Sample records for biureas

  1. The determination of biurea: A novel method to discriminate between nitrofurazone and azodicarbonamide use in food products

    International Nuclear Information System (INIS)

    Mulder, P.P.J.; Beumer, B.; Rhijn, J.A. van


    Recently doubts have arisen on the usefulness of semicarbazide as marker residue for the illegal use of the antibiotic nitrofurazone (NFZ) in aquaculture and poultry production. Most notably azodicarbonamide (ADC) has been implicated as an alternative source of semicarbazide. ADC is used in some countries as a dough conditioner at concentrations up to 45 mg kg -1 . The use of ADC-treated flour or dough in coated or breaded food products may generate false non-compliant results in the analytical method for nitrofurazone metabolites, which is currently in use. During the dough preparation process ADC is largely reduced to biurea, which can be considered as an appropriate marker residue of ADC. Thus far no methods have been published for the determination of biurea in food commodities. Due to its polar nature it is very difficult to generate sufficient retention on conventional C 18 HPLC columns. With a TSK amide HILIC type column good retention was obtained. A straightforward extraction-dilution protocol was developed. Using a mixture of dimethyl formamide and water biurea was nearly quantitatively extracted from a variety of fresh, coated and processed products. Mass spectrometric detection was performed with positive electrospray ionisation. The sensitivity and selectivity of the mass spectrometer for biurea was very good, allowing detection at concentrations as low as 10 μg kg -1 . However, in some extracts severe ion suppression effects was observed. To overcome the implications of ion suppression on the quantitative performance of the method an isotopically-labelled biurea internal standard was synthesized and incorporated in the method. The method developed can be used effectively in nitrofurazone analysis to eliminate the risk of false non-compliant results due to the presence of azodicarbonamide-treated components in the food product

  2. Fate of inhaled azodicarbonamide in rats

    International Nuclear Information System (INIS)

    Mewhinney, J.A.; Ayres, P.H.; Bechtold, W.E.; Dutcher, J.S.; Cheng, Y.S.; Bond, J.A.; Medinsky, M.A.; Henderson, R.F.; Birnbaum, L.S.


    Azodicarbonamide (ADA) is widely used as a blowing agent in the manufacture of expanded foam plastics, as an aging and bleaching agent in flour, and as a bread dough conditioner. Human exposures have been reported during manufacture as well as during use. Groups of male F344/N rats were administered ADA by gavage, by intratracheal instillation, and by inhalation exposure to determine the disposition and modes of excretion of ADA and its metabolites. At 72 hr following gavage, 30% of the administered ADA was absorbed whereas following intratracheal instillation, absorption was 90%. Comparison between groups of rats exposed by inhalation to ADA to achieve body burdens of 24 or 1230 micrograms showed no significant differences in modes or rates of excretion of [ 14 C]ADA equivalents. ADA was readily converted to biurea under physiological conditions and biurea was the only 14 C-labeled compound present in excreta. [ 14 C]ADA equivalents were present in all examined tissues immediately after inhalation exposure, and clearance half-times on the order of 1 day were evident for all tissues investigated. Storage depots for [ 14 C]ADA equivalents were not observed. The rate of buildup of [ 14 C]ADA equivalents in blood was linearly related to the lung content as measured from rats withdrawn at selected times during a 6-hr inhalation exposure at an aerosol concentration of 25 micrograms ADA/liter. In a study extending 102 days after exposure, retention of [ 14 C]ADA equivalents in tissues was described by a two-component negative exponential function. The results from this study indicate that upon inhalation, ADA is rapidly converted to biurea and that biurea is then eliminated rapidly from all tissues with the majority of the elimination via the urine

  3. Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3. [photolysis products (United States)

    Hubbard, J. S.; Voecks, G. E.; Hobby, G. L.; Ferris, J. P.; Williams, E. A.; Nicodem, D. E.


    Ammonium cyanate is identified as the major product of the photolysis of gaseous NH3-CO mixtures at 206.2 or 184.9 nm. Lesser amounts of urea, biurea, biuret semicarbazide, formamide and cyanide are observed. A series of 18 reactions underlying the formation of photolysis products is presented and discussed. Photocatalytic syntheses of C-14-urea, -formamide, and -formaldehyde are carried out through irradiation of (C-14)O and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. The possible contributions of the relevant reactions to the abiotic synthesis of organic nitrogen compounds on Mars, the primitive earth, and in interstellar space are examined.

  4. Component Analysis of Deposits in Selective Catalytic Reduction System for Automotive Diesel Engine

    Directory of Open Access Journals (Sweden)

    Zhu Neng


    Full Text Available In this paper, deposits in exhaust pipes for automotive diesel engines were studied by various chemical analysis methods and a kind of analysis process to determine the compositions of organic matter was proposed. Firstly, the elements of the deposits were determined through the element analysis method. Then using characteristic absorption properties of organic functional groups to the infrared spectrum, the functional groups in the deposits were determined. Finally, by GC-MS (gas chromatography - mass spectrometry test, the content of each main component was determined quantitatively. Element analysis results indicated that the deposits adsorbed metal impurities from fuel oil, lubricating oil, mechanical wear and urea water solution. The result of GC-MS test showed that the area percentage of cyanuric acid was the biggest (about 85%, the second was urea (about 4%, and the content of biuret and biurea was scarce.