[Determination of biurea in flour and its products by liquid chromatography-tandem mass spectrometry].

A novel method was established for the determination and identification of biurea in flour and its products using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biurea was extracted with water and oxidized to azodicarbonamide by potassium permanganate. The azodicarbonamide was then derivatized using sodium p-toluene sulfinate solution. The separation was performed on a Shimpak XR-ODS II column (150 mm x 2.0 mm, 2.2 microm) using the mobile phase composed of acetonitrile and 2 mmol/L ammonium acetate aqueous solution (containing 0.2% (v/v) formic acid) with a gradient elution program. Tandem mass spectrometric detection was performed in multiple reaction monitoring (MRM) scan mode with a positive electrospray ionization (ESI(+)) source. The method used stable isotope internal standard quantitation. The calibration curve showed good linearity over the range of 1-20 000 microg/kg (R2 = 0.999 9). The limit of quantification was 5 microg/kg for biurea spiked in flour and its products. At the spiking levels of 5.0, 10.0 and 50.0 microg/kg in different matrices, the average recovery o biurea was 78.3%-108.0% with the relative standard deviations (RSDs) < or = 5.73%. The method developed is novel, reliable and sensitive with wide linear range, and can be used to determine the biurea in flour and its products.

Stone compositions in Turkey: an analysis according to gender and region.

OBJECTIVE: To evaluate the compositions of the kidney stones obtained from different regions of Turkey and to present the gender and regional differences. METHODS: The study included 6453 kidney stones obtained from patients from different parts of Turkey. All of the stones were obtained using ureterorenoscopy, percutaneous stone surgery, laparoscopic or open stone surgery, or extracorporeal shock wave lithotripsy. X-ray diffraction crystallography method was used for analysis. RESULTS: At the end of the analysis, 11 different stone types including calcium oxalate (Ca-ox) monohydrate (whewellite, COM), Ca-ox dihydrate (weddellite, COD), uric acid, cystine, struvite, biurea, xanthine brushite, quartz, whitlockite, and dahlite were determined either in pure or mixed conditions. Of the stones, 80.4% were Ca-ox (55.7% COM, 5.9% COD, 18.8% COM + COD), 4.8% uric acid, 3.1% cystine, and 3.3% were phosphate stones (dahlite, brushite, struvite, whitlockite). The remaining 8.4% of the stones were in mixed form with different combinations. Of the patients, 4411 were men (68.3%) and 2042 were women (31.7%). CONCLUSION: Ca-ox was the most frequently encountered stone type in our country as it is worldwide. The distribution of the other stone types is different than the other countries. The information about the structure of the stone has significant contribution to the understanding of the stone formation etiology, programming of the treatment process, and prevention of the recurrences. The study is significant in presenting the stone profile of Turkey.

Isobutylidenediurea degradation by Rhodococcus erythropolis.

A new enzyme (isobutylidenediurea amidinohydrolase) catalyzing the hydrolysis of isobutylidenediurea (a condensation product of urea and isobutyraldehyde widely used as a slow-release nitrogeneous fertilizer) was characterized from a strain of Rhodococcus erythropolis. The enzyme was purified 1,250-fold to apparent homogeneity and shown to hydrolyze the fertilizer to urea and isobutyraldehyde at a molar ratio of 2: 1. No activity was observed with ureido- or other structurally related compounds. Its molecular mass was determined by native polyacrylamide gelelectrophoresis and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry to be 15 kDa (+/-2 kDa) and 16.4 kDa, respectively. Growth of the bacterium in the presence of isobutylidenediurea led to an increased expression of the constitutively synthetized enzyme.

Azodicarbonamide: methods for the analysis in tissues of rats and inhalation disposition.

1. A method has been developed for measuring azodicarbonamide (ADA) and its metabolite biurea in tissues of rat. The method is based on the reaction of ADA with triphenylphosphine; the derivative so formed was isolated and quantified using reversed-phase h.p.l.c. Quantification was by u.v. detection with 14C-ADA as internal standard. Biurea was measured by oxidation to ADA, followed by treatment as described above. 2. When biurea was added to tissues at 100-400 micrograms, recoveries of 92-125% were observed. In contrast, recoveries of ADA added to tissues were generally much less than 100% and could not be reliably determined. The inability to quantify ADA added to tissues was ascribed to its rapid and facile reduction by tissue sulphydryl groups. 3. When rats were exposed to ADA aerosol concentrations of 200, 100, 50 and 0 mg/m3 for 13 weeks by inhalation, a non-linear dose-dependent accumulation of biurea was observed in lungs. No ADA was detected in lungs. Neither biurea nor ADA could be detected in kidneys.

The determination of biurea in the presence of azodicarbonamide by HPLC.

Azodicarbonamide (ADA), a solid blowing agent used in the manufacture of plastics, has been selected for inhalation toxicity testing by the National Toxicology Program. To test for decomposition of ADA during aerosolization, an HPLC method was developed to quantitate the relative amounts of one possible degradation product, biurea, in bulk samples and filter samples collected after aerosolization. The method uses a C18 column with 10-micron particles, UV monitoring at 190 nm for biurea and 425 nm for ADA, and a mobile phase of 100% water. Quantitation is with 14C-labeled biurea and ADA as external standards. The assay was validated by spiking bulk ADA with projected levels of 1, 2, and 3% biurea. Levels of biurea bound in both bulk and filter-collected aerosol samples of ADA were both 0.50%, with relative standard deviations of 13 and 26%, respectively.