Abstract

Development of a spectrophotometricmethod for simultaneous determination of dorzolamide and timolol by partial least-squares and Hpoint standard addition method

Author(s): Masoud Shariati-Rad, Mohsen Irandoust, Maryam Karimi

Simultaneous determination of dorzolamide (DOR) and timolol (TIM) by partial least squares (PLS) calibration and H-point standard addition method (HPSAM) is proposed. Due to the spectral interferences, simultaneous determination of DOR and TIM by using classical spectrophotometric analytical methods is difficult. PLS calibration model was based on the recording spectra in the range of 200–350 nm for 24 different mixtures of DOR and TIM. Simplex lattice design with a lattice degree of 3 was used for design of mixtures. Leave one out cross-validation method was used to select the optimumnumber of factors in PLS. The PLS method was validated by using 11 external test samples. The root mean square error of prediction (RMSEP) for DOR and TIM were 0.397 and 0.583, respectively. Moreover, the proposed methods were successfully used for determination of DOR and TIM in eye drop. The results of application of H-point standard addition method showed that DOR and TIM can be determined simultaneously with concentration ratios of 4:1, 8:2, 10:2.5 in the mixed sample. The results of application of two methods to the real eye drop samples showed the success of two methods.