Multivariate Optimization and Validation of a CE method for Simultaneous Analysis of Dorzolamide Hydrochloride and Timolol Maleate in Ophthalmic Solution

A fast, accurate, precise, and sensitive capillary electrophoretic method has been developed for simultaneous analysis of dorzolamide hydrochloride and timolol maleate in eye drops. Response-surface methodology with a central composite design was used for optimization of buffer pH, applied potential, and temperature. Capillary electrophoresis at 25??C with NaH₂PO₄ buffer (pH?6.00, 0.025?M), and an applied potential of 20?kV was found to be suitable, and under these optimum conditions, dorzolamide hydrochloride and timolol maleate were separated in approximately 3?min. This method was validated and successfully applied to a pharmaceutical preparation, ophthalmic solution, and the results were compared with those from a spectrophotometric method described in the literature.