N-nitrosamine analysis in foods: N-nitrosoamino acids by high-performance liquid chromatography/thermal energy analysis and total N-nitroso compounds by chemical denitrosation/thermal energy analysis.

The total N-nitroso content of foods can be measured by chemical denitrosation and chemiluminescent detection of the eliminated nitric oxide. Appropriate procedures substantially reduce the 'system response' to the denitrosating agent, so that N-nitroso group contents down to 10 micrograms/kg can be measured on a one-gram sample. Using N-nitrosamine standards added to beer, the coefficients of variation are approximately 10% and 5% at N-nitroso contents of 19 and 94 micrograms/kg, respectively. In cured meats, the coefficient of variation for unidentified N-nitroso compounds is 26% for a 0.3-g sample containing 600 micrograms/kg. Some interference from non-nitroso compounds is possible, but, in some commodities at least, these interfering compounds are not detectable. Conditions have been established that allow measurement of N-nitrosoamino acids in foods using a high-pressure liquid chromatograph interfaced to a Thermal Energy Analyzer, without the need for prior derivatization. After extraction of lipids with hexane, nitrosoamino acids are extracted with ethyl acetate and subjected to appropriate clean-up stages prior to high pressure liquid chromatography on Microbondapak CN with a hexane:ethanol:acetic acid mobile phase and Thermal Energy Analyzer detection. Recoveries from cured meat are in the 55-75% range for N-nitrososarcosine, N-nitrosoproline and N-nitrosohydroxyproline; elution is complete within seven minutes.