HPLC determination of the related substances in erdosteine

: An HPLC method was established for the determination of the related substance in erdosteine. Waters ODS-SunFire (250 mm x 4.6 mm ID, 5 microm) column was used, the mobile phase was composed of methanol-acetonitrile-0.01 mol x L(-1) citric acid (20:4:76, the pH value was adjusted by triethylamine to 2.5). The flow rate was 1 mL x min(-1). The detection wavelength was 254 nm. The related substances in the sample of erdosteine taken were calculated by self control with or without the response factor of impurity relative to that of erdosteine. Under the chromatographic condition developed, the impurities in erdosteine were isolated well. The detection limit was 0.2 microg x mL(-1) (signal/noise = 3) by principal component calculated. The method can be adopted to control the related substances in erdosteine.