Robert C. Doerr

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.

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.