UV spectrophotometric methods for simultaneous determination of ketorolac tromethamine and olopatadine hydrochloride: Application of multiple standard addition for assay of ophthalmic solution

Ophthalmic preparations that contain ketorolac tromethamine (KET) and olopatadine HCl (OLO) are used to relieve seasonal allergies and allergic conjunctivitis. Simultaneous quantification of KET and OLO was held by validated and simple spectrophotometric methods. KET was determined directly from the fundamental UV absorption spectra (at 323 nm), while OLO was determined after performing either dual wavelength or ratio derivative methods. The first method was based on measuring the absorbance difference (Delta A) between 243 and 291 nm, while the second depended on generating first derivative ratio spectra using 3.0 mu g/mL KET as a divisor and measuring OLO responses at 234 nm (minima). Multiple standard addition method was applied to enable the determination of OLO which is considered as the weakly absorbing species as well as the minor component in a challenging dosage form ratio (4:1). The linearity ranges of the developed methods were 3-12 mu g/mL and 4-40 mu g/mL for KET and OLO, respectively. Simultaneous determination of both drugs was successfully implemented to lab prepared eye drops that contain KET, OLO and benzalkonium chloride as an inactive ingredient. Greenness assessment indicates minimal impact on environment. The developed methods determined the cited drugs with % recovery +/- SD of 99.63 +/- 0.01 for KET, 100.90 +/- 0.02 and 100.31 +/- 0.01 for OLO using dual wavelength and first derivative ratio methods, respectively. Using F-test and t-test at confidence level %95 to compare between the results of the presented methods and a reported method show no significant difference which allows precise, accurate, rapid, and simple quantification of quality control samples that contain KET and OLO.