John W. Pensabene

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.

Analysis of human blood for volatile N-nitrosamines by gas chromatography−chemiluminescence detection

A method was developed to separate and measure trace levels of volatile N-nitrosamines (NAs) in human blood that either eliminated or accounted for in vitro artifactual formation of N-nitrosodimethylamine (NDMA) through the use of water blanks, added inhibitor (ascorbic acid) and added morpholine. The absolute minimum detectable limit was 8 pg; minimum level of reliable measurement was 0.05 microgram/kg for a 20-g blood specimen. Recovery of NDMA from blood was 93 +/- 5%. Coefficient of variation was 25%. Bloods from 242 people were analyzed for volatile NAs. NDMA was the only NA found. Positive specimens were presumptively confirmed by their non-detection after ultraviolet photolysis and/or mass spectrometry. This paper presents additional evidence that in vivo NA formation occurs.

Indole and skatole in fresh pork as possible markers of fecal contamination

Zero-tolerance levels for fecal contamination on beef, pork, and poultry have been proposed because of outbreaks of foodborne illnesses associated with pathogenic microorganisms from this source. As a result, changes in the current meat inspection system will have to include means other than visual inspection of the carcass to ensure the absence of contamination. While the principal need is for rapid, in-plant microbial testing methods, there is also a need for chemical-instrumental methods. A rapid solid-phase extraction method was developed to measure indole and skatole in porcine meat using a gas chromatograph interfaced with a chemiluminescence detector. The minimum detectable level for both compounds was 10 ppb. Results from the analysis of contaminated pork showed that this approach may have limited value in the assessment of fecal contamination in pork samples, since not all of the samples had detectable levels of either indole or skatole.