Detection and identification of benzo[a]pyrene diol epoxide adducts to DNA utilizing capillary electrophoresis-electrospray mass spectrometry.

Abstract

Capillary zone electrophoresis (CZE) coupled with negative ion electrospray mass spectrometry (ES-MS) is used for the detection and identification of adducts formed from the reaction of DNA with (+/-)-anti-7,8,9,10-tetrahydrobenzo[a]pyrene-7,8-diol 9,10-epoxide (BPDE),an active metabolite of benzo[a]pyrene (BaP). Results presented in this paper demonstrate low nanogram detection limits ( < 10 ng or < 15 pmol) for normal scan spectra and collision-induced dissociation spectra of the main nucleotide adduct formed from this reaction. (BPDE reacts predominantly with the exocyclic amino group of guanine.) Exploitation of selective reaction monitoring (SRM) produces detection limits in the low picogram range ( < 85 pg or < 130 fmol). The application of sample stacking significantly increases the concentration detection limit (to approximately 10(-8) M). Nucleotide adducts are negatively charged at most pHs and are therefore ideally suited to the stacking process used in this research. These techniques have been applied to the analysis of the adducts formed from the in vitro reaction of BPDE with DNA. In addition it is shown that CZE-ES-MS, combined with solid-phase sample cleanup, can detect adducts at levels of four adducts in 10(7) unmodified bases or less.