Mass spectrometric detection and measurement of N2-(2′-deoxyguanosin-8-yl)PhIP adducts in DNA

Capillary column gas chromatography–electron-capture mass spectrometry (GC–MS) and microbore liquid chromatography–positive ion electrospray mass spectrometry (LC–MS) have been used to measure the carcinogenic, food-derived, heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) adducted at C-8 of deoxyguanosine in DNA. For GC–MS analysis, PhIP was released from adducted DNA by alkaline hydrolysis and analysed as the di(3,5-bistrifluoromethylbenzyl) derivative, while for LC–MS analysis, the nucleoside N2-(2′-deoxyguanosin-8-yl)PhIP was generated by enzymic digestion of DNA and analysed intact. A deuterated analogue of N2-(2′-deoxyguanosin-8-yl)PhIP was used as an internal standard in both assays, which each had a limit of quantification of 200 pg/500 μg DNA. The two methods were used to analyse DNA extracted from h1A2v2 cells and HCT116 cells that had been exposed to PhIP.