Rapid and sensitive HPLC method for the simultaneous determination of dorzolamide hydrochloride and timolol maleate in eye drops with diode-array and UV detection

A rapid and sensitive HPLC method has been developed for the simultaneous determination of dorzolamide hydrochloride and timolol maleate. The drugs were monitored with a diode-array detector at two fixed wavelengths (lambda = 250.0 nm for dorzolamide hydrochloride and 300.0 nm for timolol maleate). Liquid chromatography was performed on a RP-YMC pack ODS A-132 C-18 (5 mum, 15 cm x 6.0 mm) column and the mobile phase consisted of an acetonitrile: phosphate buffer (pH 2.5): methanol (5:85: 10 v/v/v) mix and a flow rate of 1.2 ml (.) min(-1). The linearity of the method ranged between 4.0-45.0 mug (.) ml(-1) for dorzolamide hydrochloride and and 2.0-20.6 mug (.) ml(-1) for timolol maleate in binary mixture. The procedure was successfully applied to the determination of these compounds in pharmaceutical preparations and gave a high recovery, good accuracy and precision without any interference by the excipients.