Determination of N-nitroso compounds by high-performance liquid chromatography with postcolumn reaction and a thermal energy analyzer.

Carcinogenic nonvolatile N-nitroso compounds have been difficult to determine in foods and other consumer products because of the incompatibility of aqueous high-performance liquid chromatography (HPLC) mobile phases with the thermal energy analyzer (TEA), a sensitive and selective detector for N-nitroso compounds. A postcolumn technique has been developed that permits the use of aqueous mobile phases with an interfaced liquid chromatograph/TEA. This system was linear from 3.5 to 900 ng of N-nitrosoproline injected. Coefficients of variation of 3.0 and 5.1%, respectively, were obtained when N-nitrosoproline and N-nitrosotrimethylurea were repeatedly injected at the 80- to 90-ng level. Mixtures of volatile and nonvolatile N-nitroso compounds as well as N-nitrosodipeptides were separated and quantitated by HPLC/TEA with a water/acetonitrile gradient.