Simultaneous determination of brinzolamide, timolol maleate and its oxidative degradation product using univariate and multivariate green spectrophotometric methods

Abstract

Spectrophotometric methods utilizing ratio-spectra were validated for simultaneous determination of Brinzolamide (BRZ) and Timolol maleate (TM) in the presence of the oxidative degradation product of TM (TM deg). TM deg interference was eliminated by dividing the zero-order absorption spectra of TM and BRZ by a concentration 20.00 μg/mL of TM deg. The binary mixture was then analyzed via Method A which determined TM using a ratio difference spectrophotometric approach, where amplitude difference (ΔPA) of the TM spectra at 275.5 nm and 250.0 nm were used, as BRZ (ΔPA) was zero at these wavelengths. Method B involved adjusting the first derivative of the ratio spectra of BRZ and TM in order to determine BRZ selectively. When applying Δλ = 8, scaling factor = 10 and the maximum obtained at 243.8 nm, TM showed no contribution. Method C, involved dividing the total spectrum of the ternary mixture by a double divisor; the sum of the spectra of TM and TM deg. The amplitude of the first derivative of the resulting ratio spectra was measured at 243.7 nm to determine BRZ. Additionally, two multivariate methods, Partial Least Squares and Artificial Neural Networks were applied for determination of BRZ, TM and TM deg. Both models successfully determined BRZ, TM and TM deg. These methods were applied to analyze BRZ and TM in pharmaceutical formulations without matrix interference. Finally, the environmental sustainability of the proposed methods was evaluated. Two methods; National Environmental Methods Index and Eco-Scale assessment metric systems were utilized and revealed greenness of proposed methods.