SIMULTANEOUS DETERMINATION OF 7-METHYLGUANINE AND O-6-METHYLGUANINE IN DNA BY LIQUID-CHROMATOGRAPHY WITH POSTCOLUMN FLUORESCENCE DERIVATIZATION USING 3,4-DIMETHOXYPHENYLGLYOXAL

3,4-Dimethoxyphenylglyoxal was found to react sensitively and selectiv ely with guanine-containing compounds to yield their fluorescent deriv atives. This reaction and postcolumn fluorescence derivatization liqui d chromatography were used to determine the production of 7-methylguan ine and O-6-methylguanine in DNA after alkylation with N-methyl-N-nitr osourea. In this method, nucleic acid bases produced by acid hydrolysi s were separated on a reversed phase column (TSK-gel ODS-120T) and sub jected to postcolumn derivatization involving demethylation followed b y fluorescence reaction with 3,4-dimethoxyphenylglyoxal. The detection limits (S/N =3) for 7-methylguanine and O-6-methylguanine were 6.7 an d 0.7 pmol respectively in a 20 mu l injection volume. (C) 1998 Elsevi er Science B.V.