Stable isotope dilution quantification of mutagens in cooked foods by combined liquid chromatography-thermospray mass spectrometry.

A method of general applicability for the detection and quantification of mutagens in cooked foods at the ppb level is presented. A minimal sample prefractionation is employed and [Me-2H3]-labeled analogs of the compounds of interest are added for identification and quantification of mutagens by accurate measurement of chromatographic retention (K') in reverse-phase high-performance liquid chromatography (HPLC), and by measurement of the ratio of response of the protonated molecular ions of analyte and internal standard by directly coupled liquid chromatography-mass spectrometry (LC/MS). Initial application is demonstrated in the analysis of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) in broiled salmon. Measured levels of IQ and MeIQ in broiled salmon flesh were 0.3-1.8 ppb and 0.6-2.8 ppb, respectively, and for the skin of broiled salmon 1.1-1.7 ppb and 1.5-3.1 ppb, respectively. Results on cooked beef and sardine are also reported.