DETERMINATION OF A BIGUANIDE, METFORMIN, BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH PRECOLUMN FLUORESCENCE DERIVATIZATION

A sensitive method is described for determining a biguanide drug, metformin, by high-performance liquid chromatography with precolumn fluorescence derivatization. Metformin and phenylguanidine, as an internal standard, react with a novel fluorogenic reagent, desyl chloride, or benzoin to afford the corresponding fluorescent derivatives, which are separated by reversed-phase chromatography on a TSKgel ODS-120T column with linear-gradient elution. The applicability of the method to the determination of metformin in human serum is also demonstrated. The calibration curve of metformin was linear over the range of 0-100 nmol ml-1 in human serum. The detection limit (S/N=3) was 1.3 pmol per 20-mul injection volume.