Electrospray mass spectrometry (ES-MS) is a powerful tool for analysis of carcinogen-adducted DNA. In this study, we developed a quantitative isotope dilution method for analysis of N-(deoxyguanosine-8-yl)-4-aminobiphenyl (dG-C8-4-ABP), the principal nucleoside adduct derived from enzymatic hydrolysis of 4-aminobiphenyl (4-ABP)-modified DNA. The method used column switching valves to perform on-line sample concentration and cleanup, which permitted direct analysis of enzymatic DNA hydrolysates using narrow-bore liquid chromatography (LC). ES-MS detection was performed using a single...

Electrospray mass spectrometry (ES-MS) is a powerful tool for analysis of carcinogen-adducted DNA. In this study, we developed a quantitative isotope dilution method for analysis of N-(deoxyguanosine-8-yl)-4-aminobiphenyl (dG-C8-4-ABP), the principal nucleoside adduct derived from enzymatic hydrolysis of 4-aminobiphenyl (4-ABP)-modified DNA. The method used column switching valves to perform on-line sample concentration and cleanup, which permitted direct analysis of enzymatic DNA hydrolysates using narrow-bore liquid chromatography (LC). ES-MS detection was performed using a single quadrupole instrument by monitoring M+H⁺ and two fragment ions characteristic for dG-C8-4-ABP, along with M+H⁺ and a fragment ion for the deuterated internal standard. The detection limit for dG-C8-4-ABP in DNA hydrolysates was ~10 pg on-column, equivalent to 0.7 dG-C8-4-ABP adducts in 10⁷ normal nucleotides for a sample containing 100 μg DNA. The method was applied to the analysis of calf thymus DNA modified in vitro through reaction with N-hydroxy-4-ABP and of hepatic DNA isolated from mice treated in vivo with two dose levels of 4-ABP.