HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ELECTROSPRAY MASS-SPECTROMETRYFOR THE ANALYSIS OF MODIFIED BASES IN DNA - 7-(2-HYDROXYETHYL)GUANINE, THE MAJOR ETHYLENE-OXIDE DNA ADDUCT

A method was developed for the analysis of 7-(2-hydroxyethyl)guanine ( 7HEG), the major DNA adduct formed after exposure to ethylene oxide (E O). The method is based on DNA neutral thermal hydrolysis, adduct micr oconcentration, and final characterization and quantification by HPLC coupled to single-ion monitoring electrospray mass spectrometry (HPLC/ SIR-ESMS). The method was found to be selective, sensitive, and easy t o handle with no need for enzymatic digestion or previous sample deriv atization. Detection limit was found to be close to 1 fmol of adduct i njected (10(-10) M), thus allowing the detection of approximately thre e modified bases on 10(8) intact nucleotides in blood sample analysis. Quantification results are shown for 7HEG after calf thymus DNA and b lood exposure to various doses of EO, in both cases obtaining clear do se-response relationships.