QUANTITATIVE-DETERMINATION OF 8-HYDROXYGUANINE AND GUANINE BY ISOTOPE-DILUTION MASS-SPECTROMETRY

8-[4,5,6,8-C-13(4)]Hydroxyguanine and [4,5,6-C-13(3)]guanine were prepared by total synthesis. The labeled compounds were used as internal standards in a gas-liquid chromatographic-mass spectrometric method for quantitative determination of 8-hydroxyguanine and guanine in DNA. The approach used made it possible to directly determine the ratio between 8-hydroxyguanine and guanine, expressed as the number of molecules of 8-hydroxyguanine per 10(5) molecules of guanine, in the sample of DNA analyzed. A method for trimethylsilylation of 8-hydroxyguanine and guanine at room temperature was developed. Use of this method for derivatization gave levels of 8-hydroxyguanine in calf thymus DNA which were lower than those recently found by gas chromatography-mass spectrometry but similar to those determined by high-performance liquid chromatography with electrochemical detection. (C) 1995 Academic Press, Inc.