Detection and measurement of MeIQx in human urine after ingestion of a cooked meat meal

A gas chromatographic - mass spectrometric assay has been developedfor the measurement of 2-ainino-3,8-dimethylimidazo 4,5-fquinoxaline(MeIQx)in urine. The method employs capillary column gas chromatography,electron capture negative-ion chemical ionization mass spectrometry,a stable isotope-labelled analogue of MeIQx as internal standardand has a limit of detection of 5 pg MeIQx/ml urine. Six subjectsconsumed a fried beef meal and urine was collected before andafter this event. While no MeIQx could be detected in urinecollections made prior to meat consumption, the 12-h urine collectionsof all six subjects made after the meal contained the amine.When the amounts of MeIQx measured in the urine collectionswere compared to the quantities of amine ingested in the friedbeef, it was found that 1.8–4.9% of the oral dose wasexcreted unchanged in urine. Metabolic studies in animals leadus to believe that MeIQx in the diet is efficiently absorbedand extensively biotransformed.