Measurement of MeIQx and DiMeIQx in fried beef by capillary column gas chromatography electron capture negative ion chemical ionisation mass spectrometry.

A gas chromatographic-mass spectrometric assay has been developed for the simultaneous measurement of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) in fried beef. The method employs capillary column gas chromatography, electron capture negative ion chemical ionisation mass spectrometry and a stable isotope labelled analogue of MeIQx (the synthesis of which is described) as common internal standard. Two patties of lean minced beef which had been cooked separately were analysed and found to contain both compounds (patty 1-2.4 ng MeIQx/g meat, 1.2 ng DiMeIQx/g meat; patty 2-1.3 ng MeIQx/g meat, 0.5 ng DiMeIQx/g meat). Neither compound was present in the meat prior to cooking.