Use of 2-mercaptopyridine for the determination of alkylating agents in complex matrices: application to dimethyl sulfate

A rapid and sensitive method for the determination of alkylating agents in complex reaction mixtures was developed and characterized. Analyses are based on the alkylation of 2-mercaptopyridine by the analyte; the derivative is separated by RP-HPLC and measured by fluorescence detection. When applied to the determination of dimethyl sulfate, the method is linear over four orders of magnitude: 0.01–10 μg mL−1. By using recrystallized 2-mercaptopyridine, quantitation limits of 10 ng mL−1 can be achieved. Precision of the assay is 2% R.S.D. in the 1–10 μg mL−1 range and about 15% R.S.D. at 10 ng mL−1. Studies on the pH dependence of the derivatization reaction were key to minimizing interference from the dimethyl sulfate degradation product, monomethyl sulfate, in quenched reaction samples.