Detection of in vivo formed DNA adducts at the part-per-billion level by capillary liquid chromatography/microelectrospray mass spectrometry

Capillary liquid chromatography/microelectrospray mass spectrometry has bee n applied to the detection of deoxyribonucleoside adducts of the food-deriv ed mutagen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) from in vivo source s. Adjustments were made to a previously described methodology such that an alyte detection could be improved by nearly 2 orders of magnitude. These ad justments included changing the electrospray ionization sprayer configurati on, increasing the sample injection volume, improving the solid-phase extra ction procedure, and increasing peak efficiency by modifying chromatographi c conditions. while this scheme for improving analyte detection was targete d for DNA adducts, it could be applied to almost any LC/MS methodology wher e sensitive analysis is the primary objective. Selective reaction monitorin g) techniques with a triple quadrupole mass spectrometer enabled sensitive and specific detection of IQ adducts, with detection limits approaching 1 a dduct in 10(9) unmodified bases using similar to 500 mug of DNA. The DNA ad ducts N-(2 ' -deoxyguanosin-8-yl)-2-amino-3-methylimidazo[4,5-f]quinoline a nd 5-(2 ' -deoxyguanosin-N-2-yl)-2-amino-3 -methylimidazo[4,5-f]quinoline w ere detected in pancreas tissue of a cynomolgus monkey sacrificed 24 h afte r a single administration of 10 mg/kg carcinogen. The LC/MS results were co nsistent with previously published P-32-postlabeling data (Turesky et al. C hem Res. Toxicol. 1996, 9, 403-408). Thus, capillary tandem LC/MS is a high ly sensitive technique, which can be used to screen for DNA adducts in vivo .