W. Fiddler

Role of strong ion exchange resins in nitrosamine formation in water

Abstract N-Nitrosodimethylamine (NDMA) was formed when tap water was passed through a column containing only the anion exchange resin, thereby indicating that nitrosamine (NA) formation by the conventional acid catalyzed nitrosation reaction, as would be expected in the case of a mixed strong anion and cation resin system, was not the primary mechanism. The quaternary ammonium ion of the strong anion resin may be the amine precursor for NA formation. Strong anion and strong cation resins (Amberlite and Dowex brands ‡ ) were ineffective in concentrationg low levels of NDMA that were added to the influent. Accumulation of extremely low levels of NA already present in the water, therefore, also did not contribute importantly to the concentration of NA found in deionized water. In addition, the normal levels of cations and anions in water, and heavy metal ions were also not primarily responsible for this occurrence. There was, however, an unknown substance(s) in tap water that promoted NA formation. This unknown soluble substance(s) can be removed by activated carbon treatment or degassing techniques.

Dimethylnitrosamine in frankfurters

Summary Samples of frankfurters from eight large producers were analysed for N,N -dimethylnitrosamine (DMNA), using gas chromatography, with an alkali-flame ionization detector for quantitative analysis and a mass spectrometer for confirmation. Only trace levels of a compound that was apparently DMNA were found in the products of five manufacturers. In one further sample a somewhat higher level of a compound presumed to be DMNA was found but again this could not be confirmed. Two samples of frankfurters, containing 84 and 11 μg DMNA/kg respectively, were found among 22 samples from one producer, and one sample out of 12 from another producer contained 48 μg DMNA/kg. These were confirmed. High sodium nitrite values found in the frankfurters from one manufacturer could not be correlated with nitrosamine formation.

Determination of flumequine and oxolinic acid in fortified chicken tissue using on-line dialysis and high-performance liquid chromatography with fluorescence detection

Abstract Isolation of the fluoroquinolones, flumequine and oxolinic acid, from fortified chicken liver was achieved using liquid–liquid extraction, aqueous on-line dialysis and trace enrichment. Dialysis, trace enrichment and column switching were performed using the ASTED system. Separation of the isolated compounds in the tissue extracts was performed using reversed-phase HPLC and fluorescence detection. This procedure yielded excellent mean recoveries at the 50, 25, 10 and 5 ng/g spiking levels for flumequine (94–96%; 4–9% R.S.D.) and at the 25 and 5 ng/g spiking levels for oxolinic acid (98–99%; 4–6% R.S.D.). Clean chromatograms were obtained, allowing detection of 5 ng/g flumequine and 2.5 ng/g oxolinic acid to be easily made. Due to its lower organic solvent consumption, automation and on-line capabilities, this method may be a suitable replacement for conventional chemical extraction techniques for drug residues in animal tissues.

Determination of N-nitrosoproline at the nanogram level.

Two sensitive detection systems are described for the quantitative determination of a nonvolatile nitrosamine, nitrosoproline. One procedure involves denitrosation followed by derivatization of amino product, proline, with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl). The highly fluorescent NBD-proline compound formed is then identified and quantitated by either thin-layer chromatography or high-pressure liquid chromatography (HPLC). In the second system, the volatile methyl ester of the intact nitrosoproline is prepared, then detected by gas-liquid chromatography (GLC), and confirmed by combined gas-liquid chromatography and mass spectrometry (GLC-MS). Both methods permit the quantitative detection of less than 10 ng of nitrosoproline. However, the HPLC fluorescence technique is approximately ten times as sensitive as the GLC method.

The presence of dimethyl- and diethyl-nitrosamines in deionized water

Summary Twenty seven of 42 samples of water exposed to deionizing resins contained from 0.03 to 0.34 ppb ( μ g/litre) dimethylnitrosamine, as determined by gas-liquid chromatography combined with thermal energy analysis, a detection method claimed to be specific for nitrosamines. Twelve of these 27 samples, mainly from water obtained after resin regeneration, were confirmed as containing dimethyl-nitrosamine by gas-liquid chromatography-high resolution mass spectrometry. Two samples of water deionized at the Center, were confirmed as containing 0.33 and 0.83 diethylnitrosamine as well as the dimethylnitrosamine. The origin of these nitrosamines is unknown at present.

Potential artifact formation of dioxins in ball clay during supercritical fluid extraction

Earlier surveys indicate that meat, fish and dairy products are the principal source of polychlorinated dibenzo-p-dioxin (PCDD) exposure in the diet. A recent finding by others of PCDDs in chickens that consumed a feed containing PCDD led to the finding of ball clay, an anti-caking agent, as the source. Supercritical fluid extraction (SFE) was studied as a means to isolate PCDDs from commercial ball clays using GC-electron capture detection (muECD) as a means to screen for these contaminants. The finding of ng/g amounts and recoveries >100% in several samples of ball clay containing octachlorodibenzo-p-dioxin (OCDD) suggested that PCDD may form artifactually as a result of analysis. Studies on pentachlorophenol (PCP) fortified ball clay were carried out by SFE and soxhlet extraction and the results compared. The values obtained by SFE were considered more problematic. The results obtained from ball clay suggest that precautions need to be exercised when using SFE to analyze for dioxins in solid samples containing chlorophenols.

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.

Kinetic study on the nitrosation of dibenzylamine in a model system

A kinetic study of the formation of N-nitrosodibenzylamine (NDBzA), from the nitrosation of dibenzylamine (DBzA) by sodium nitrite, was performed in a model system under conditions (temperature, pH) that are similar to those encountered in the industrial production of hams processed in elastic rubber nettings. The nitrosation reaction was carried out in a KH2PO4 buffer (0.5 M) at pH 5.8 and at a temperature of 69 degrees C. Since DBzA is insoluble in an aqueous buffer system, a non-ionic surfactant, Tween 20, was used as a solubilizing agent. The nitrosation reaction exhibited first-order kinetics with respect to DBzA and second-order kinetics with respect to nitrite. The calculated rate constant was 4.7 +/- 0.5 M-2/min. The pH profile of NDBzA formation was also determined. The optimal pH of NDBzA formation, 3.12, was close to the pKa of nitrous acid (HNO2, pKa = 3.1).

Dimethylnitrosamine in souse and similar jellied cured-meat products

Abstract Dimethylnitrosamine was found in eight of ten samples of commercial souse and similar gelatin-containing cured-meat products at levels ranging from 3 to 63 μg/kg. One of the samples was also found to contain 19 μg nitrosopyrrolidine/kg. There appeared to be no correlation between residual levels of sodium nitrite and the nitrosamine concentration. The nitrosamines were determined quantitatively by gas-liquid chromatography (glc) using an alkali flame ionization detector and the analyses were confirmed by glc-high resolution mass spectrometry.