Gas chromatography-mass spectrometry analysis of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in urine and feces.

A method has been developed to measure levels of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) excreted in urine and feces. The method involves organic solvent extraction, derivatization to form electron-capturing bis-pentafluorobenzyl derivatives, and analysis by gas chromatography-negative ion chemical ionization mass spectrometry using a deuterium-labeled internal standard. The method can detect PhIP at levels of less than 1 ng/g in rat urine (5 ng/24 hr) and 5 ng/g (wet weight) in rat feces (50 ng/24 hr). Sprague-Dawley rats given a single 50 micrograms dose of PhIP by gavage excreted an average of 0.6% of the dose in the urine and 25% of the dose in the feces as unchanged PhIP, in the first 4 days after treatment. To make this method applicable for the analyses of biological fluids of PhIP-exposed human subjects, it is now being improved by using immunoaffinity chromatography.