Stephen W. Seaman

Methyl carbamate and ethyl carbamate in alcoholic beverages and other fermented foods

Abstract Varying but low levels of ethyl carbamate (EC), also known as urethane, are known to be present in various alcoholic beverages and many other fermented foods. Very little data, however, are available on the levels of methyl carbamate (MC) in such products. In this study, 48 samples of various alcoholic beverages, 12 of bread and toast, 10 of soy sauce, and 14 of yogurt and buttermilk were analyzed for both EC and MC by a newly developed method using gas chromatography thermal energy analyzer (N-mode) for detection and gas chromatography high resolution mass spectrometry for confirmation. Only traces (mostly μ g/kg) of MC were detected in some of the products in each category, but much higher levels of EC were detected in some sherries (up to 69 μg/kg), whiskies (up to 247 μg/kg), fruit brandies (up to 432 μg/kg), soy sauces (up to 59 μg/kg), and toasts (up to 29 μg/kg). The levels of EC in the dark toasts (still edible) were significantly higher than those present in the breads or light toasts.

A method for the determination of methyl carbamate and ethyl carbamate in wines

A method is described for the simultaneous determination of methyl carbamate (MC) and ethyl carbamate (EC) in wines that is based on: (a) extraction of the sample with dichloromethane using an extraction tube or an alumina-Celite column, (b) concentration of the extract to a small volume, and (c) determination by gas-liquid chromatography-thermal energy analyser (N-mode). The method is highly sensitive (1-2 ng/ml), accurate (recoveries greater than 80%), and precise (CV, 5-10%). Nineteen of 27 samples of wines analysed contained traces (up to 2.7 ng/ml) of MC, and most contained EC (up to 70 ng/ml). Wines treated in the laboratory with 200 ppm dimethyl pyrocarbonate (DMPC)-a cold sterilant recently approved for use in wines-indicated that such a treatment may increase the MC contents of the wines to 10 ng/ml. Additional studies suggested that formation of MC in DMPC-treated wines is dependent on both pH and ammonia content of the wines. The identity of MC in a few selected samples was confirmed by gas-liquid chromatography-high resolution (10 K) mass spectrometry. The natural low levels of MC found in these wines are not considered to pose a risk to human health.

Determination of non-volatile N-nitrosamines in baby bottle rubber nipples and pacifiers by high-performance liquid chromatography-thermal energy analysis.

A method is described for the determination of non-volatile N-nitrosamines in baby bottle rubber nipples and pacifiers. It consists of extraction of the sample with dichloromethane in the presence of ascorbyl palmitate (an inhibitor of artifactual formation of nitrosamines), clean-up on silica or basic alumina, and final analysis by high-performance liquid chromatography-thermal energy analysis, a technique which is highly specific for N-nitroso compounds. The method worked well for the determination of four rubber-related non-volatile nitrosamines, namely, N-nitrosomethylphenylamine, N-nitrosoethylphenylamine, N-nitrosodicyclohexylamine, and N-nitrosodibenzylamine (recoveries from spiked samples greater than 80%; detection limit, ca. 5 micrograms/kg for each). Eighteen out of twenty four samples analyzed were found to contain varying levels (mean, 41 micrograms/kg; range, 8-146 micrograms/kg) of N-nitrosodibenzylamine. The identity of the compound was confirmed by gas chromatography-thermal energy analysis as well as by gas chromatography-mass spectrometry analyses.

Nitrosamines in cured pork products packaged in elastic rubber nettings: An update

Previous research has shown that traces to fairly high levels of certain N-nitrosamines can form in cured pork products packaged in elastic rubber nettings. The N-nitrosamines are formed due to the interaction of nitrite additive in the meat and amine additives in the rubber that are used as accelerators in the curing of rubber. This paper briefly reviews earlier findings and presents some recent results. Of twenty samples of such pork products analyzed, one was negative, six contained 12–32 μg/kg levels of N-nitrosodibenzylamine (NDBZA) but no N-nitrosodi-n-butylamine (NDBA), and the remaining samples contained appreciable levels of both the compounds (NDBA up to 48 μg/kg and NDBZA up to 520 μg/kg). These results suggest that the problem of N-nitrosamine formation in these products is yet to be resolved.

Prevention of artifactual formation of nitrosamines during the analysis of baby bottle rubber nipples

It has been found that considerable amounts of nitrosamines may be formed as artifacts during the analysis of rubber nipples by a method that involves Soxhlet extraction of the samples with dichloromethane. The extent of such formation was monitored by incorporating morpholine as a marker amine and studying the formation of nitrosomorpholine, which varied between 9 and 80 ng per analysis depending on the type of sample analysed and the brand of dichloromethane used. The problem could be minimised by pre-testing dichloromethane for its N-nitrosation potential and by incorporating propyl gallate, an N-nitrosation inhibitor, in the method.