拉胶寡糖通过BEH C_(18)反相柱分离后,分别在正、负离子模式下进行四极杆-飞行时间质谱分析.结果表明,聚合度为3~45的κ-卡拉胶寡糖在BEH C_(18)柱上得到很好的分离,从每一个色谱峰对应的质谱图中可以准确获得直至27糖的各寡糖结构信息,均为奇数糖,与聚丙烯凝胶电泳结果吻合.所得的寡糖断裂规律对卡拉胶寡糖的快速鉴定和结构解析具有重要意义.

  11. Contact lens in keratoconus

    Varsha M Rathi


    Full Text Available Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP lenses, soft and soft toric lenses, piggy back contact lenses (PBCL, hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL.

  12. Modeling Thermal Contact Resistance

    Kittel, Peter; Sperans, Joel (Technical Monitor)


    One difficulty in using cryocoolers is making good thermal contact between the cooler and the instrument being cooled. The connection is often made through a bolted joint. The temperature drop associated with this joint has been the subject of many experimental and theoretical studies. The low temperature behavior of dry joints have shown some anomalous dependence on the surface condition of the mating parts. There is also some doubts on how well one can extrapolate from the test samples to predicting the performance of a real system. Both finite element and analytic models of a simple contact system have been developed. The model assumes (a) the contact is dry (contact limited to a small portion of the total available area and the spaces in-between the actual contact patches are perfect insulators), (b) contacts are clean (conductivity of the actual contact is the same as the bulk), (c) small temperature gradients (the bulk conductance may be assumed to be temperature independent), (d) the absolute temperature is low (thermal radiation effects are ignored), and (e) the dimensions of the nominal contact area are small compared to the thickness of the bulk material (the contact effects are localized near the contact). The models show that in the limit of actual contact area much less than the nominal area (a much less than A), that the excess temperature drop due to a single point of contact scales as a(exp -1/2). This disturbance only extends a distance approx. A(exp 1/2) into the bulk material. A group of identical contacts will result in an excess temperature drop that scales as n(exp -1/2), where n is the number of contacts and n dot a is constant. This implies that flat rough surfaces will have a lower excess temperature drop than flat polished surfaces.

  13. Determinaion of Oligo-λ-carrageenans by reversed phase ion-pair high-performance liquid chromatography coupled with electrospray Ionization-QqQ-Mass Spectrometry%离子对-反相高效液相色谱-三重四级杆质谱法测定λ-卡拉胶寡糖

    上官巧灵; 陈海敏; 陈娟娟; 严小军


    目的 建立离子对-反相高效液相色谱(RPIP-HPLC)和电喷雾离子源-三重四级杆质谱(ESI-QqQ-MS)联用技术快速分离鉴定多阴离子λ-卡拉胶寡糖的方法.方法 采用Hypersil GOLD C18色谱柱(100mm×2.1mm,3μm),流速0.2mL·min-1,柱温30℃,考察3种离子对试剂(庚胺、二丁胺、三丙胺)、不同离子对试剂浓度(3、5和8 mmol/L)及流动相pH值(pH4.5、5.5、6.5)对λ-卡拉胶寡糖分离效果的影响.结果 当流动相组成为5 mmol·L-1庚胺乙酸盐水溶液(pH5.5)和5 mmol·L-1庚胺乙酸盐甲醇溶液(pH 5.5)时,聚合度(DP)在2~15间的λ-卡拉胶寡糖分离效果较好,同时从相应的质谱数据中能准确获得各聚合度λ-卡拉胶寡糖的结构信息.结论 该方法能较好地分离并鉴定多阴离子λ-卡拉胶寡糖,所得寡糖质谱信息对λ-卡拉胶寡糖的结构解析有借鉴作用.%Objective An effective method,reversed phase ion pair high-performance liquid chromatography coupled with electrospray ionization QqQ mass spectrometry (RPIP-HPLC-ESI-QqQ-MS),was developed to separate and identify polyanionic λ-carrageenan oligosaccharides with different polymerization degree.Methods The Hypersil GOLD C18 column(100 mm×2.1 mm,3μm)was used to separate oligoλ-carrageenans.The flow rate was 0.2 mL · min-1 and the column temperature was 30℃.The separation conditions were optimized with different solvent systems in which the species and concentration of ion-pairing reagent and the pH of mobile phase were varied.The ion-pairing reagent was heptylammonium,dibutylammonium,tripropylammonium,respectively.Mass spectra were obtained synchronously by ESI-QqQ-MS in positive mode.Results Oligo-λ-carrageenans,of which the polymerization degree was between 2 to 15,were separated preferably by using MeOH/H2O with 5 mmol · L-1 heptylammonium acetate acid (adjusted to pH 5.5 with acetate acid) as eluent in linear gradient mode.The accurate structure information of these oligosaccharides

  14. Contact angle hysteresis explained.

    Gao, Lichao; McCarthy, Thomas J


    A view of contact angle hysteresis from the perspectives of the three-phase contact line and of the kinetics of contact line motion is given. Arguments are made that advancing and receding are discrete events that have different activation energies. That hysteresis can be quantified as an activation energy by the changes in interfacial area is argued. That this is an appropriate way of viewing hysteresis is demonstrated with examples.

  15. Introduction to contact mechanics

    Fischer-Cripps, Anthony C


    Contact mechanics deals with the elastic or plastic contact between two solid objects, and is thus intimately connected with such topics as fracture, hardness, and elasticity.This text, intended for advanced undergraduates, begins with an introduction to the mechanical properties of materials, general fracture mechanics, and fractures in brittle solids.This is followed by a detailed discussion of stresses and the nature of elastic and elastic-plastic contact.

  16. Allergic Contact Dermatitis

    Meltem Önder


    Full Text Available Allergic contact dermatitis is the delayed type hypersensitivity reaction to exogenous agents. Allergic contact dermatitis may clinically present acutely after allergen exposure and initial sensitization in a previously sensitized individual. Acute phase is characterized by erythematous, scaly plaques. In severe cases vesiculation and bullae in exposed areas are very characteristic. Repeated or continuous exposure of sensitized individual with allergen result in chronic dermatitis. Lichenification, erythematous plaques, hyperkeratosis and fissuring may develop in chronic patients. Allergic contact dermatitis is very common dermatologic problem in dermatology daily practice. A diagnosis of contact dermatitis requires the careful consideration of patient history, physical examination and patch testing. The knowledge of the clinical features of the skin reactions to various contactans is important to make a correct diagnosis of contact dermatitis. It can be seen in every age, in children textile product, accessories and touch products are common allergens, while in adults allergic contact dermatitis may be related with topical medicaments. The contact pattern of contact dermatitis depends on fashion and local traditions as well. The localization of allergic reaction should be evaluated and patients’ occupation and hobbies should be asked. The purpose of this review is to introduce to our collaques up dated allergic contact dermatitis literatures both in Turkey and in the World.

  17. Contact Quality in Participation

    Simonsen, Jesper; Jensen, Olav Storm


    We investigate the concept of participation from the perspective of quality of the contact in the communicative interactions between participants. We argue for the need for an academic-personal competence that qualifies the human contact central in all Participatory Design (PD) activities as a way...... to contribute to “an era of participation.” We describe a contact perspective in PD developed through a collaboration with body-oriented psychotherapeutic research that have specialized experiences in investigating open-minded contact and authentic meetings as body-related experiences....

  18. Colors and contact dermatitis.

    Bonamonte, Domenico; Foti, Caterina; Romita, Paolo; Vestita, Michelangelo; Angelini, Gianni


    The diagnosis of skin diseases relies on several clinical signs, among which color is of paramount importance. In this review, we consider certain clinical presentations of both eczematous and noneczematous contact dermatitis in which color plays a peculiar role orientating toward the right diagnosis. The conditions that will be discussed include specific clinical-morphologic subtypes of eczematous contact dermatitis, primary melanocytic, and nonmelanocytic contact hyperchromia, black dermographism, contact chemical leukoderma, and others. Based on the physical, chemical, and biologic factors underlying a healthy skin color, the various skin shades drawing a disease picture are thoroughly debated, stressing their etiopathogenic origins and histopathologic aspects.

  19. Sutures and contact homology I

    Colin, Vincent; Honda, Ko; Hutchings, Michael


    We define a relative version of contact homology for contact manifolds with convex boundary, and prove basic properties of this relative contact homology. Similar considerations also hold for embedded contact homology.

  20. Screw bondgraph contact dynamics

    Visser, Martijn; Stramigioli, Stefano; Heemskerk, Cock


    This paper presents an elegant contact dynamics model in screw bondgraph form. It can model the contact between any two objects of finite curvature. It does so by defining a Gauss frame on the surfaces of both objects in the points that are closest to each other. Then it describes how the Gauss fram

  1. Contact dermatitis. A review

    Andersen, Klaus Ejner; Benezra, C; Burrows, D;


    In recent years, there has been a dramatic rise in our understanding of contact dermatitis. This paper is a review of our knowledge of the mechanisms involved in contact dermatitis and related phenomena, the investigation of these events and the emergence of significant new allergens during...

  2. Allergic Contact Dermatitis

    Meltem Önder


    Allergic contact dermatitis is the delayed type hypersensitivity reaction to exogenous agents. Allergic contact dermatitis may clinically present acutely after allergen exposure and initial sensitization in a previously sensitized individual. Acute phase is characterized by erythematous, scaly plaques. In severe cases vesiculation and bullae in exposed areas are very characteristic. Repeated or continuous exposure of sensitized individual with allergen result in chronic dermatitis. Lichenific...

  3. Critical Points of Contact

    Jensen, Ole B.; Morelli, Nicola


    where the networks meet and establish contact. Thus we argue for the usefulness of the notion of Critical Point of Contact (CPC) to deepen our understanding of the actual life within networks. En route to this notion we draw upon theories within as diverse realms such as interaction design, service...

  4. Contact Hamiltonian mechanics

    Bravetti, Alessandro, E-mail: [Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, A. P. 70543, México, DF 04510 (Mexico); Cruz, Hans, E-mail: [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A. P. 70543, México, DF 04510 (Mexico); Tapias, Diego, E-mail: [Facultad de Ciencias, Universidad Nacional Autónoma de México, A.P. 70543, México, DF 04510 (Mexico)


    In this work we introduce contact Hamiltonian mechanics, an extension of symplectic Hamiltonian mechanics, and show that it is a natural candidate for a geometric description of non-dissipative and dissipative systems. For this purpose we review in detail the major features of standard symplectic Hamiltonian dynamics and show that all of them can be generalized to the contact case.

  5. Contact materials for nanoelectronics

    Alshareef, Husam N.


    In this article, we review current research activities in contact material development for electronic and nanoelectronic devices. A fundamental issue in contact materials research is to understand and control interfacial reactions and phenomena that modify the expected device performance. These reactions have become more challenging and more difficult to control as new materials have been introduced and as device sizes have entered the deep nanoscale. To provide an overview of this field of inquiry, this issue of MRS Bulletin includes articles on gate and contact materials for Si-based devices, junction contact materials for Si-based devices, and contact materials for alternate channel substrates (Ge and III-V), nanodevices. © 2011 Materials Research Society.

  6. Allergic contact dermatitis.

    Becker, Detlef


    Allergic contact dermatitis is a frequent inflammatory skin disease. The suspected diagnosis is based on clinical symptoms, a plausible contact to allergens and a suitable history of dermatitis. Differential diagnoses should be considered only after careful exclusion of any causal contact sensitization. Hence, careful diagnosis by patch testing is of great importance. Modifications of the standardized test procedure are the strip patch test and the repeated open application test. The interpretation of the SLS (sodium lauryl sulfate) patch test as well as testing with the patients' own products and working materials are potential sources of error. Accurate patch test reading is affected in particular by the experience and individual factors of the examiner. Therefore, a high degree of standardization and continuous quality control is necessary and may be supported by use of an online patch test reading course made available by the German Contact Dermatitis Research Group. A critical relevance assessment of allergic patch test reactions helps to avoid relapses and the consideration of differential diagnoses. Any allergic test reaction should be documented in an allergy ID card including the INCI name, if appropriate. The diagnostics of allergic contact dermatitis is endangered by a seriously reduced financing of patch testing by the German statutory health insurances. Restrictive regulations by the German Drug Law block the approval of new contact allergens for routine patch testing. Beside the consistent avoidance of allergen contact, temporary use of systemic and topical corticosteroids is the therapy of first choice.

  7. Ganymede's internal structure including thermodynamics of magnesium sulfate oceans in contact with ice

    Vance, Steve; Bouffard, Mathieu; Choukroun, Mathieu; Sotin, Christophe


    higher than 10 wt%. Flotation can occur over tens of kilometers of depth, indicating the possibility for upward ‘snow’ or other exotic modes of heat and material transport. We assess Ganymede's interior structure for oceans with magnesium sulfate. New activity models predict freezing of ice in magnesium sulfate solutions. High ocean salinities are permitted by constraints on Ganymede's sulfur content. Stability under high pressure ice implies water rock contact and layered oceans. Upward ‘snow’ of high-pressure ices occurs in the lower depths of salty oceans.

  8. Theoretical study on the reactivity of sulfate species with hydrocarbons

    Ma, Q.; Ellis, G.S.; Amrani, A.; Zhang, T.; Tang, Y.


    The abiotic, thermochemically controlled reduction of sulfate to hydrogen sulfide coupled with the oxidation of hydrocarbons, is termed thermochemical sulfate reduction (TSR), and is an important alteration process that affects petroleum accumulations in nature. Although TSR is commonly observed in high-temperature carbonate reservoirs, it has proven difficult to simulate in the laboratory under conditions resembling nature. The present study was designed to evaluate the relative reactivities of various sulfate species in order to provide greater insight into the mechanism of TSR and potentially to fill the gap between laboratory experimental data and geological observations. Accordingly, quantum mechanics density functional theory (DFT) was used to determine the activation energy required to reach a potential transition state for various aqueous systems involving simple hydrocarbons and different sulfate species. The entire reaction process that results in the reduction of sulfate to sulfide is far too complex to be modeled entirely; therefore, we examined what is believed to be the rate limiting step, namely, the reduction of sulfate S(VI) to sulfite S(IV). The results of the study show that water-solvated sulfate anions SO42 - are very stable due to their symmetrical molecular structure and spherical electronic distributions. Consequently, in the absence of catalysis, the reactivity of SO42 - is expected to be extremely low. However, both the protonation of sulfate to form bisulfate anions (HSO4-) and the formation of metal-sulfate contact ion-pairs could effectively destabilize the sulfate molecular structure, thereby making it more reactive. Previous reports of experimental simulations of TSR generally have involved the use of acidic solutions that contain elevated concentrations of HSO4- relative to SO42 -. However, in formation waters typically encountered in petroleum reservoirs, the concentration of HSO4- is likely to be significantly lower than the levels

  9. Colored Contact Lens Dangers

    Full Text Available ... about the members of the eye-care team . Consumer warning about the improper use of colored contact ... About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms of ...

  10. Colored Contact Lens Dangers

    Full Text Available ... Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without ... been properly fitted by an eye care professional, the lenses stuck to my eye like a suction ...

  11. Tomato contact dermatitis

    Paulsen, Evy; Christensen, Lars P; Andersen, Klaus Ejner


    The tomato plant (Solanum lycopersicum) is an important crop worldwide. Whereas immediate-type reactions to tomato fruits are well known, contact dermatitis caused by tomatoes or tomato plants is rarely reported. The aims of this study were to present new data on contact sensitization to tomato...... plants and review the literature on contact dermatitis caused by both plants and fruits. An ether extract of tomato plants made as the original oleoresin plant extracts, was used in aimed patch testing, and between 2005 and 2011. 8 of 93 patients (9%) tested positive to the oleoresin extracts....... This prevalence is in accordance with the older literature that reports tomato plants as occasional sensitizers. The same applies to tomato fruits, which, in addition, may cause protein contact dermatitis. The allergens of the plant are unknown, but both heat-stable and heat-labile constituents seem...

  12. Colored Contact Lens Dangers

    Full Text Available ... wear any kind of contact lens. In Butler's case, the lenses caused an infection and left her with a corneal abrasion. ... Studies Look at Effects of Marijuana on Vision FEB ...

  13. Colored Contact Lens Dangers

    Full Text Available ... lentes de contacto de color Sep. 26, 2013 It started as an impulsive buy from a souvenir ... Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored contact lenses without ...

  14. Colored Contact Lens Dangers

    Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms ...

  15. Contact Lens Risks

    ... Tap and distilled water have been associated with Acanthamoeba keratitis, a corneal infection that is resistant to ... to: Advice for Patients With Soft Contact Lenses: Acanthamoeba Keratitis Infections Related to Complete® MoisturePlus Multi Purpose ...

  16. Colored Contact Lens Dangers

    Full Text Available ... colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are ... from dry eye now have a completely new, drug-free alternative to lubricating eye drops and topical ...

  17. Colored Contact Lens Dangers

    Full Text Available ... shop, but 10 hours after she first put in a pair of colored contact lenses, Laura Butler of Parkersburg, W.Va., had "extreme pain in both eyes," she said. "Because I had not ...

  18. Colored Contact Lens Dangers

    Full Text Available ... be purchased over-the-counter or on the Internet," says Thomas Steinemann, MD, professor of ophthalmology at ... ask for a prescription. There is no such thing as a "one size fits all" contact lens. ...

  19. Colored Contact Lens Dangers

    Full Text Available ... also available in Spanish . Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical ...

  20. Fragrance allergic contact dermatitis.

    Cheng, Judy; Zug, Kathryn A


    Fragrances are a common cause of allergic contact dermatitis in Europe and in North America. They can affect individuals at any age and elicit a spectrum of reactions from contact urticaria to systemic contact dermatitis. Growing recognition of the widespread use of fragrances in modern society has fueled attempts to prevent sensitization through improved allergen identification, labeling, and consumer education. This review provides an overview and update on fragrance allergy. Part 1 discusses the epidemiology and evaluation of suspected fragrance allergy. Part 2 reviews screening methods, emerging fragrance allergens, and management of patients with fragrance contact allergy. This review concludes by examining recent legislation on fragrances and suggesting potential additions to screening series to help prevent and detect fragrance allergy.

  1. Colored Contact Lens Dangers

    Full Text Available ... Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms of Service For Advertisers For Media Ophthalmology ...

  2. Colored Contact Lens Dangers

    Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... 2016 More Eye Health News Studies Look at Effects of Marijuana on Vision FEB 28, 2017 By ...

  3. Colored Contact Lens Dangers

    Full Text Available ... Contact Lens-Related Eye Infections Mar 01, 2017 New Technology Helps the Legally Blind Be More Independent ... Worse? May 16, 2016 More Eye Health News New Dry Eye Treatment is a Tear-Jerker JUL ...

  4. Colored Contact Lens Dangers

    ... Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Sep. 26, 2013 It started ...

  5. Colored Contact Lens Dangers

    Full Text Available ... Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados con los ... contacto de color Sep. 26, 2013 It started as an impulsive buy from a souvenir shop, but ...

  6. Colored Contact Lens Dangers

    Full Text Available ... Healthy Contact Lens Use May 31, 2016 Is El Niño Making Your Allergies Worse? May 16, 2016 ... Number: * Email: * Enter code: * Message: Thank you Your feedback has been sent.

  7. Colored Contact Lens Dangers

    Full Text Available ... Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without ... been properly fitted by an eye care professional, the lenses stuck to my eye like a suction ...

  8. Pediatric contact dermatitis

    Sharma Vinod; Asati Dinesh


    Allergic contact dermatitis (ACD) in children, until recently, was considered rare. ACD was considered as a disorder of the adult population and children were thought to be spared due to a lack of exposure to potential allergens and an immature immune system. Prevalence of ACD to even the most common allergens in children, like poison ivy and parthenium, is relatively rare as compared to adults. However, there is now growing evidence of contact sensitization of the pediatric population, and i...

  9. Contact air abrasion.

    Porth, R


    The advantages of contact air abrasion techniques are readily apparent. The first, of course, is the greatly increased ease of use. Working with contact also tends to speed the learning curve by giving the process a more natural dental feel. In addition, as one becomes familiar with working with a dust stream, the potential for misdirecting the air flow is decreased. The future use of air abrasion for deep decay removal will make this the treatment of choice for the next millennium.

  10. 并联式双梯度反相离子对液相色谱法快速检测土壤中芳磺酸%The Rapid Detection of Seven Kinds of Aromatic Sulfonic Acid in Soil by Parallel and Dual Ion-Pair RP-HPLC Gradient Elution Method

    杨柳; 马浩; 李桂香; 贺伟; 施超欧


    Established a method for extraction and fast detection of 7 kinds of aromatic sulfonic acid ( anthraquinone 1, 5-disulfonic acid, 1-amino-8-naphthol-3, 6-disulfonic acid, 1-naphthol-4-sulfonic, anthraquinone-1, 8-disulfonic acid, 1-naphthalene sulfonic acid, 2-naphthalene sulfonic acid, 3-hydroxy-2-naphthoic acid) in soil by valve switching Ion-pair RP-HPLC with a dual system. Two columns were used in this system. When one was in the process of determination, the other one was in the process of equilibration. Thus 38�5% time was saved. Analytical columns were Dikma Diamonsil C18 (150 mm × 4�6 mm × 5 μm) , eluents were ion-pair reagent ( Tetrabutylammonium Hydrogen Sulfate ) and acetonitrile, and wave lengths were 226, 235, 258 nm. A good linear relationship was obtained for each aromatic sulfonic acid. All linear correlation coefficients were more than 0�999 9. Extracted and detected the randomly selected samples, and got each RSD of the 7 compounds less than 7% as well as the quantification limit no more than 0�181 2 μg/g. Both of the repeatability and quantification limit meet the requirements of detection.%通过阀切换并联式双系统,建立了一套测定土壤样品中7种芳磺酸的反相离子对液相色谱法。该方法采用2根色谱柱,一根色谱柱分析的同时,另一根色谱柱通过阀切换实现平衡,节约了38�5%的分析时间。方法使用 Dikma Diamonsil C18(150 mm ×4�6 mm ×5μm)色谱柱,以离子对试剂(四丁基硫酸氢铵)和乙腈为流动相,检测波长为226、235、258 nm。各组分线性关系良好,线性相关系数均在0�9999以上。随机抽取样品进行重新提取、检测,得到各组分的相对标准偏差均小于7%,且定量限最高不超过0�1812μg/g,重复性和定量限均能满足实验要求。

  11. Double pendulum contact problem

    Špička J.


    Full Text Available The work concerns contact problems focused on biomechanical systems modelled by a multibody approach. The example is modelling of impact between a body and an infrastructure. The paper firstly presents algorithm for minimum distance calculation. An analytical approach using a tangential plain perpendicular to an initial one is applied. Contact force generated during impact is compared by three different continuous force models, namely the Hertz’s model, the spring-dashpot model and the non-linear damping model. In order to identify contact parameters of these particular models, the method of numerical optimization is used. Purpose of this method is to find the most corresponding results of numerical simulation to the original experiment. Numerical optimization principle is put upon a bouncing ball example for the purpose of evaluation of desirable contact force parameters. The contact modelling is applied to a double pendulum problem. The equation of motion of the double pendulum system is derived using Lagrange equation of the second kind with multipliers, respecting the contact phenomena. Applications in biomechanical research are hinted at arm gravity motion and a double pendulum impact example.

  12. Patients with multiple contact allergies

    Carlsen, Berit Christina; Andersen, Klaus Ejner; Menné, Torkil;


    Patients with multiple contact allergies, also referred to as polysensitized, are more frequent than predicted from prevalence of single sensitivities. The understanding of why some people develop multiple contact allergies, and characterization of patients with multiple contact allergies...... of developing multiple contact allergies. Evidence of allergen clusters among polysensitized individuals is also reviewed. The literature supports the idea that patients with multiple contact allergies constitute a special entity within the field of contact allergy. There is no generally accepted definition...... of patients with multiple contact allergies. We suggest that contact allergy to 3 or more allergens are defined as multiple contact allergies....

  13. Determinação turbidimétrica do antidepressivo amitriptilina em sistema fia explorando a formação do par iônico com lauril sulfato de sódio Turbidimetric determination of antidepressant amitriptyline in fia system exploiting the ion-pair formation with sodium lauryl sulphate

    Gustavo Silveira


    Full Text Available The present work purposes the development of an analytical method for amitriptyline determination in pharmaceutical formulations using FIA system. It was based on interaction of amitriplyline with sodium lauryl sulphate in acid medium (pH 2.5 resulting in the ion-pair formation turbidimetrically detected at 410 nm. The fitting regression equation for range curve from 2.0 x 10-3 up to 3.2 x 10-3 mol L-1 was found to be analytical signal = -2.7417 + 0.1538 [amitriptyline] (r = 0.99991 with a detection limit of 1.8 x 10-3 mol L-1. The precision assessed as relative standard deviation (n = 10 was found to be 2.40 and 1.94%, for the respective concentration of amitriplyline 2.0 x 10-3 and 3.2 x 10-3 mol L-1 and the sample throughout was 60 h-1. The accuracy of method was successfully assessed in pharmaceutical formulation after comparison with a reference analytical method.

  14. Rough Surface Contact

    T Nguyen


    Full Text Available This paper studies the contact of general rough curved surfaces having nearly identical geometries, assuming the contact at each differential area obeys the model proposed by Greenwood and Williamson. In order to account for the most general gross geometry, principles of differential geometry of surface are applied. This method while requires more rigorous mathematical manipulations, the fact that it preserves the original surface geometries thus makes the modeling procedure much more intuitive. For subsequent use, differential geometry of axis-symmetric surface is considered instead of general surface (although this “general case” can be done as well in Chapter 3.1. The final formulas for contact area, load, and frictional torque are derived in Chapter 3.2.

  15. Acrylate Systemic Contact Dermatitis.

    Sauder, Maxwell B; Pratt, Melanie D


    Acrylates, the 2012 American Contact Dermatitis Society allergen of the year, are found in a range of products including the absorbent materials within feminine hygiene pads. When fully polymerized, acrylates are nonimmunogenic; however, if not completely cured, the monomers can be potent allergens.A 28-year-old woman is presented, who had her teeth varnished with Isodan (Septodont, Saint-Maur-des-Fossés, France) containing HEMA (2-hydroxyethyl methacrylate) with no initial reaction. Approximately 1 month later, the patient developed a genital dermatitis secondary to her feminine hygiene pads. The initial reaction resolved, but 5 months later, the patient developed a systemic contact dermatitis after receiving a second varnishing.The patient was dramatically patch test positive to many acrylates. This case demonstrates a reaction to likely unpolymerized acrylates within a feminine hygiene pad, as well as broad cross-reactivity or cosensitivity to acrylates, and possibly a systemic contact dermatitis with systemic re-exposure to unpolymerized acrylates.

  16. Shoe allergic contact dermatitis.

    Matthys, Erin; Zahir, Amir; Ehrlich, Alison


    Foot dermatitis is a widespread condition, affecting men and women of all ages. Because of the location, this condition may present as a debilitating problem to those who have it. Allergic contact dermatitis involving the feet is frequently due to shoes or socks. The allergens that cause shoe dermatitis can be found in any constituent of footwear, including rubber, adhesives, leather, dyes, metals, and medicaments. The goal of treatment is to identify and minimize contact with the offending allergen(s). The lack of product information released from shoe manufacturers and the continually changing trends in footwear present a challenge in treating this condition. The aim of this study is to review the current literature on allergic contact shoe dermatitis; clinical presentation, allergens, patch testing, and management will be discussed. PubMed and MEDLINE databases were used for the search, with a focus on literature updates from the last 15 years.


    Trisna Yuliharti Tersinanda


    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE Allergic contact dermatitis is an immunologic reaction that tends to involve the surrounding skin and may even spread beyond affected sites. This skin disease is one of the more frequent, and costly dermatologic problems. Recent data from United Kingdom and United States suggest that the percentage of occupational contact dermatitis due to allergy may be much higher, thus raising the economic impact of occupational allergic contact dermatitis. There is not enough data about the epidemiology of allergic contact dermatitis in Indonesia, however based on research that include beautician in Denpasar, about 27,6 percent had side effect of cosmetics, which is 25,4 percent of it manifested as allergic contact dermatitis. Diagnosis of allergic contact dermatitis is based on anamnesis, physical examination, patch test, and this disease should be distinguished from other eczematous skin disease. The management is prevention of allergen exposure, symptomatic treatment, and physicochemical barrier /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

  18. Allergic contact dermatitis.

    Gober, Michael D; Gaspari, Anthony A


    Allergic contact dermatitis is a classic example of a cell mediated hypersensitivity reaction in the skin. This occurs as a result of xenobiotic chemicals penetrating into the skin, chemically reacting with self proteins, eventually resulting in a hapten-specific immune response. It is precisely because of this localized immune response that allergic signs and symptoms occur (redness, edema, warmth and pruritus). It has been known for years that conventional T-cells (CD4+ or CD8+ T-cells that express a T-cell receptor alpha/Beta) are critical effectors for this reaction. There is emerging evidence that innate immune lymphocytes such as invariant Natural killer T-cells and even Natural killer cells may play important role. Other T-cell types such as Tregulatory cells and the IL-10 secreting Tregulatory cells type I are likely to be important in the control (resolution) of allergic contact dermatitis. Other cell types that may contribute include B-cells and hapten-specific IgM. Additionally, epidermal Langerhans cells have been ascribed an indispensable role as an antigen presenting cell to educate T-cells of the skin immune system. Studies of mice that lack this cell type suggest that Langerhans cells may be dispensible, and may even play a regulatory role in allergic contact dermatitis. The identity of the antigen presenting cells that complement Langerhans cells has yet to be identified. Lastly, Keratinocytes play a role in all phases of allergic contact dermatitis, from the early initiation phase with the elaboration of inflammatory cytokines, that plays a role in Langerhans cell migration, and T-cell trafficking, through the height of the inflammatory phase with direct interactions with epidermotrophic T-cells, through the resolution phase of allergic contact dermatitis with the production of anti-inflammatory cytokines and tolerogenic antigen presentation to effector T-cells. As the understanding of allergic contact dermatitis continues to improve, this will

  19. Psoriasis and Contact Sensitivitiy

    Deniz Arlı


    Full Text Available Objective: The aim of this study was to investigate the frequency of contact sensitivity in patients with psoriasis, whether there was an association between clinical types and contact sensitivity, whether patch test is a factor that causes Koebner reaction and frequency of contact sensitivity against commonly used topical corticosteroids. Methods: Fifty patients with psoriasis and 50 healthy volunteers were included in this study and ‘European standard series' and test units of active ingredients of some corticosteroids were performed on their upper back. The patches were read on hours 24, 48 and on day 7 in order to detect delayed allergic reactions and also Koebner reaction. The results of both groups were compared by using chi-square test. Results: At the end of the patch test allergic reaction was observed in 7 of 50 (14% patients with psoriasis and 12 of 50 (24% healthy volunteers. There was no statistically significant difference between allergic reaction of study group and healthy volunteers. There was no statistically significant difference between the clinical types of psoriasis and allergic contact sensitivity. The frequency of reaction increased in individuals having a positive sensitivity history to any substance in both patient and control groups. Reaction to topical steroids was not seen in any patients. Koebner phenomenon due to patch test was also not seen in any patients. Conclusion: We did not show any association between psoriasis and contact sensitivity in this study. We believe that contact allergens should be determined by using patch test in psoriatic patients with a positive history to any substance.

  20. Charge inversion and ion-ion correlation effects at the mercury/aqueous MgSO4 interface: Toward the solution of a long-standing issue

    Wennersson, E.; Kjellander, R.; Lyklema, J.


    Charge inversion is the phenomenon in which an electric double layer contains more counterions than needed to compensate the surface charge. For colloidal particles this has the consequence that the apparent surface charge, as inferred from electrophoresis or interaction studies, has a sign opposite

  1. Screening genetically diverse pear species for in vitro CaCl2, MgSO4 and KH2PO4 requirements

    Conservation of important plant germplasm is often difficult due to the specific growth requirements of genetically diverse species. This also applies to in vitro culture collections where a wide range of plants may have suboptimal growth or remain recalcitrant to growth on standard media. A series ...

  2. Critical Points of Contact

    Jensen, Ole B.; Morelli, Nicola


    where the networks meet and establish contact. Thus we argue for the usefulness of the notion of Critical Point of Contact (CPC) to deepen our understanding of the actual life within networks. En route to this notion we draw upon theories within as diverse realms such as interaction design, service...... design, geography, and mobility studies. After the introduction in section we develop and define the notion of CPC based upon a broad set of disciplines and theories. We illustrate the usefulness of the notion within the field of mobility in the network city and within the field of service design...

  3. Ion-Pair States in Triplet Molecular Hydrogen

    Setzer, W.; Baker, B. C.; Ashman, S.; Morgan, T. J.


    An experimental search is underway to observe the long range triplet ionic states H+ H- of molecular hydrogen. Resonantly enhanced multi-photon ionization of the metastable c 3∏u- 2 pπ state is used access to the R(1)nd1 n = 21 Rydberg state that serves as an intermediate stepping stone state to probe the energy region above the ionization limit with a second tunable laser photon. The metastable state is prepared by electron capture of 6 keV H2+ions in potassium in a molecular beam. Formation of the H+ H- triplet configuration involves triplet excited states of the H- ion, especially the 2p23Pe state, the second bound state of H- predicted to exist with a lifetime long compared to typical auto ionization lifetimes but not yet observed experimentally. Details of the experiment and preliminary results to date will be presented at the conference.

  4. Colored Contact Lens Dangers

    ... Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms of Service For Advertisers For Media Ophthalmology Job Center © American Academy of ...

  5. Lubrication Of Nonconformal Contacts

    Jeng, Yeau-Ren


    Report discusses advances in knowledge of lubrication of nonconformal contacts in bearings and other machine elements. Reviews previous developments in theory of lubrication, presents advances in theory of lubrication to determine minimum film thickness, and describes experiments designed to investigate one of regimes of lubrication for ball bearings.

  6. [Contact allergies in musicians].

    Gasenzer, E R; Neugebauer, E A M


    During the last years, the problem of allergic diseases has increased. Allergies are errant immune responses to a normally harmless substance. In musicians the allergic contact dermatitis to exotic woods is a special problem. Exotic rosewood contains new flavonoids, which trigger an allergic reaction after permanent contact with the instrument. High quality woodwind instruments such as baroque flute or clarinets are made in ebony or palisander because of its great sound. Today instruments for non-professional players are also made in these exotic materials and non-professionals may have the risk to develop contact dermatitis, too. Brass-player has the risk of an allergic reaction to the different metals contained in the metal sheets of modern flutes and brass instruments. Specially nickel and brass alloys are used to product flute tubes or brass instruments. Special problem arises in children: patients who are allergic to plants or foods have a high risk to develop contact dermatitis. Parents don't know the materials of low-priced instruments for beginners. Often unknown cheap woods from exotic areas are used. Low-priced brass instruments contain high amount of brass and other cheap metals. Physicians should advice musician-patients or parents about the risks of the different materials and look for the reason of eczema on mouth, face, or hands.

  7. Colored Contact Lens Dangers

    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / News Halloween Hazard: The Hidden Dangers ... Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados con los lentes de contacto de ...

  8. Irritant contact dermatitis.

    Ale, Iris S; Maibach, Howard I


    Irritant contact dermatitis (ICD) is the most common form of contact dermatitis. It represents the cutaneous response to the toxic/physical effects of a wide variety of environmental agents. Nowadays, it is recognized that irritancy does not represent a single monomorphous entity but rather a complex biologic syndrome with diverse pathophysiology and clinical manifestations. The clinical presentation is highly variable depending on several factors, including properties and strength of the irritant, dose, duration and frequency of exposure, environmental factors, and skin susceptibility. The pathophysiological mechanism depends on activation of the innate immune system and involves skin barrier disruption, cellular changes, and release of proinflammatory mediators that directly recruit and activate T lymphocytes. The diagnosis of irritant contact dermatitis is often clinical, and involves a comprehensive history and examination, as well as the exclusion of allergic contact dermatitis with patch testing. Recent advances in understanding the pathogenesis as well as better awareness of the clinical significance of ICD will lead to a improved care for our patients.

  9. Lettuce contact allergy

    Paulsen, Evy; Andersen, Klaus E


    Lettuce (Lactuca sativa L.) and its varieties are important vegetable crops worldwide. They are also well-known, rarely reported, causes of contact allergy. As lettuce allergens and extracts are not commercially available, the allergy may be underdiagnosed. The aims of this article are to present...

  10. [Current contact allergens].

    Geier, J; Uter, W; Lessmann, H; Schnuch, A


    Ever-changing exposure to contact allergens, partly due to statutory directives (e.g. nickel, chromate, methyldibromo glutaronitrile) or recommendations from industrial associations (e.g. hydroxyisohexyl 3-cyclohexene carboxaldehyde), requires on-going epidemiologic surveillance of contact allergy. In this paper, the current state with special focus in fragrances and preservatives is described on the basis of data of the Information Network of Departments of Dermatology (IVDK) of the year 2010. In 2010, 12,574 patients were patch tested in the dermatology departments belonging to the IVDK. Nickel is still the most frequent contact allergen. However the continuously improved EU nickel directive already has some beneficial effect; sensitization frequency in young women is dropping. In Germany, chromate-reduced cement has been in use now for several years, leading to a decline in chromate sensitization in brick-layers. Two fragrance mixes are part of the German baseline series; they are still relevant. The most important fragrances in these mixes still are oak moss absolute and hydroxyisohexyl 3-cyclohexene carboxaldehyde. However, in relation to these leading allergens, sensitization frequency to other fragrances contained in the mixes seems to be increasing. Among the preservatives, MCI/MI has not lost its importance as contact allergen, in contrast to MDBGN. Sources of MCI/MI sensitization obviously are increasingly found in occupational context. Methylisothiazolinone is a significant allergen in occupational settings, and less frequently in body care products.

  11. The Nuclear Contact Exists

    Hen, O; Piasetzky, E; Miller, G A; Sargsian, M M


    Many-body systems of strongly interacting Fermions are ubiquitous in nature, ranging from High-Tc superconductors and ultra-cold atomic gases to atomic nuclei and neutron stars. Theoretical predictions, recently verified by measurements on ultra-cold atomic gases, show that under certain conditions the universal behavior of systems composed of two kinds of fermions can be described using a single parameter, simply called the contact, which is a measure of the number of different-fermion pairs in close proximity. This paper discusses the relevance of the contact for very different systems: atomic nuclei, made of strongly-interacting neutrons and protons. Here we show that the high-momentum distributions of protons and neutrons in nuclei, dominated by correlated proton-neutron pairs mainly in a spin-triplet state, have the same momentum dependence as those of cold atoms, with a strength described by the contact. We use high-energy electron scattering data to extract a value for the nuclear contact consistent wi...

  12. Contact: Releasing the news

    Pinotti, Roberto

    The problem of mass behavior after man's future contacts with other intelligences in the universe is not only a challenge for social scientists and political leaders all over the world, but also a cultural time bomb as well. In fact, since the impact of CETI (Contact with Extraterrestrial Intelligence) on human civilization, with its different cultures, might cause a serious socio-anthropological shock, a common and predetermined worldwide strategy is necessary in releasing the news after the contact, in order to keep possible manifestations of fear, panic and hysteria under control. An analysis of past studies in this field and of parallel historical situations as analogs suggests a definite "authority crisis" in the public as a direct consequence of an unexpected release of the news, involving a devastating "chain reaction" process (from both the psychological and sociological viewpoints) of anomie and maybe the collapse of today's society. The only way to prevent all this is to prepare the world's public opinion concerning contact before releasing the news, and to develop a long-term strategy through the combined efforts of scientists, political leaders, intelligence agencies and the mass media, in order to create the cultural conditions in which a confrontation with ETI won't affect mankind in a traumatic way. Definite roles and tasks in this multi-level model are suggested.

  13. Colored Contact Lens Dangers

    Full Text Available ... to drive for eight weeks," she said. "I now live with a corneal scar, vision damage and a drooping eyelid." To safely wear costume contact lenses for Halloween or any time of year, follow these guidelines: Get an eye ...

  14. Thermal Contact Conductance

    Salerno, Louis J.; Kittel, Peter


    The performance of cryogenic instruments is often a function of their operating temperature. Thus, designers of cryogenic instruments often are required to predict the operating temperature of each instrument they design. This requires accurate thermal models of cryogenic components which include the properties of the materials and assembly techniques used. When components are bolted or otherwise pressed together, a knowledge of the thermal performance of such joints are also needed. In some cases, the temperature drop across these joints represents a significant fraction of the total temperature difference between the instrument and its cooler. While extensive databases exist on the thermal properties of bulk materials, similar databases for pressed contacts do not. This has often lead to instrument designs that avoid pressed contacts or to the over-design of such joints at unnecessary expense. Although many people have made measurements of contact conductances at cryogenic temperatures, this data is often very narrow in scope and even more often it has not been published in an easily retrievable fashion, if published at all. This paper presents a summary of the limited pressed contact data available in the literature.

  15. Language Contact and Bilingualism

    Appel, René; Muysken, Pieter


    What happens - sociologically, linguistically, educationally, politically - when more than one language is in regular use in a community? How do speakers handle these languages simultaneously, and what influence does this language contact have on the languages involved? Although most people in the w

  16. Colored Contact Lens Dangers

    Full Text Available ... person. Get follow up exams with your eye care provider. If you notice redness, swelling, excessive discharge, pain or discomfort from wearing contact lenses, remove the lenses and seek immediate medical attention from an ophthalmologist. Related resources: Learn how ...

  17. Contact allergy to cosmetics

    Held, E; Johansen, J D; Agner, T


    .4%) had doubtfully positive reaction(s) and 31 (5.8%) had irritant reaction(s). Skin-care products were tested most frequently and were also found to cause most positive, doubtfully positive and irritant reactions, 80% of the patients with positive reactions to their own products had no history of contact...

  18. Colored Contact Lens Dangers

    Full Text Available ... EyeSmart videos on your website . Printable posters . Promotional materials for eye health observances. EyeSmart resources are also available in Spanish . Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs ...

  19. Duality based contact shape optimization

    Vondrák, Vít; Dostal, Zdenek; Rasmussen, John


    An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization.......An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization....

  20. Electrical contacts principles and applications

    Slade, Paul G


    Covering the theory, application, and testing of contact materials, Electrical Contacts: Principles and Applications, Second Edition introduces a thorough discussion on making electric contact and contact interface conduction; presents a general outline of, and measurement techniques for, important corrosion mechanisms; considers the results of contact wear when plug-in connections are made and broken; investigates the effect of thin noble metal plating on electronic connections; and relates crucial considerations for making high- and low-power contact joints. It examines contact use in switch

  1. Allergic contact dermatitis in children.

    Fontana, E; Belloni Fortina, A


    Allergic contact dermatitis is an inflammatory skin disease (delayed type hypersensitivity reaction) that accounts for up to 20% of all childhood dermatitis. Allergic contact dermatitis represents a clinical manifestation of contact sensitization and usually occurs at skin sites that have come into contact with the allergen. The clinical features of allergic contact dermatitis are itchy eczematous lesions. Prevalence of contact sensitization varies between 27% and 96% of children with suspected contact dermatitis. The relationship between contact sensitization and atopic dermatitis has been widely discussed but only conflicting data have been reported. Epicutaneous patch testing is the gold standard for the diagnosis of allergic contact dermatitis. The most common allergens detected in children are: metals, topical medicaments, fragrances, and preservatives. The first line management of allergic contact dermatitis in children is to avoid the offending allergens identified with the patch test and a topical corticosteroid therapy.

  2. [Contact dermatitis from Agave americana].

    de la Cueva, Pablo; González-Carrascosa, Mateo; Campos, Minia; Leis, Vicente; Suárez, Ricardo; Lázaro, Pablo


    Numerous plant species and their derivatives can cause skin reactions through a variety of mechanisms: irritative contact dermatitis, allergic contact dermatitis, contact urticaria and photodermatitis. We present a case of irritative contact dermatitis after exposure to the sap of Agave americana. The skin symptoms in this case have only been described on rare occasions; although this condition usually presents with a papulovesicular rash, in this patient it appeared as purpuric lesions in the contact area.

  3. Contact of surfaces and contact characteristics of offset surfaces

    Lixin CAO; Hu GONG; Jian LIU


    Based on differential geometry, the contact problems of two surfaces are discussed in this paper. The relationship between the contact status of two sur-faces and that of offset surfaces are also analyzed. For a 5-axis NC machining, some research such as optimization of cutter location and calculation of the geometrical cusp height are important. The research results indicate that the relative normal curvature is an important geometrical invariant for describing the contact state of two surfaces. For point contact two surfaces, the calculation equation for the second order remained error is given. For line contact two surfaces, the condition of the second order line contact is that the principal directions and curvatures of the two surfaces are the same along the contact curve. If two surfaces keep the second order line contact, their two offset surfaces will also keep the second order line contact, and their third order remained errors are also uniform with that of the two offset surfaces.

  4. Contact Graph Routing

    Burleigh, Scott C.


    Contact Graph Routing (CGR) is a dynamic routing system that computes routes through a time-varying topology of scheduled communication contacts in a network based on the DTN (Delay-Tolerant Networking) architecture. It is designed to enable dynamic selection of data transmission routes in a space network based on DTN. This dynamic responsiveness in route computation should be significantly more effective and less expensive than static routing, increasing total data return while at the same time reducing mission operations cost and risk. The basic strategy of CGR is to take advantage of the fact that, since flight mission communication operations are planned in detail, the communication routes between any pair of bundle agents in a population of nodes that have all been informed of one another's plans can be inferred from those plans rather than discovered via dialogue (which is impractical over long one-way-light-time space links). Messages that convey this planning information are used to construct contact graphs (time-varying models of network connectivity) from which CGR automatically computes efficient routes for bundles. Automatic route selection increases the flexibility and resilience of the space network, simplifying cross-support and reducing mission management costs. Note that there are no routing tables in Contact Graph Routing. The best route for a bundle destined for a given node may routinely be different from the best route for a different bundle destined for the same node, depending on bundle priority, bundle expiration time, and changes in the current lengths of transmission queues for neighboring nodes; routes must be computed individually for each bundle, from the Bundle Protocol agent's current network connectivity model for the bundle s destination node (the contact graph). Clearly this places a premium on optimizing the implementation of the route computation algorithm. The scalability of CGR to very large networks remains a research topic

  5. 离子对色谱法研究吡咯并喹呤醌与D-丝氨酸反应的化学动力学%Study of chemical kinetics between pyrroloquinoline quinine and D-serine in body by ion-pair liquid chromatography

    周杏琴; 钦晓峰; 张建康; 曹国宪


    As a new neurotransmitter present in the glial cells, D-serine ( Dser) plays an important role in central nervous system diseases. Pyrroloquinoline quinine (PQQ) can promote the production of the nerve growth factor and has a protective effect on nerve injuries. The chemical kinetics of PQQ and Dser was studied by determining the free contents of PQQ using ion-pair liquid chromatography (LC) , so it can provide important information for the mechanisms of PQQ in the regulation of neurotransmitter. The PQQ and the production of the incubation were separated on an Amethyst C18-P column using tetrabutylammonium bromide as ion-pair reagent. The average recoveries were between 94. 2% and 99. 3%, and the relative standard deviations were between 1. 05% and 2. 03%. The average rate constants (K) of PQQ with Dser were 0. 032, 0. 07 and 0. 17 h-1 at 25, 37 and 50 ℃ , respectively. The average activation energy (Ea) was 54. 7 Kj/mol. The values of half life (t1/2) were 22. 0, 9. 8 and 3. 99 h at 25, 37 and 50 ℃, respectively. The results showed that PQQ can regulate the balance of Dser in the brain. The method is simple and reliable.%D-丝氨酸(DSer)作为一种新的神经递质存在于胶质细胞,在中枢神经系统疾病中发挥重要的作用;吡咯并喹呤醌(PQQ)能够促进神经因子的产生和神经保护作用.采用离子对色谱法测定吡咯并喹呤醌(PQQ)与DSer反应中游离PQQ的浓度,通过化学反应动力学研究PQQ与DSer的作用,为PQQ在神经递质的调节作用机制提供重要的信息.采用四丁基溴化铵为离子对试剂,PQQ与DSer孵育反应后各物质在Amethyst C18-P柱上的分离度较好,平均回收率为94.2%~99.3%,相对标准偏差为1.05%~2.03%.PQQ-DSer反应的平均速率常数分别为0.032 h -( 25℃)、0.07 h-1 (37℃)、0.17 h-1(50℃);平均反应活化能为54.7 kJ/mol;半衰期分别为22.0 h(25℃)、9.8 h(37℃)和3.99 h(50℃).动力学结果显示PQQ对脑内DSer的平衡具有

  6. Reversed-phase ion-pair chromatography method for the determination of three water soluble vitamins in compound vitamin tablets%反相离子对色谱法测定复方维生素片中3种水溶性维生素的含量

    贺霞; 史朝晖; 刘慧; 张小岭; 闫笑笑; 周晓星; 王东凯


    Objective: To establish an ion-pair reversed-phase chromatographic method for the determination of vitamin B1, B2 and B6 in compound vitamin tablets. Methods: The contents of vitamin B1, B2 and B6 were simultaneously determined by ion-pair reversed-phase high performance liquid chromatography. Results: The linear ranges of vitamin B1, B2 and B6 were 6.3~14.7 μg· mL-1 ( r = 0. 999 60) , 7. 2 ~ 16. 8 μg·mL-1 ( r = 0. 999 1 ) and 6.3~14. 7 μg·mL-1(r =0. 999 2) with the average recoveries of 100. 08% (RSD=0.84%, n=9), 100.35% ( RSD = 1. 26% , n = 9 ) and 99. 41 % ( RSD = 1.10%, n = 9 ) , respectively. Conclusion: The method is simple, rapid, accurate and reliable, and can be used for the assay and quality control of compound vitamin tablets.%目的:建立反相离子对色谱法测定复方维生素片中维生素B1、维生素B2、维生素B6含量的方法.方法:以已烷磺酸钠作为离子对试剂,采用Diamonsil C18(250 mm×4.6mm,5μm)柱,同时测定复方维生素片中维生素B1、B2和B6的含量.结果:维生素B1、B2和B6分别在6.3 ~14.7 μg·mL-1(r=0.9998),7.2 ~ 16.8 μg·mL-1(r =0.9995),6.3 ~14.7 μg·mL-1(r=0.9996)范围内线性关系良好,平均回收率分别为100.08%(RSD =0.84%,n=9),100.35%(RSD=1.26%,n=9),99.41%(RSD=1.10%,n=9).结论:本方法快速、简便、准确,分离效果好,辅料无干扰,可用于该类制剂中维生素B1,B2和B6的含量测定及质量控制研究.

  7. /Au Back Contacts

    Paudel, Naba R.; Compaan, Alvin D.; Yan, Yanfa


    We report on the fabrication and characterization of CdTe thin-film solar cells with Cu-free MoO3- x /Au back contacts. CdTe solar cells with sputtered CdTe absorbers of thicknesses from 0.5 to 1.75 μm were fabricated on Pilkington SnO2:F/SnO2-coated soda-lime glasses coated with a 60- to 80-nm sputtered CdS layer. The MoO3- x /Au back contact layers were deposited by thermal evaporation. The incorporation of MoO3- x layer was found to improve the open circuit voltage ( V OC) but reduce the fill factor of the ultrathin CdTe cells. The V OC was found to increase as the CdTe thickness increased.

  8. Contact stress sensor

    Kotovsky, Jack [Oakland, CA


    A contact stress sensor includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a thermal compensator and a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  9. Occupational protein contact dermatitis.

    Barbaud, Annick; Poreaux, Claire; Penven, Emmanuelle; Waton, Julie


    Occupational contact dermatitis is generally caused by haptens but can also be induced by proteins causing mainly immunological contact urticaria (ICU); chronic hand eczema in the context of protein contact dermatitis (PCD). In a monocentric retrospective study, from our database, only 31 (0.41%) of patients with contact dermatitis had positive skin tests with proteins: 22 had occupational PCD, 3 had non-occupational PCD, 5 occupational ICU and 1 cook had a neutrophilic fixed food eruption (NFFE) due to fish. From these results and analysis of literature, the characteristics of PCD can be summarized as follows. It is a chronic eczematous dermatitis, possibly exacerbated by work, suggestive if associated with inflammatory perionyxix and immediate erythema with pruritis, to be investigated when the patient resumes work after a period of interruption. Prick tests with the suspected protein-containing material are essential, as patch tests have negative results. In case of multisensitisation revealed by prick tests, it is advisable to analyse IgE against recombinant allergens. A history of atopy, found in 56 to 68% of the patients, has to be checked for. Most of the cases are observed among food-handlers but PCD can also be due to non-edible plants, latex, hydrolysed proteins or animal proteins. Occupational exposure to proteins can thus lead to the development of ICU. Reflecting hypersensitivity to very low concentrations of allergens, investigating ICU therefore requires caution and prick tests should be performed with a diluted form of the causative protein-containing product. Causes are food, especially fruit peel, non-edible plants, cosmetic products, latex, animals.

  10. Contact stress sensor

    Kotovsky, Jack


    A method for producing a contact stress sensor that includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  11. Pediatric contact dermatitis.

    Sharma, Vinod K; Asati, Dinesh P


    Allergic contact dermatitis (ACD) in children, until recently, was considered rare. ACD was considered as a disorder of the adult population and children were thought to be spared due to a lack of exposure to potential allergens and an immature immune system. Prevalence of ACD to even the most common allergens in children, like poison ivy and parthenium, is relatively rare as compared to adults. However, there is now growing evidence of contact sensitization of the pediatric population, and it begins right from early childhood, including 1-week-old neonates. Vaccinations, piercing, topical medicaments and cosmetics in younger patients are potential exposures for sensitization. Nickel is the most common sensitizer in almost all studies pertaining to pediatric contact dermatitis. Other common allergens reported are cobalt, fragrance mix, rubber, lanolin, thiomersol, neomycin, gold, mercapto mix, balsum of Peru and colophony. Different factors like age, sex, atopy, social and cultural practices, habit of parents and caregivers and geographic changes affect the patterns of ACD and their variable clinical presentation. Patch testing should be considered not only in children with lesions of a morphology suggestive of ACD, but in any child with dermatitis that is difficult to control.

  12. Pediatric contact dermatitis

    Sharma Vinod


    Full Text Available Allergic contact dermatitis (ACD in children, until recently, was considered rare. ACD was considered as a disorder of the adult population and children were thought to be spared due to a lack of exposure to potential allergens and an immature immune system. Prevalence of ACD to even the most common allergens in children, like poison ivy and parthenium, is relatively rare as compared to adults. However, there is now growing evidence of contact sensitization of the pediatric population, and it begins right from early childhood, including 1-week-old neonates. Vaccinations, piercing, topical medicaments and cosmetics in younger patients are potential exposures for sensitization. Nickel is the most common sensitizer in almost all studies pertaining to pediatric contact dermatitis. Other common allergens reported are cobalt, fragrance mix, rubber, lanolin, thiomersol, neomycin, gold, mercapto mix, balsum of Peru and colophony. Different factors like age, sex, atopy, social and cultural practices, habit of parents and caregivers and geographic changes affect the patterns of ACD and their variable clinical presentation. Patch testing should be considered not only in children with lesions of a morphology suggestive of ACD, but in any child with dermatitis that is difficult to control.

  13. Dual contact pogo pin assembly

    Hatch, Stephen McGarry


    A contact assembly includes a base and a pair of electrical contacts supported by the base. A first end of the first electrical contact corresponds to a first end of the base and is configured to engage a first external conductive circuit element. A first end of the second electrical contact also corresponds to the first end of the base and is configured to engage a second external conductive circuit element. The first contact and the second contact are electrically isolated from one another and configured to compress when engaging an external connector element. The base includes an aperture positioned on a second end of the base outboard of a second end of the first and second electrical contacts. The aperture presents a narrowing shape with a wide mouth distal the electrical contacts and a narrow internal through-hole proximate the electrical contacts.

  14. Mechanical Contact Experiments and Simulations

    Nielsen, Chris Valentin; Martins, P; Zhang, W.


    geometries and different materials are analyzed including contact between dissimilar materials. The numerical implementation is performed with a finite element computer program based on the irreducible flow formulation, and contact between deformable objects is modelled by applying the penalty method....... The overall investigation serves for testing and validating the numerical implementation of the mechanical contact, which is one of the main contributions to a system intended for 3D simulation of resistance welding. Correct modelling of contact between parts to be welded, as well as contact with electrodes......, is crucial for satisfactory modelling of the resistance welding process. The resistance heating at the contact interfaces depends on both contact area and pressure, and as the contact areas develop dynamically, the presented tests are relevant for assessing the validity and accuracy of the mechanical contact...

  15. Contextualizing Intergroup Contact: Do Political Party Cues Enhance Contact Effects?

    Sønderskov, Kim Mannemar; Thomsen, Jens Peter Frølund


    political parties on us-them categorizations heightens the awareness of group memberships. This focus in turn enhances the positive intergroup contact effect by stimulating majority members to perceive contacted persons as prototypical outgroup members. A multilevel analysis of 22 countries and almost 37......,000 individuals confirms that the ability of intergroup contact to reduce antiforeigner sentiment increases when political parties focus intensively on immigration issues and cultural differences. Specifically, both workplace contact and interethnic friendship become more effective in reducing antiforeigner...

  16. Contact dermatitis in Nigeria.

    Olumide, Y M


    Nickel is the most important sensitizer in Lagos, with an incidence of 12.3% of 453 patients tested. There was no sex difference, as the wearing of necklaces and bracelets was equally fashionable among both sexes. Housewife eczema is not common, probably because of hardening. Dermatitis from additives in the processing of leather and rubber footwear was the next most common. Chromate sensitivity comes usually from leather or cement. Cultural and climatic factors are mainly responsible for differences in the incidence of contact dermatitis found in Lagos from other countries.

  17. Contact Control, Version 1


    The contact control code is a generalized force control scheme meant to interface with a robotic arm being controlled using the Robot Operating System (ROS). The code allows the user to specify a control scheme for each control dimension in a way that many different control task controllers could be built from the same generalized controller. The input to the code includes maximum velocity, maximum force, maximum displacement, and a control law assigned to each direction and the output is a 6 degree of freedom velocity command that is sent to the robot controller.

  18. Thermal contact conductance

    Madhusudana, Chakravarti V


    The work covers both theoretical and practical aspects of thermal contact conductance. The theoretical discussion focuses on heat transfer through spots, joints, and surfaces, as well as the role of interstitial materials (both planned and inadvertent). The practical discussion includes formulae and data that can be used in designing heat-transfer equipment for a variety of joints, including special geometries and configurations. All of the material has been updated to reflect the latest advances in the field.

  19. Contact dermatitis to methylisothiazolinone*

    Scherrer, Maria Antonieta Rios; Rocha, Vanessa Barreto; Andrade, Ana Regina Coelho


    Methylisothiazolinone (MI) is a preservative found in cosmetic and industrial products. Contact dermatitis caused by either methylchloroisothiazolinone/methylisothiazolinone (MCI/MI or Kathon CG) or MI has shown increasing frequency. The latter is preferably detected through epicutaneous testing with aqueous MI 2000 ppm, which is not included in the Brazilian standard tray. We describe a series of 23 patients tested using it and our standard tray. A case with negative reaction to MCI/MI and positive to MI is emphasized. PMID:26734880

  20. Adhesion in hydrogel contacts

    Torres, J. R.; Jay, G. D.; Kim, K.-S.; Bothun, G. D.


    A generalized thermomechanical model for adhesion was developed to elucidate the mechanisms of dissipation within the viscoelastic bulk of a hyperelastic hydrogel. Results show that in addition to the expected energy release rate of interface formation, as well as the viscous flow dissipation, the bulk composition exhibits dissipation due to phase inhomogeneity morphological changes. The mixing thermodynamics of the matrix and solvent determines the dynamics of the phase inhomogeneities, which can enhance or disrupt adhesion. The model also accounts for the time-dependent behaviour. A parameter is proposed to discern the dominant dissipation mechanism in hydrogel contact detachment.

  1. Allergic contact dermatitis from octylisothiazolinone

    Mose, Anja Pahlow; Frost, Simon; Ohlund, Ulf;


    Octylisothiazolinone is a biocide that has been reported as a moderate, but rare contact allergen.......Octylisothiazolinone is a biocide that has been reported as a moderate, but rare contact allergen....

  2. Contact Center Manager Administration (CCMA)

    Social Security Administration — CCMA is the server that provides a browser-based tool for contact center administrators and supervisors. It is used to manage and configure contact center resources...

  3. Optimal contact definition for reconstruction of Contact Maps

    Stehr Henning


    Full Text Available Abstract Background Contact maps have been extensively used as a simplified representation of protein structures. They capture most important features of a protein's fold, being preferred by a number of researchers for the description and study of protein structures. Inspired by the model's simplicity many groups have dedicated a considerable amount of effort towards contact prediction as a proxy for protein structure prediction. However a contact map's biological interest is subject to the availability of reliable methods for the 3-dimensional reconstruction of the structure. Results We use an implementation of the well-known distance geometry protocol to build realistic protein 3-dimensional models from contact maps, performing an extensive exploration of many of the parameters involved in the reconstruction process. We try to address the questions: a to what accuracy does a contact map represent its corresponding 3D structure, b what is the best contact map representation with regard to reconstructability and c what is the effect of partial or inaccurate contact information on the 3D structure recovery. Our results suggest that contact maps derived from the application of a distance cutoff of 9 to 11Å around the Cβ atoms constitute the most accurate representation of the 3D structure. The reconstruction process does not provide a single solution to the problem but rather an ensemble of conformations that are within 2Å RMSD of the crystal structure and with lower values for the pairwise average ensemble RMSD. Interestingly it is still possible to recover a structure with partial contact information, although wrong contacts can lead to dramatic loss in reconstruction fidelity. Conclusions Thus contact maps represent a valid approximation to the structures with an accuracy comparable to that of experimental methods. The optimal contact definitions constitute key guidelines for methods based on contact maps such as structure prediction through

  4. Systemic contact dermatitis

    Daria Nowak


    Full Text Available Systemic contact dermatitis (SCD is a skin inflammation occurring in a patient after systemic administration of a hapten, which previously caused an allergic contact skin reaction in the same person. Most frequently, hypersensitivity reactions typical for SCD occur after absorption of haptens with food or inhalation. Haptens occur mainly in the forms of metals and compounds present in natural resins, preservatives, food thickeners, flavorings and medicines. For many years, several studies have been conducted on understanding the pathogenesis of SCD in which both delayed type hypersensitivity (type IV and immediate type I are observed. Components of the complement system are also suspected to attend there. Helper T cells (Th (Th1 and Th2, cytotoxic T lymphocytes (Tc, and NK cells play a crucial role in the pathogenesis of SCD. They secrete a number of pro-inflammatory cytokines. In addition, regulatory T cells (Tregs have an important role. They control and inhibit activity of the immune system during inflammation. Tregs release suppressor cytokines and interact directly with a target cell through presentation of immunosuppressive particles at the cell surface. Diagnostic methods are generally the patch test, oral provocation test, elimination diet and lymphocyte stimulation test. There are many kinds of inflammatory skin reactions caused by systemic haptens’ distribution. They are manifested in a variety of clinical phenotypes of the disease.

  5. [Systemic contact dermatitis].

    Nowak, Daria; Gomułka, Krzysztof; Dziemieszonek, Paulina; Panaszek, Bernard


    Systemic contact dermatitis (SCD) is a skin inflammation occurring in a patient after systemic administration of a hapten, which previously caused an allergic contact skin reaction in the same person. Most frequently, hypersensitivity reactions typical for SCD occur after absorption of haptens with food or inhalation. Haptens occur mainly in the forms of metals and compounds present in natural resins, preservatives, food thickeners, flavorings and medicines. For many years, several studies have been conducted on understanding the pathogenesis of SCD in which both delayed type hypersensitivity (type IV) and immediate type I are observed. Components of the complement system are also suspected to attend there. Helper T cells (Th) (Th1 and Th2), cytotoxic T lymphocytes (Tc), and NK cells play a crucial role in the pathogenesis of SCD. They secrete a number of pro-inflammatory cytokines. In addition, regulatory T cells (Tregs) have an important role. They control and inhibit activity of the immune system during inflammation. Tregs release suppressor cytokines and interact directly with a target cell through presentation of immunosuppressive particles at the cell surface. Diagnostic methods are generally the patch test, oral provocation test, elimination diet and lymphocyte stimulation test. There are many kinds of inflammatory skin reactions caused by systemic haptens' distribution. They are manifested in a variety of clinical phenotypes of the disease.

  6. Systemic contact dermatitis

    Daria Nowak


    Full Text Available Systemic contact dermatitis (SCD is a skin inflammation occurring in a patient after systemic administration of a hapten, which previously caused an allergic contact skin reaction in the same person. Most frequently, hypersensitivity reactions typical for SCD occur after absorption of haptens with food or inhalation. Haptens occur mainly in the forms of metals and compounds present in natural resins, preservatives, food thickeners, flavorings and medicines. For many years, several studies have been conducted on understanding the pathogenesis of SCD in which both delayed type hypersensitivity (type IV and immediate type I are observed. Components of the complement system are also suspected to attend there. Helper T cells (Th (Th1 and Th2, cytotoxic T lymphocytes (Tc, and NK cells play a crucial role in the pathogenesis of SCD. They secrete a number of pro-inflammatory cytokines. In addition, regulatory T cells (Tregs have an important role. They control and inhibit activity of the immune system during inflammation. Tregs release suppressor cytokines and interact directly with a target cell through presentation of immunosuppressive particles at the cell surface. Diagnostic methods are generally the patch test, oral provocation test, elimination diet and lymphocyte stimulation test. There are many kinds of inflammatory skin reactions caused by systemic haptens’ distribution. They are manifested in a variety of clinical phenotypes of the disease.

  7. Dynamic contact angle analysis of silicone hydrogel contact lenses.

    Read, Michael Leonard; Morgan, Philip Bruce; Kelly, Jeremiah Michael; Maldonado-Codina, Carole


    Contact angle measurements are used to infer the clinical wetting characteristics of contact lenses. Such characterization has become more commonplace since the introduction of silicone hydrogel contact lens materials, which have been associated with reduced in vivo wetting due to the inclusion of siloxane-containing components. Using consistent methodology and a single investigator, advancing and receding contact angles were measured for 11 commercially available silicone hydrogel contact lens types with a dynamic captive bubble technique employing customized, fully automated image analysis. Advancing contact angles were found to range between 20° and 72° with the lenses falling into six statistically discrete groupings. Receding contact angles fell within a narrower range, between 17° and 22°, with the lenses segregated into three groups. The relationship between these laboratory measurements and the clinical performance of the lenses requires further investigation.

  8. Determination of melamine in sauce and bean-sauce with solid phase extraction and ion pair chromatography%固相萃取-离子对色谱法测定酱油与黄豆酱中的三聚氰胺

    支晓芳; 李晓敏; 戴新华; 弓爱君; 方向


    建立了固相萃取-离子对色谱法测定酱油与黄豆酱中的三聚氰胺.样品经甲醇提取,Waters MCX固相萃取柱净化.分析时用Inertsill ODS-SP C18色谱柱(5μm,4.6 x250mm)分离.水(缓冲液:0.01moL/L柠檬酸+0.01moL/L辛烷磺酸钠,pH=3.0):乙腈=92:8(V/V)溶液为流动相,流速1.0mL/min,在紫外波长240nm下检测.三聚氰胺在0.02~2.00mg/L的范围内,有良好的线性关系(r2=0.9999),方法栓出限为1.0mg/kg,加标回收率在83.5%~109.3%范围内,相对标准偏差小于5.0%.%A method was developed for the determination of melamine in sauce and bean-sauce with solid phase extraction and ion pair chromatography.Samples were extracted with methanol and purified by Waters MCX solid phase extraction column.Chromatographic analysis was performed on a Inertsill ODS-SP C18 column (5μm,4.6 ×250mm) with 0.01 mol/L + 0.01 mol/L citric acid buffer( pH = 3 ) -acetonitrile ( 92∶8 ) as mobile phase and detected at 240nm.The presented method showed good linear relationship ( r2 = 0.9999 ) for melamine in the range of 0.02~2.00mg/LThe detection limit was 1.0mg/kg,and the recoveries ranged from 83.5% to 109.3% with relative standard deviation less than 5.0%.The method is fast,accurate,simple for melamine analysis.

  9. CLAE-PI aplicada ao doseamento de vitaminas do complexo B em misturas: fundamentação e validação de método Ion-pair HPLC applied to the assay of the vitamin B group mixture: theorical bases and method validation

    Eliane Maria Donato


    Full Text Available Um método simples e rápido para determinação simultânea das vitaminas nicotinamida, tiamina, piridoxina, riboflavina e pantotenato de cálcio, em associação com minerais, foi desenvolvido por cromatografia líquida de alta eficiência, utilizando a técnica de pareamento iônico, coluna C-8 Perkin Elmer (150 x 4,6 mm DI, partícula 5 mm, poro 80 Å e detector de ultravioleta (210 e 270 nm. A fase móvel composta de água e metanol (894:106, contendo 10 mM de hexanossulfonato de sódio, 0,5% de ácido acético e 0,1% de trietilamina a pH 3,5 promoveu excelente separação das vitaminas. O método foi aplicado com sucesso à forma farmacêutica de comprimidos e drágeas, contendo também minerais. Linearidade, precisão, recuperação e especificidade foram satisfatórias. A taxa de recuperação do método foi de 98% a 102% e os desvios padrão relativos encontrados variaram entre 0,9 e 2,5%.A rapid and simple method for the simultaneous determination of nicotinamide, thiamine, pyridoxine, riboflavin and calcium pantothenate, associated with minerals was developed by high performance liquid chromatography. These vitamins were simultaneously assayed by reversed-phase ion-pair HPLC with C-8 column Perkin Elmer (150 x 4.6 mm, 5 mm, 80 Å and UV detection (210 and 270 nm. A mobile phase of water-methanol (894:106, 10 mM hexanesulfonate, 0,5% acetic acid and 0,1% triethylamine at pH 3.5 allowed the most satisfactory separation of these vitamins. The method was successfully applied to the determination of vitamins in tablets and coated tablets. Linearity, precision, recovery and specificity were always satisfactory. The average recoveries were from 98% to 102% and the relative standard deviations were between 0.9 to 2.5%.

  10. Equilibrium contact angle or the most-stable contact angle?

    Montes Ruiz-Cabello, F J; Rodríguez-Valverde, M A; Cabrerizo-Vílchez, M A


    It is well-established that the equilibrium contact angle in a thermodynamic framework is an "unattainable" contact angle. Instead, the most-stable contact angle obtained from mechanical stimuli of the system is indeed experimentally accessible. Monitoring the susceptibility of a sessile drop to a mechanical stimulus enables to identify the most stable drop configuration within the practical range of contact angle hysteresis. Two different stimuli may be used with sessile drops: mechanical vibration and tilting. The most stable drop against vibration should reveal the changeless contact angle but against the gravity force, it should reveal the highest resistance to slide down. After the corresponding mechanical stimulus, once the excited drop configuration is examined, the focus will be on the contact angle of the initial drop configuration. This methodology needs to map significantly the static drop configurations with different stable contact angles. The most-stable contact angle, together with the advancing and receding contact angles, completes the description of physically realizable configurations of a solid-liquid system. Since the most-stable contact angle is energetically significant, it may be used in the Wenzel, Cassie or Cassie-Baxter equations accordingly or for the surface energy evaluation.

  11. Contact and Non-contact Measurements of Grinding Pins

    Magdziak Marek


    Full Text Available The paper presents the results of contact and non-contact measurements of external profiles of selected grinding pins. The measurements were conducted in order to choose the appropriate measuring technique in the case of the considered measurement task. In the case of contact measurements the coordinate measuring machine ACCURA II was applied. The used coordinate measuring machine was equipped with the contact scanning probe VAST XT and the Calypso inspection software. Contact coordinate measurements were performed by using of different measurement strategies. The applied strategies included different scanning velocities and distances between measured points. Non-contact measurements were conducted by means of the tool presetter produced by the Mahr company. On the basis of gained results the guidelines concerning measurements of grinding pins were formulated. The measurements of analyzed grinding pins performed by means of the non-contact measuring system are characterized by higher reproducibility than the contact measurements. The low reproducibility of contact measurements may be connected with the inaccuracy of the selected coordinate measuring machine and the measuring probe, the measurement parameters and environmental conditions in the laboratory where the coordinate measuring machine is located. Moreover, the paper presents the possible application of results of conducted investigations. The results of non-contact measurements can be used in the simulation studies of grinding processes. The simulations may reduce the costs of machining processes.

  12. Reducing contact resistance in graphene devices through contact area patterning.

    Smith, Joshua T; Franklin, Aaron D; Farmer, Damon B; Dimitrakopoulos, Christos D


    Performance of graphene electronics is limited by contact resistance associated with the metal-graphene (M-G) interface, where unique transport challenges arise as carriers are injected from a 3D metal into a 2D-graphene sheet. In this work, enhanced carrier injection is experimentally achieved in graphene devices by forming cuts in the graphene within the contact regions. These cuts are oriented normal to the channel and facilitate bonding between the contact metal and carbon atoms at the graphene cut edges, reproducibly maximizing "edge-contacted" injection. Despite the reduction in M-G contact area caused by these cuts, we find that a 32% reduction in contact resistance results in Cu-contacted, two-terminal devices, while a 22% reduction is achieved for top-gated graphene transistors with Pd contacts as compared to conventionally fabricated devices. The crucial role of contact annealing to facilitate this improvement is also elucidated. This simple approach provides a reliable and reproducible means of lowering contact resistance in graphene devices to bolster performance. Importantly, this enhancement requires no additional processing steps.

  13. Contact angle and local wetting at contact line.

    Li, Ri; Shan, Yanguang


    This theoretical study was motivated by recent experiments and theoretical work that had suggested the dependence of the static contact angle on the local wetting at the triple-phase contact line. We revisit this topic because the static contact angle as a local wetting parameter is still not widely understood and clearly known. To further clarify the relationship of the static contact angle with wetting, two approaches are applied to derive a general equation for the static contact angle of a droplet on a composite surface composed of heterogeneous components. A global approach based on the free surface energy of a thermodynamic system containing the droplet and solid surface shows the static contact angle as a function of local surface chemistry and local wetting state at the contact line. A local approach, in which only local forces acting on the contact line are considered, results in the same equation. The fact that the local approach agrees with the global approach further demonstrates the static contact angle as a local wetting parameter. Additionally, the study also suggests that the wetting described by the Wenzel and Cassie equations is also the local wetting of the contact line rather than the global wetting of the droplet.

  14. Mechanical Contact Experiments and Simulations

    Nielsen, Chris Valentin; Martins, P; Zhang, W.


    Mechanical contact is studied under dynamic development by means of a combined numerical and experimental investigation. The experiments are designed to allow dynamical development of non-planar contact areas with significant expansion in all three directions as the load is increased. Different...... geometries and different materials are analyzed including contact between dissimilar materials. The numerical implementation is performed with a finite element computer program based on the irreducible flow formulation, and contact between deformable objects is modelled by applying the penalty method....... The overall investigation serves for testing and validating the numerical implementation of the mechanical contact, which is one of the main contributions to a system intended for 3D simulation of resistance welding. Correct modelling of contact between parts to be welded, as well as contact with electrodes...

  15. Point contacts in encapsulated graphene

    Handschin, Clevin [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Swiss Nanoscience Institute, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Fülöp, Bálint; Csonka, Szabolcs [Department of Physics, Budapest University of Technology and Economics and Condensed Matter Research Group of the Hungarian Academy of Sciences, Budafoki ut 8, 1111 Budapest (Hungary); Makk, Péter; Blanter, Sofya; Weiss, Markus; Schönenberger, Christian, E-mail: [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)


    We present a method to establish inner point contacts with dimensions as small as 100 nm on hexagonal boron nitride (hBN) encapsulated graphene heterostructures by pre-patterning the top-hBN in a separate step prior to dry-stacking. 2- and 4-terminal field effect measurements between different lead combinations are in qualitative agreement with an electrostatic model assuming point-like contacts. The measured contact resistances are 0.5–1.5 kΩ per contact, which is quite low for such small contacts. By applying a perpendicular magnetic field, an insulating behaviour in the quantum Hall regime was observed, as expected for inner contacts. The fabricated contacts are compatible with high mobility graphene structures and open up the field for the realization of several electron optical proposals.

  16. Hair dye contact allergy

    Søsted, Heidi; Rastogi, Suresh Chandra; Andersen, Klaus Ejner


    Colouring of hair can cause severe allergic contact dermatitis. The most frequently reported hair dye allergens are p-phenylenediamine (PPD) and toluene-2,5-diamine, which are included in, respectively, the patch test standard series and the hairdressers series. The aim of the present study...... was to identify dye precursors and couplers in hair dyeing products causing clinical hair dye dermatitis and to compare the data with the contents of these compounds in a randomly selected set of similar products. The patient material comprised 9 cases of characteristic clinical allergic hair dye reaction, where...... exposure history and patch testing had identified a specific hair dye product as the cause of the reaction. The 9 products used by the patients were subjected to chemical analysis. 8 hair dye products contained toluene-2,5-diamine (0.18 to 0.98%). PPD (0.27%) was found in 1 product, and m-aminophenol (0...

  17. Contact dermatitis to Alstroemeria.

    Santucci, B; Picardo, M; Iavarone, C; Trogolo, C


    A study was carried out on 50 workers in a floriculture centre to evaluate the incidence of contact dermatitis to Alstroemeria. 3 subjects gave positive reactions to aqueous and ethanolic extracts of cut flowers, stems and leaves. By column chromatography, the allergen was isolated and its chemical structure identified as 6-tuliposide A by proton magnetic resonance and carbon-13 magnetic resonance. Only 6-tuliposide A was isolated from cut flowers, and this gave positive reactions when patch tested at 0.01%; a-methylene-gamma-butyrolactone at 10(-5) (v/v) was positive in the same 3 subjects. Other lactones (gamma-methylene-gamma-butyrolactone, alantolactone, isoalantolactone) were negative at all concentrations used.

  18. Fragrance contact allergy

    Johansen, Jeanne D


    in the same products. This means that it is difficult to avoid exposure, as products labelled as 'fragrance free' have also been shown to contain fragrance ingredients, either because of the use of fragrance ingredients as preservatives or masking perfumes, or the use of botanicals. About 2500 different...... typically have a history of rash to a fine fragrance or scented deodorants. Chemical analysis has revealed that well known allergens from the fragrance mix are present in 15-100% of cosmetic products, including deodorants and fine fragrances, and most often in combinations of three to four allergens...... fragrance ingredients are currently used in the composition of perfumes and at least 100 of these are known contact allergens. Therefore, it is advisable to supplement standard patch testing with the patient's own stay-on cosmetic products, as well as the fragrance chemical hydroxyisohexyl-3-cyclohexane...

  19. Fragrance contact allergy

    Johansen, Jeanne D


    typically have a history of rash to a fine fragrance or scented deodorants. Chemical analysis has revealed that well known allergens from the fragrance mix are present in 15-100% of cosmetic products, including deodorants and fine fragrances, and most often in combinations of three to four allergens...... in the same products. This means that it is difficult to avoid exposure, as products labelled as 'fragrance free' have also been shown to contain fragrance ingredients, either because of the use of fragrance ingredients as preservatives or masking perfumes, or the use of botanicals. About 2500 different...... fragrance ingredients are currently used in the composition of perfumes and at least 100 of these are known contact allergens. Therefore, it is advisable to supplement standard patch testing with the patient's own stay-on cosmetic products, as well as the fragrance chemical hydroxyisohexyl-3-cyclohexane...

  20. Cosmetic Contact Allergens

    An Goossens


    Full Text Available This article presents trends in the frequency of cosmetics as causal factors of allergic contact dermatitis during a 26-year period in 14,911 patients patch-tested between 1990 and 2014, and discusses the cosmetic allergens identified during the last six years (2010–2015 in 603 patients out of 3105 tested. The data were retrieved from, and evaluated with, a patient database developed in-house. The results show the increasing importance of cosmetic allergies, up to 25% of the patients tested during the last five-year period. As expected, fragrance materials, preservatives, and hair dyes were the most frequent culprits, but a great variety of other allergenic ingredients were involved as well. This underlines the need of additional and extensive patch testing with the patient’s products used and their ingredients.

  1. Mechanoluminescent Contact Type Sensor

    A. K. Yefremov


    Full Text Available Mechanoluminescent sensing elements convert mechanical stress into optical radiation. Advantages of such sensors are the ability to generate an optical signal, solid-state, simple structure, and resistance to electromagnetic interference. Mechanoluminescent sensor implementations can possess the concentrated and distributed sensitivity, thereby allowing us to detect the field of mechanical stresses distributed across the area and in volume. Most modern semiconductor photo-detectors can detect mechanoluminescent radiation, so there are no difficulties to provide its detection when designing the mechanoluminescent sensing devices. Mechanoluminescent substances have especial sensitivity to shock loads, and this effect can be used to create a fuse the structure of which includes a target contact type sensor with a photosensitive actuator. The paper briefly describes the theoretical basics of mechanoluminiscence: a light signal emerges from the interaction of crystalline phosphor luminescence centers with electrically charged dislocations, moving due to the deformation of the crystal. A mathematical model of the mechanoluminescent conversion is represented as a functional interaction between parameters of the mechanical shock excitation and the sensor light emission. Examples of computing the optical mechanoluminescent output signal depending on the duration and peak level of impulse load are given. It is shown that the luminous flux, generated by mechanoluminescent sensing element when there is an ammunition-target collision causes the current emerging in photo-detector (photodiode that is sufficient for a typical actuator of the fuse train to operate. The potential possibility to create a contact target type sensor based on the light-sensitive mechanoluminescent sensor was proved by the calculation and simulation results.

  2. Kinetics of uncatalyzed thermochemical sulfate reduction by sulfur-free paraffin

    Zhang, Tongwei; Ellis, Geoffrey S.; Ma, Qisheng; Amrani, Alon; Tang, Yongchun


    published experimental TSR data yield kinetic parameters that are consistent with our values. Assuming MgSO4 contact-ion-pair ([MgSO4]CIP) as the reactive form of sulfate in petroleum reservoir formation waters, a simple extrapolation of our experimentally derived HSO4− reduction kinetics as a proxy for [MgSO4]CIP to geologically reasonable conditions predicts onset temperatures (130–140 °C) that are comparable to those observed in nature.


    Wang Fujun; Cheng Jiangang; Yao Zhenhan


    A new contact searching algorithm for contact-impact systems is proposed in this paper. In terms of the cell structure and the linked-list, this algorithm solves the problem of sorting and searching contacts in three dimensions by transforming it to a retrieving process from two one-dimensional arrays, and binary searching is no longer required. Using this algorithm, the cost of contact searching is reduced to the order of O(N) instead of O(Nlog2N) for traditional ones, where N is the node number in the system. Moreover, this algorithm can handle contact systems with arbitrary mesh layouts. Due to the simplicity of this algorithm it can be easily implemented in a dynamic explicit finite element Program. Our numerical experimental result shows that this algorithm is reliable and efficient for contact searching of three dimensional systems.

  4. Robust Algorithms for Contact Problems with Constitutive Contact Laws


    This thesis is concerned with the solution of contact problems with advanced Coulomb friction in the 3D case using the finite element method. A Lagrange multiplier method modelling the contact traction is employed and the contact conditions are enforced in a weak sense leading to a surface-to-surface discretization. Here more precisely the dual mortar method is used allowing for a static condensation of the additional variables in the system before solving without loosing the optimality of...

  5. Hysteresis during contact angles measurement.

    Diaz, M Elena; Fuentes, Javier; Cerro, Ramon L; Savage, Michael D


    A theory, based on the presence of an adsorbed film in the vicinity of the triple contact line, provides a molecular interpretation of intrinsic hysteresis during the measurement of static contact angles. Static contact angles are measured by placing a sessile drop on top of a flat solid surface. If the solid surface has not been previously in contact with a vapor phase saturated with the molecules of the liquid phase, the solid surface is free of adsorbed liquid molecules. In the absence of an adsorbed film, molecular forces configure an advancing contact angle larger than the static contact angle. After some time, due to an evaporation/adsorption process, the interface of the drop coexists with an adsorbed film of liquid molecules as part of the equilibrium configuration, denoted as the static contact angle. This equilibrium configuration is metastable because the droplet has a larger vapor pressure than the surrounding flat film. As the drop evaporates, the vapor/liquid interface contracts and the apparent contact line moves towards the center of the drop. During this process, the film left behind is thicker than the adsorbed film and molecular attraction results in a receding contact angle, smaller than the equilibrium contact angle.

  6. Determination of the activity of nucleoside diphosphate kinase in human red blood cell by reversed phase ion-pair HPLC%离子对高效液相色谱法测定人体红细胞内核苷二磷酸激酶活性

    沈如飞; 刘亚妮; 曾繁典; 师少军


    OBJECTIVE To establish a reversed phase ion-pair HPLC method for the determination of the activity of nucleo-side diphosphate kinase (NDPK) in human red blood cells (RBC). METHODS RBC with reaction substrates (dADP and dGTP) and other reaction mixtures were incubated at 37 ℃ for 5 min.then inactivated by heating at 100 °C for 10 min.and cen-trituged with supernatant sample for analysis. dATP concentrations were quantified for the determination of the activity of NDPK in human RBC. Separation was achieved by SymmetryShield TM RP18(150 mm×3. 9 mm, 5 μm) with UV detection at 260 nm and column temperature of 25 t. Using gradient elution,the mobile phase A consisted of mixture of 20 tnmol·'L-1 KH2PO4--K2HPO4buffer solution and ion-pairing reagent 5 mmol·L-1TBAHS,and mobile phase B was acetonitrile. RESULTS NDPK could catalyze ADP + dGTP←→dATP + dGDP reaction specifically. The calibration curve was linear over the range of 4. 33 -43. 34 μmol·L-1 (r2 - 1.000) and the limit of quantitation was 4. 33 μmol·L-1. The intra- and inter-assay coefficients of variation were less than 5. 53% and 6. 69% , respectively. The mean analytical recoveries of dATP were 98. 4% - 104. 2% and the mean absolute recoveries were all more than 83%. A stability study showed that dATP samples in RBC were stable at room temperature or at 4 t for at least 24 hours,as well as for at least 30 days at - 80 ℃ after three freeze-thaw cycles. CONCLUSION This method is -simple,rapid,sensitive,specific,and can be applied to study the relationship between activity of NDPK and efficacy and toxicity of thiopurines.%目的:建立测定人体红细胞(RBC)内核苷二磷酸激酶( NDPK)活性的反相离子对高效液相色谱法.方法:稀释RBC中加入反应底物(dADP和dGTP)及其他反应混合液后,37℃孵育5 min,100℃灭活10 min,离心取上清液进样分析.以反应产物dATP定量分析NDPK活性.色谱柱为SymmetryShield TM RP18(150 mm×3.9mm,5μm),检测波长为260 nm

  7. "Hot cores" in proteins: Comparative analysis of the apolar contact area in structures from hyper/thermophilic and mesophilic organisms

    Bossa Francesco


    Full Text Available Abstract Background A wide variety of stabilizing factors have been invoked so far to elucidate the structural basis of protein thermostability. These include, amongst the others, a higher number of ion-pairs interactions and hydrogen bonds, together with a better packing of hydrophobic residues. It has been frequently observed that packing of hydrophobic side chains is improved in hyperthermophilic proteins, when compared to their mesophilic counterparts. In this work, protein crystal structures from hyper/thermophilic organisms and their mesophilic homologs have been compared, in order to quantify the difference of apolar contact area and to assess the role played by the hydrophobic contacts in the stabilization of the protein core, at high temperatures. Results The construction of two datasets was carried out so as to satisfy several restrictive criteria, such as minimum redundancy, resolution and R-value thresholds and lack of any structural defect in the collected structures. This approach allowed to quantify with relatively high precision the apolar contact area between interacting residues, reducing the uncertainty due to the position of atoms in the crystal structures, the redundancy of data and the size of the dataset. To identify the common core regions of these proteins, the study was focused on segments that conserve a similar main chain conformation in the structures analyzed, excluding the intervening regions whose structure differs markedly. The results indicated that hyperthermophilic proteins underwent a significant increase of the hydrophobic contact area contributed by those residues composing the alpha-helices of the structurally conserved regions. Conclusion This study indicates the decreased flexibility of alpha-helices in proteins core as a major factor contributing to the enhanced termostability of a number of hyperthermophilic proteins. This effect, in turn, may be due to an increased number of buried methyl groups in

  8. Contact sport and osteoarthritis.

    Molloy, Michael G


    Osteoarthritis (OA) is the most common joint disease in the world and the single largest cause of disability for those over 18 years. It affects more than twice as many people as does cardiac disease, and increases in incidence and prevalence with age. Animal and human studies have shown no evidence of increased risk of hip or knee OA with moderate exercise and in the absence of traumatic injury, sporting activity has a protective effect. One age-matched case control study found recreational runners who ran 12-14 miles per week for up to 40 years had no increase in radiological or symptomatic hip or knee OA. However, higher rates of hip OA occur in contact sports than in age-matched controls, with the highest rate in professional players. Soccer players with torn anterior cruciate ligaments (ACL) are more likely to develop knee OA than those with intact ACL. Early ACL repair reduces the risk of knee OA, but does not prevent it. Established injury prevention programmes have been refined to prevent injuries such as ACL rupture.

  9. Noise of sliding rough contact

    Le Bot, Alain


    This article is a discussion about the origin of friction noise produced when rubbing solids having rough surfaces. We show that noise emerges from numerous impacts into the contact between antagonist asperities of surfaces. Prediction of sound sources reduces to a statistical problem of contact mechanics. On the other hand, contact is also responsible of dissipation of vibration. This leads to the paradoxical result that the noise may not be proportional to the number of sources.

  10. Ion Implanted Passivated Contacts for Interdigitated Back Contacted Solar Cells

    Young, David L.; Nemeth, William; LaSalvia, Vincenzo; Reedy, Robert; Bateman, Nicholas; Stradins, Pauls


    We describe work towards an interdigitated back contacted (IBC) solar cell utilizing ion implanted, passivated contacts. Formation of electron and hole passivated contacts to n-type CZ wafers using tunneling SiO2 and ion implanted amorphous silicon (a-Si) are described. P and B were ion implanted into intrinsic amorphous Si films at several doses and energies. A series of post-implant anneals showed that the passivation quality improved with increasing annealing temperatures up to 900 degrees C. The recombination parameter, Jo, as measured by a Sinton lifetime tester, was Jo ~ 14 fA/cm2 for Si:P, and Jo ~ 56 fA/cm2 for Si:B contacts. The contact resistivity for the passivated contacts, as measured by TLM patterns, was 14 milliohm-cm2 for the n-type contact and 0.6 milliohm-cm2 for the p-type contact. These Jo and pcontact values are encouraging for forming IBC cells using ion implantation to spatially define dopants.

  11. Contextualizing Intergroup Contact: Do Political Party Cues Enhance Contact Effects?

    Sønderskov, Kim Mannemar; Thomsen, Jens Peter Frølund


    This article examines intergroup contact effects in different political contexts. We expand on previous efforts of social psychologists by incorporating the messages of political parties as a contextual trigger of group membership awareness in contact situations. We argue that the focus among...

  12. CISM Course on Rolling Contact Phenomena

    Kalker, Joost


    Preface.- Rolling Contact Phenomena - Linear Elasticity.- Finite Element Methods for Rolling Contact.- Plastic Deformation in Rolling Contact.- Non-Steady State Rolling Contact and Corrugations.- Modelling of Tyre Force and Moment Generation.- Rolling Noise.- Lubrication

  13. Contact line and contact angle dynamics in superhydrophobic channels.

    Zhang, Junfeng; Kwok, Daniel Y


    The dynamics of the wetting and movement of a three-phase contact line confined between two superhydrophobic surfaces were studied using a mean-field free-energy lattice Boltzmann model. Principle features of superhydrophobic surfaces, such as trapped vapor/air between rough microstructures, high contact angles, reduced contact angle hysteresis, and low resistance to fluid flow, were all observed. Movement of the three-phase contact line over a well-patterned superhydrophobic surface displays a periodic stick-jump-slip behavior, while the dynamic contact angle changes accordingly from maximum to minimum. Two regimes were found for the flow velocity as a function of surface roughness and can be related directly to the balance between driving force and flow resistance. This work provides a better understanding of dynamic wetting and fluid flow behaviors over superhydrophobic surfaces and hence could be useful in related applications.

  14. Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

    Yang, Chunyan; Persson, Bo


    We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load [1-4]. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the interfacial separation approaches to zero. The present results may be very important for soft solids, e.g., rubber, or for very smooth surfaces, where complete contact can be reached at moderate high loads without plastic deformation of the solids. References: [1] C. Yang and B.N.J. Persson, arXiv:0710.0276, (to appear in Phys. Rev. Lett.) [2] B.N.J. Persson, Phys. Rev. Lett. 99, 125502 (2007) [3] L. Pei, S. Hyun, J.F. Molinari and M.O. Robbins, J. Mech. Phys. Sol. 53, 2385 (2005) [4] M. Benz, K.J. Rosenberg, E.J. Kramer and J.N. Israelachvili, J. Phy. Chem. B.110, 11884 (2006)

  15. 整体柱离子对色谱-紫外检测法快速测定对甲苯磺酸根%Rapid determination of p-toluenesulfonate using monolithic column ion-pair chromatography coupled with ultraviolet detection

    李红杏; 于泓; 张于


    In this article,ion-pair chromatography with ultraviolet detection was used in the analysis of p-toluenesulfonate. The ana-lyte was separated using a mobile phase of tetrabutylammonium hydroxide( TBA)-citric acid-acetonitrile on a reversed-phase silica-based monolithic column. The ultraviolet detection wavelength,the composition of mobile phase,column temperature and flow rate on the ion retention and separation were investigated,retention rule was discussed. The chromatographic conditions were optimized:at 230 nm wavelength,when 0. 4 mmol·L-1 TBA-0. 13 mmol·L-1 citric acid-15%(v/v)acetonitrile(pH 5. 5)was used as mobile phase with column temperature of 40℃ and flow rate of 3. 0 mL·min-1 ,retention time of C7 H7 SO3-was less than 1. 25 min. Common inor-ganic anions( Cl-,NO3-) did not interfere with the determination. In the range of 0. 7-100 mg·L-1 ,the correlation coefficient of line-ar regression equation was 0. 9997. Relative standard deviation(RSD)of chromatographic peak area was 1. 0%(n=5). Detection limit(S/N=3)was 0. 2 mg·L-1. The method has been applied to the determination of p-toluenesulfonate ionic liquid samples syn-thesized by chemistry laboratory. Standard addition recovery rate was 101%. The method was simple and rapid.%研究了整体柱离子对色谱结合紫外检测的方法分析对甲苯磺酸根( C7 H7 SO3-)。采用反相硅胶整体柱,以氢氧化四丁基铵-柠檬酸-乙腈为流动相,考察了紫外检测波长、流动相组成、色谱柱温度和流速对离子保留的影响。色谱条件经过优化,在紫外检测波长230 nm,流动相为0.4 mmol·L-1氢氧化四丁基胺( TBA)-0.13 mmol·L-1柠檬酸-15%(v/v)乙腈(pH 5.5),流速3.0 mL·min-1,柱温40℃的条件下,C7H7SO3-的保留时间为1.25 min内。常见无机阴离子( Cl-,NO3-)不干扰测定。在0.7~100 mg·L-1范围内,线性回归方程的相关系数为0.9997,峰面积的相对标准偏差(RSD,n=5)为1.0%,检出限(S/N=3)为0.2 mg·L-1

  16. Metodologia para determinação de digluconato de clorhexidina em carcaças de frango utilizando CLAE - par iônico e avaliação de resíduos durante a refrigeração e congelamento HPLC - ion pairing determination of chlorhexidine digluconate in treated poultry carcasses. Analysis during refrigeration and freezing

    Eduardo Vicente


    Full Text Available O uso do digluconato de clorhexidina (DGCH na higienização de equipamentos e instalações na indústria de alimentos e o interesse de aplicação deste produto como sanitizante em carcaças de frango indicam a necessidade da avaliação de resíduos no alimento. Um método por cromatografia líquida de alta eficiência (CLAE com pareamento de íons, incluindo extração com éter etílico em meio alcalino, foi desenvolvido para determinação de clorhexidina em carne de frango. O limite de quantificação do método (0,6mg/g e a recuperação média em carcaça (75% - CV 10%, em pele (72% - CV 7% e na musculatura (82% - CV 8% foram considerados adequados aos propósitos do método. As análises de carcaças e pele tratadas, mantidas refrigeradas ou congeladas, permitiu constatar que ocorreu uma pequena redução nos níveis residuais de DGCH durante o período de armazenamento. Como prováveis causas desta diminuição devem ser considerados a interação com componentes polares da matriz, a perda juntamente com os fluidos liberados dos tecidos durante o armazenamento refrigerado ou no descongelamento de carcaças inteiras e a degradação da clorhexidina. A ausência deste sanitizante na musculatura após o armazenamento refrigerado indica que nas condições empregadas, o DGCH não atravessa a barreira da pele.The use of the antimicrobial agent chlorhexidine digluconate in the sanitization of food industry equipment and installations, and the interest on its application to decontaminate poultry carcasses indicates the need to determine its residue in food. An ion pairing HPLC - UV analytical method including an ethyl ether extraction in alkaline medium was developed to measure clorhexidine residue in poultry meat. The limit of analytical quantitation (0,6mg/g and recoveries in carcasses (75% - CV 10%, skin (72% - CV 7%, and muscular tissue (82% - CV 8% were appropriate to the purposes of the method application. The analysis of treated

  17. Determination of Content of Four Components for Trabit Injection A by Reverse-Phase Ion Pair HPLC%反相离子对高效液相色谱法测定泰必治注射液A中4种组分的含量

    韩澄华; 聂小春


    目的:采用反相离子对高效液相色谱法测定泰必治注射液A中盐酸利多卡因、地塞米松、卡巴芬乙酸(钠盐)与保泰松钠4种组分的含量。方法:采用YWG-C18(10 μm,4.5 mm×150 mm)色谱柱,以乙腈-水(45∶55,含2.5 mmol.L-1十六烷基三甲基溴化铵)为流动相,流速1.5 mL.min-1,柱温40 ℃,检测波长230 nm。结果:本法可同时测定4种组分的含量。盐酸利多卡因在13~64 μg.mL-1、地塞米松在4.5~38 μg.mL-1、卡巴芬乙酸(钠盐)在269~1 614 μg.mL-1、保泰松钠在402~2 077 μg.mL-1范围内,峰面积与其浓度呈良好的线性关系;平均回收率(n=5)依次为99.9%(RSD=1.2%),101.0%(RSD=0.4%),100.5%(RSD=0.2%),100.6%(RSD=0.8%)。结论:方法简便、快速、准确,可作为样品的检测方法。%Objective:To establish a method using reverse-phase ion pair HPLC,for determining the content of four components—lidocaine hydrochloride,dexamethasone,o-carbamoylphenoxyacetic acid(sodium salt),phenylbutazone sodium of trabit injection A.Method:Used a YWG-C18(4.5 mm×150 mm,10 μm)column,the mobile phase consisted of 2.5 mmol*mL-1 cetyltrimethylammonium bromide-acetonitrile(55∶45),at a flow rate of 1.5 mL*min-1.The column temperature was 40 ℃ and UV detection wavelength was 230 nm.Results:The contents of four components can be simultaneously determined.The calibration curves were linear in the range of 13~64 μg*mL-1 for lidocaine hydrochloride,4.5~38 μg*mL-1 for dexamethason,269~1 614 μg*mL-1 for o-carbamoylphenoxyacetic acid(sodium salt),402~2 077 μg*mL-1 for phenylbutazone sodium respectively.The average recoveries of the four components above respectively were 99.9%(RSD=1.2%),101.0%(RSD=0.4%),100.5%(RSD=0.2%),100.6%(RSD=0.8%).Conclusion:This method is simple,fast and accurate.

  18. Mechanical Contact Experiments and Simulations

    Nielsen, Chris Valentin; Martins, P; Zhang, W.;


    Mechanical contact is studied under dynamic development by means of a combined numerical and experimental investigation. The experiments are designed to allow dynamical development of non-planar contact areas with significant expansion in all three directions as the load is increased. Different...

  19. Contact modeling for robotics applications

    Lafarge, R.A.; Lewis, C.


    At Sandia National Laboratories (SNL), the authors are developing the ability to accurately predict motions for arbitrary numbers of bodies of arbitrary shapes experiencing multiple applied forces and intermittent contacts. In particular, the authors are concerned with the simulation of systems such as part feeders or mobile robots operating in realistic environments. Preliminary investigation of commercial dynamics software packages led them to the conclusion that they could use commercial software to provide everything they needed except for the contact model. They found that ADAMS best fit their needs for a simulation package. To simulate intermittent contacts, they need collision detection software that can efficiently compute the distances between non-convex objects and return the associated witness features. They also require a computationally efficient contact model for rapid simulation of impact, sustained contact under load, and transition to and from contact conditions. This paper provides a technical review of a custom hierarchical distance computation engine developed at Sandia, called the C-Space Toolkit (CSTk). In addition, they describe an efficient contact model using a non-linear damping term developed by SNL and Ohio State. Both the CSTk and the non-linear damper have been incorporated in a simplified two-body testbed code, which is used to investigate how to correctly model the contact using these two utilities. They have incorporated this model into the ADAMS software using the callable function interface. An example that illustrates the capabilities of the 9.02 release of ADAMS with their extensions is provided.

  20. The importance of contact quality

    van Bakel, Marian; Gerritsen, Marinel; van Oudenhoven, Jan Pieter

    Establishing contact between expatriates and a local host has been found to reap benefits with regard to Interaction Adjustment, Host National Social Support, Open-mindedness, and Social Initiative. This longitudinal study examines the role of the quality of contact for these four aspects. Expatr...

  1. Drops, contact lines, and electrowetting

    Mannetje, 't D.J.C.M.


    In this work, we study the behaviour of drops and contact lines under the influence of electric fields, and how these can answer fundamental and industrial questions. Our focus is on studying the varying balance of the electric field, hysteresis forces and inertia as the speed of a contact line chan

  2. Body contact and body language

    Winther, Helle Dagmar


    Body contact and body language are unique and existential and, although culturally dependent and socially embodied, they are also universal communication forms. For small children all over the world, warm, close and nourishing body contact is fundamental to their embodied experi­ence of themselve...

  3. Fabricating customized hydrogel contact lens

    Childs, Andre; Li, Hao; Lewittes, Daniella M.; Dong, Biqin; Liu, Wenzhong; Shu, Xiao; Sun, Cheng; Zhang, Hao F.


    Contact lenses are increasingly used in laboratories for in vivo animal retinal imaging and pre-clinical studies. The lens shapes often need modification to optimally fit corneas of individual test subjects. However, the choices from commercially available contact lenses are rather limited. Here, we report a flexible method to fabricate customized hydrogel contact lenses. We showed that the fabricated hydrogel is highly transparent, with refractive indices ranging from 1.42 to 1.45 in the spectra range from 400 nm to 800 nm. The Young’s modulus (1.47 MPa) and hydrophobicity (with a sessile drop contact angle of 40.5°) have also been characterized experimentally. Retinal imaging using optical coherence tomography in rats wearing our customized contact lenses has the quality comparable to the control case without the contact lens. Our method could significantly reduce the cost and the lead time for fabricating soft contact lenses with customized shapes, and benefit the laboratorial-used contact lenses in pre-clinical studies.

  4. Emotional Satisfaction of Customer Contacts

    Güngör, Hüseyin


    For marketing and customer services researchers and professionals who are interested in customer contacts, customer satisfaction and loyalty issues. Contact centers are playing a pivotal role in customer services of the 21st century. Nevertheless, despite their growing importance and presence, conta

  5. Emotional Satisfaction of Customer Contacts

    Güngör, Hüseyin


    For marketing and customer services researchers and professionals who are interested in customer contacts, customer satisfaction and loyalty issues. Contact centers are playing a pivotal role in customer services of the 21st century. Nevertheless, despite their growing importance and presence,

  6. Emotional Satisfaction of Customer Contacts

    Güngör, Hüseyin


    For marketing and customer services researchers and professionals who are interested in customer contacts, customer satisfaction and loyalty issues. Contact centers are playing a pivotal role in customer services of the 21st century. Nevertheless, despite their growing importance and presence, conta

  7. Aluminum break-point contacts

    Heinemann, Martina; Groot, R.A. de


    Ab initio molecular dynamics is used to study the contribution of a single Al atom to an aluminum breakpoint contact during the final stages of breaking and the initial stages of the formation of such a contact. A hysteresis effect is found in excellent agreement with experiment and the form of the

  8. Contact dermatitis in military personnel.

    Dever, Tara T; Walters, Michelle; Jacob, Sharon


    Military personnel encounter the same allergens and irritants as their civilian counterparts and are just as likely to develop contact dermatitis from common exposures encountered in everyday life. In addition, they face some unique exposures that can be difficult to avoid owing to their occupational duties. Contact dermatitis can be detrimental to a military member's career if he or she is unable to perform core duties or avoid the inciting substances. An uncontrolled contact dermatitis can result in the member's being placed on limited-duty (ie, nondeployable) status, needing a job or rate change, or separation from military service. We present some common causes of contact dermatitis in military personnel worldwide and some novel sources of contact dermatitis in this population that may not be intuitive.

  9. Multifocal contact lens myopia control.

    Walline, Jeffrey J; Greiner, Katie L; McVey, M Elizabeth; Jones-Jordan, Lisa A


    Previous studies on soft multifocal contact lens myopia control published in the peer-reviewed literature reported findings of noncommercial contact lenses worn for 1 year or less. This study sought to determine the progression of myopia and axial elongation of children fitted with commercially available distance center soft multifocal contact lenses for 2 years. Eight- to eleven-year-old children with -1.00 D to -6.00 D spherical component and less than 1.00 D astigmatism were fitted with soft multifocal contact lenses with a +2.00 D add (Proclear Multifocal "D"; CooperVision, Fairport, NY). They were age- and gender-matched to participants from a previous study who were fitted with single-vision contact lenses (1 Day Acuvue; Vistakon, Jacksonville, FL). A-scan ultrasound and cycloplegic autorefraction were performed at baseline, after 1 year, and after 2 years. Multilevel modeling was used to compare the rate of change of myopia and axial length between single-vision and soft multifocal contact lens wearers. Forty participants were fitted with soft multifocal contact lenses, and 13 did not contribute complete data (5 contributed 1 year of data). The adjusted mean ± standard error spherical equivalent progression of myopia at 2 years was -1.03 ± 0.06 D for the single-vision contact lens wearers and -0.51 ± 0.06 for the soft multifocal contact lens wearers (p < 0.0001). The adjusted mean axial elongation was 0.41 ± 0.03 and 0.29 ± 0.03 for the single-vision and soft multifocal contact lens wearers, respectively (p < 0.0016). Soft multifocal contact lens wear resulted in a 50% reduction in the progression of myopia and a 29% reduction in axial elongation during the 2-year treatment period compared to a historical control group. Results from this and other investigations indicate a need for a long-term randomized clinical trial to investigate the potential for soft multifocal contact lens myopia control.

  10. Contact allergy to epoxy resin

    Bangsgaard, Nannie; Thyssen, Jacob Pontoppidan; Menné, Torkil


    . Objectives. To evaluate the prevalence of contact allergy to epoxy resin monomer (diglycidyl ether of bisphenol A; MW 340) among patients with suspected contact dermatitis and relate this to occupation and work-related consequences. Patients/methods. The dataset comprised 20 808 consecutive dermatitis...... in an educational programme. Conclusion. The 1% prevalence of epoxy resin contact allergy is equivalent to reports from other countries. The high occurrence of epoxy resin exposure at work, and the limited use of protective measures, indicate that reinforcement of the law is required....

  11. All-graphene edge contacts

    Jacobsen, Kåre Wedel; Falkenberg, Jesper Toft; Papior, Nick Rübner;


    Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures...... to be in therange of 1-10 kΩμm which is comparable to the best contact resistance reportedfor edge-contacted graphene-metal contacts. We conclude that conductingall-carbon T-junctions should be feasible....

  12. Medical management of contact dermatitis.

    Alexandroff, A B; Johnston, G A


    Allergic and irritant contact dermatitis are important dermatological problems. Although the frequencies of positive reactions to a number of allergens have decreased during last 30 years because of better avoidance (and at least in part due to improved legislation), contact allergy to other agents is rising. The medical treatment starts from a correct identification of triggers of contact dermatitis which could allow patients to reduce or avoid exposure to these agents in future. A good clinical history, examination and immunological tests including patch testing are of crucial importance at this stage. Further management includes emollients, topical and oral corticosteroids, topical calcineurin inhibitors, azathioprine and ciclosporin. Methotrexate and alitretinoin are recent additions to the armamentarium of dermatologists who manage contact dermatitis.

  13. Scalable algorithms for contact problems

    Dostál, Zdeněk; Sadowská, Marie; Vondrák, Vít


    This book presents a comprehensive and self-contained treatment of the authors’ newly developed scalable algorithms for the solutions of multibody contact problems of linear elasticity. The brand new feature of these algorithms is theoretically supported numerical scalability and parallel scalability demonstrated on problems discretized by billions of degrees of freedom. The theory supports solving multibody frictionless contact problems, contact problems with possibly orthotropic Tresca’s friction, and transient contact problems. It covers BEM discretization, jumping coefficients, floating bodies, mortar non-penetration conditions, etc. The exposition is divided into four parts, the first of which reviews appropriate facets of linear algebra, optimization, and analysis. The most important algorithms and optimality results are presented in the third part of the volume. The presentation is complete, including continuous formulation, discretization, decomposition, optimality results, and numerical experimen...

  14. Occupational contact dermatitis in hairdressers

    Schwensen, Jakob F; Johansen, Jeanne Duus; Veien, Niels K


    BACKGROUND: Occupational contact dermatitis among hairdressers is frequent, owing to daily exposure to irritants and allergens. OBJECTIVES: To identify sensitization to the most common allergens associated with the occupation of hairdressing. METHODS: Patch test results of 399 hairdressers and 19...

  15. Dendritic cells and contact dermatitis.

    Sasaki, Yoshinori; Aiba, Setsuya


    Contact dermatitis is a biological response to simple chemicals in the skin. Although it is well known that allergic contact dermatitis is mediated by the immune system, it is still uncertain whether it is a kind of protective response or it is simply an unnecessary response. We have demonstrated the following: (1) haptens activate Langerhans cells in the initiation phase of murine allergic contact dermatitis in vivo, (2) haptens activate human monocyte-derived dendritic cells in vitro, (3) the activation of dendritic cells by haptens is primarily mediated by the activation of p38 mitogen-activated protein kinase (MAPK), and (4) the activation of p38 MAPK is mediated by stimulation related to an imbalance of intracellular redox. Based on these observations, we will discuss the biological significance of contact dermatitis. In addition, we will review some up-to-date findings on Langerhans cell biology.

  16. Contact vitiligo: etiology and treatment

    Singh P


    Full Text Available Fifty patients of contact vitiligo were studied. EtiologicaI agents of contact vitiligo were identified by clinical history, distribution of lesions and patch testing with suspected material. All patients were advised to avoid the suspected agent and treated with PUVASOL and topical steroid. Out of 50 patients (Male 8%, Female 92% age 14-60 years., etiological agent of contact vitiligo was found to be sticking bindi alone in 24 (48%, while bindi along with other etiological agents were found to be purse, foot wear, plastic watch strap, lipstick and tooth paste in 14 ( 28% cases. 14 (28% patients also had disseminated lesions of vitiligo along with contact vitiligo. Positive reaction with patch testing was observed in 18 (36% while depigmentation was seen in 4 ( 8% cases. We observed that response of treatment was better in patients with shorter duration of disease while poor response was seen in patients with longer duration of disease.

  17. The geometry of surfaces contact

    Siegl J.


    Full Text Available This contribution deals with a geometrical exact description of contact between two given surfaces which are defined by the vector functions. These surfaces are substituted at a contact point by approximate surfaces of the second order in accordance with the Taylor series and consequently there is derived a differential surface of these second order surfaces. Knowledge of principal normal curvatures, their directions and the tensor (Dupin indicatrix of this differential surface are necessary for description of contact of these surfaces. For description of surface geometry the first and the second surface fundamental tensor and a further methods of the differential geometry are used. A geometrical visualisation of obtained results of this analysis is made. Method and results of this study will be applied to contact analysis of tooth screw surfaces of screw machines.

  18. Nordic project food contact materials

    Li, Ågot; Tesdal Håland, Julie; Petersen, Jens Højslev

    countries have had a limited focus on the FCM area with the exception of Denmark and Finland. The aim of the project was therefore to control establishments producing, importing or using plastic food contact materials as well as to increase the knowledge of the inspectors performing these controls......Denmark, Finland, Faroe Islands, Iceland, Norway and Sweden have in 2013––2015 conducted a Nordic project on food contact materials. Food contact materials are used in all stages of food production and can be a general source of contamination. The food safety authorities in most of the Nordic....... The focus of the inspections was to control the declaration of compliance (DoC) for plastic food contact materials. The requirement for a Doc is mandatory in order to ensure that the FCM complies with the legislation. In addition some products were analyzed for phthalates....

  19. Transition metal contacts to graphene

    Politou, Maria, E-mail:; De Gendt, Stefan; Heyns, Marc [KU Leuven, 3001 Leuven (Belgium); imec, Kapeldreef 75, 3001 Leuven (Belgium); Asselberghs, Inge; Radu, Iuliana; Conard, Thierry; Richard, Olivier; Martens, Koen; Huyghebaert, Cedric; Tokei, Zsolt [imec, Kapeldreef 75, 3001 Leuven (Belgium); Lee, Chang Seung [SAIT, Samsung Electronics Co., Suwon 443-803 (Korea, Republic of); Sayan, Safak [imec, Kapeldreef 75, 3001 Leuven (Belgium); Intel Corporation, 2200 Mission College Blvd, Santa Clara, California 95054 (United States)


    Achieving low resistance contacts to graphene is a common concern for graphene device performance and hybrid graphene/metal interconnects. In this work, we have used the circular Transfer Length Method (cTLM) to electrically characterize Ag, Au, Ni, Ti, and Pd as contact metals to graphene. The consistency of the obtained results was verified with the characterization of up to 72 cTLM structures per metal. Within our study, the noble metals Au, Ag and Pd, which form a weaker bond with graphene, are shown to result in lower contact resistance (Rc) values compared to the more reactive Ni and Ti. X-ray Photo Electron Spectroscopy and Transmission Electron Microscopy characterization for the latter have shown the formation of Ti and Ni carbides. Graphene/Pd contacts show a distinct intermediate behavior. The weak carbide formation signature and the low Rc values measured agree with theoretical predictions of an intermediate state of weak chemisorption of Pd on graphene.

  20. Embodied Archives as Contact Zones

    Judit Vidiella


    Full Text Available This article proposes a reflection about affective politics from locating some theoretical and conceptual genealogies like «emotion», «affection», «zones of contact»…, that understand them as action and force fields. These contributions allow us to rethink the relation of affects with politics and strategies of archive linked to performance, and understood as zones of friction, collision, circulation and contact: performative writing, repertoire, memes…