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Biomedical subjects

W Fiddler

Publications and source records attributed to W Fiddler.

At least 55 records · Page 3Linked to original sources
PubMedDate not supplied

Apparent mutagenicity of N-nitrosothiazolidine caused by a trace contaminant.

The identification of N-nitrosothiazolidine (NTHZ) in smoked meat products prompted us to evaluate this compound for mutagenicity by the Salmonella assay. NTHZ was prepared in 99 + % purity by the nitrosation of the cysteamine-formaldehyde reaction mixture without isolation and purification of the resulting amine, and from thiazolidine, directly. Mutagenic activity was observed with TA100 without metabolic activation in the former, but not the latter preparation. An examination of the precursors, reaction intermediates, and HPLC separation of the NTHZ from the mutagenic product demonstrated that the genotoxic activity resulted from a synthesis-produced trace contaminant.

Animals↗
PubMedDate not supplied

Isolation of chloramphenicol from whole eggs by supercritical fluid extraction with in-line collection.

Egg consumption, at more than 65 billion per year in the United States, represents a potentially significant source of exposure to drug residues, particularly if the laying hens are treated with antimicrobial compounds or fed a diet containing medicated feed. Residues resulting from the use of chloramphenicol (CAP) is especially problematic if this compound is not used in accordance with national registration, e.g., for the control of Salmonella microorganisms in poultry. The most commonly used methods for the determination of CAP in biological samples require the use of large amounts of organic solvent. As a result, a less solvent intensive supercritical fluid extraction (SFE) method was developed for CAP in whole chicken eggs, and the results were compared with those for a solvent extraction procedure. In the SFE method, the egg sample is extracted with supercritical CO2 (without a modifier) at 10,000 psi (680 bar), 80 degrees C, and an expanded gas flow rate of 3.0 L/min to a total volume of 150 L. The CAP is trapped in-line on a Florisil sorbent bed. The CAP is eluted post-SFE by using the liquid chromatographic mobile phase solvent (water-methanol), and determined on a C8 column with ultraviolet detection at 280 nm. Recovery from eggs fortified at the 10 ppb level (n = 6) was 81.2 +/- 4.3%. To obtain eggs containing incurred CAP, hens were given a single daily dose of 75 mg CAP (orally by gelatin capsule) for 2 consecutive days, and the eggs were collected over a 12-day period. The mean value for "normally incurred" CAP in the eggs (n = 17) analyzed by SFE ranged from none detected to 174.5 ppb, with an overall mean of 60.5 ppb, compared with a mean of 60.4 ppb for the solvent extraction method. No significant difference in results was found between methods. However, the SFE method is more rapid, uses less solvent, and gives recoveries similar to those for the solvent extraction method, making it ideal for regulatory monitoring.

Animals↗
PubMedDate not supplied

Gas chromatographic method for determination of dimethylamine, trimethylamine, and trimethylamine oxide in fish-meat frankfurters.

A method is described for analysis of minced fish-meat and surimi-meat frankfurters for dimethylamine (DMA), trimethylamine (TMA), and trimethylamine oxide (TMAO) using a headspace-gas chromatographic technique. After simple acid extraction and addition of NaOH, the headspace was directly injected into a gas chromatograph by a gas-tight syringe. DMA and TMA were separated on a Chromosorb 103 column and detected by a flame ionization detector. TMAO was measured as TMA after Zn reduction. Repeatability of the method for DMA, TMA, and TMAO was 6.6, 1.0, and 18.8 ppm, respectively. The method was applicable to Alaska pollock-meat and Atlantic menhaden-meat frankfurters, unwashed, and washed mince and surimi.

Analysis of Variance↗
PubMedDate not supplied

Gas chromatographic-chemiluminescence method for determination of volatile N-nitrosamines in minced fish-meat and surimi-meat frankfurters: collaborative study.

A collaborative study was carried out on a solid-phase extraction method for separating volatile N-nitrosamines, particularly N-nitrosodimethylamine (NDMA), from combination minced fish or surimi-meat frankfurters with detection by gas chromatography-chemiluminescence (thermal energy analyzer). The results from the 10 collaborators were evaluated using the most recent AOAC guidelines for determining outliers and for the analysis of variance. For NDMA, repeatability standard deviations, sr, ranged from 0.56 to 2.25; repeatability relative standard deviations, RSDr, ranged from 8.9 to 11.5%. Reproducibility standard deviations, SR, for NDMA ranged from 1.40 to 6.49, and reproducibility relative standard deviations, RSDR, ranged from 24.2 to 28.9%. Our data compared favorably to the reproducibility (RSDR) curve of Horwitz. The method has been adopted official first action by AOAC.

Chromatography, Gas↗
PubMedDate not supplied

Determination of ten N-nitrosoamino acids in cured meat products.

A rapid, sensitive, and accurate solid-phase extraction method was developed for the measurement of 10 N-nitrosoamino acids (NAAs) in cured meat products. In the procedure, the comminuted meat was mixed with sulfamic acid and Celite, and then added to a glass column containing anhydrous sodium sulfate. The column was washed with pentane, and the NAAs were eluted with ethyl acetate. The eluate was concentrated, then derivatized with diazomethane followed by acetic anhydride-pyridine reagent. The NAA methyl esters and their acylated hydroxy derivatives were separated by gas chromatography on a DB-5 fused silica capillary column and quantitated with a thermal energy analyzer, a chemiluminescence detector specific for nitric oxide derived from the thermal denitrosation of nitrosamines. Recovery of 10 of the NAAs exceeded 75% at the 10 ppb level. The method is applicable to a wide range of cured meat products.

Amino Acids↗
PubMedDate not supplied

Investigations on N-nitrosopyrrolidine in dry-cured bacon.

Dry-cured or "country-style" bacon is a low volume specialty product typically made by small producers whose production practices vary widely. These practices include the direct application of dry-cure formulations containing varying concentrations of salt, sugar, flavoring agents, sodium nitrite, and sometimes sodium nitrate, and the use of lengthy curing and processing times. Because of the possibility of generating higher levels of N-nitrosopyrrolidine (NPYR) after frying in this product type compared with pump-cured bacon, an investigation was carried out on dry-cured bacon obtained from cooperating state or federally inspected establishments. Three different samples from each of the 16 plants were analyzed. Only one sample from each of 2 different producers exceeded the Food Safety and Inspection Service (FSIS) action level of 17 ppb NPYR, indicating that the majority of samples tested were in compliance. A significant correlation (P less than 0.01) was found between residual NaNO2 prior to frying and NPYR after frying. The elimination of added nitrate in the dry-cure formulations is recommended.

Animals↗
PubMedDate not supplied

Determination of volatile N-nitrosamines in frankfurters containing minced fish and surimi.

A method was developed to quantitatively measure volatile N-nitrosamines, particularly N-nitrosodimethylamine (NDMA), in cured minced fish or surimi-meat frankfurters. This method is free from artifact formation. First, 2 dry solid-phase extraction columns are prepared. Solvent is passed through the top column containing the fish-meat into a second column containing acid Celite. The eluate from the Celite column is then passed through a third column containing silica gel. Nitrosamines are eluted from the acid Celite column and then from the silica gel column into the same receiver. Recovery of the internal standard, N-nitrosoazetidine, added at the 10 ppb level, was 86.5%. In addition, a few samples of nitrite-treated salmon (lox) were also tested for N-nitrosamines. The results show that the method is applicable to samples containing nitrite-treated fish and fish-derived products.

Animals↗
PubMedDate not supplied

Determination by liquid chromatography with electrochemical detection of cysteamine and cysteine, possible precursors of N-nitrosothiazolidine.

A method is described that is selective, sensitive, rapid, and accurate for the quantitative measurement in meat products of both cysteamine and cysteine, potential precursors for N-nitrosothiazolidine (NTHZ) and N-nitrosothiazolidine-4-carboxylic acid (NTHZC), respectively. In general, a ground meat sample is homogenized with acetonitrile-formate buffer in the presence of dithiothreitol, and then is centrifuged, filtered, and recentrifuged in a disposable microfilter. The thiols are quantitated by liquid chromatography using an amperometric detector equipped with a gold/mercury electrode, operated in the oxidative mode. Cysteamine was found in 6 of 20 samples of raw pork belly in concentrations ranging from 150 to 450 ppb, and cysteine was found in all samples in concentrations ranging from 2.4 to 36.5 ppm. Analysis for the thiols and their corresponding nitrosamines--NTHZ and NTHZC--of bacon before and after processing showed no correlation between cysteamine and cysteine levels before processing nor with nitrosamine levels after processing. Liquid chromatography with electrochemical detection was found to be an extremely selective technique to measure the 2 free sulfhydryl compounds in a complex food substrate.

Animals↗
PubMedDate not supplied

Effect of N-nitrosothiazolidine-4-carboxylic acid on formation of N-nitrosothiazolidine in uncooked bacon.

N-Nitrosothiazolidine-4-carboxylic acid (NTHZC) was recently identified in a variety of smoked fish and cured meat products. While the toxicological properties of NTHZC are currently unknown, it has been speculated that N-nitrosothiazolidine (NTHZ) in fried bacon may be caused in part by decarboxylation of NTHZC. A limited survey of uncooked cured meat products failed to demonstrate any correlation between levels of NTHZC and NTHZ. However, NTHZC levels were significantly higher, ranging from 8 to 1400 ppb, than the corresponding NTHZ levels, which ranged from less than 2 to 18 ppb. Decarboxylation of NTHZC to NTHZ in a model system occurs at 110 degrees C, which is significantly higher than the average bacon processing temperature of 54 degrees C, but lower than the normal frying temperature of 177 degrees C recommended for bacon. Results from both model system and frying experiments with NTHZC and its precursors suggest that NTHZC decarboxylation to NTHZ is not the principal pathway to NTHZ formation in uncooked bacon.

Animals↗
PubMedDate not supplied

Confirmation of N-nitrosodimethylamine and N-nitrosopyrrolidine in foods by conversion to their nitramines with pentafluoroperoxybenzoic acid.

A method is presented, wherein concentrated dichloromethane extracts from malt, beer, and nonfat dried milk powder containing N-nitrosodimethylamine (NDMA), and fried dry-cured and pump-cured bacon containing NDMA and N-nitrosopyrrolidine (NPYR) undergo 3N HClO4-Celite microcolumn cleanup followed by peroxidation with pentafluoroperoxybenzoic acid, a stable solid peroxyacid, to N-nitrodimethylamine and N-nitropyrrolidine, as an aid to nitrosamine confirmation. The nitramine-containing solution underwent further cleanup with 6N HClO4-Celite and acid alumina-6% H2O microcolumns for subsequent analysis by gas chromatography interfaced with thermal energy analyzer and 63Ni electron capture detectors. With a 20 g sample, 1 ppb NDMA and 2.5 ppb NPYR could be confirmed by this method. The extract can be concentrated further before analysis, so the detection level can be reduced to less than 1 ppb NDMA and 1 ppb NPYR.

Chemical Phenomena↗