Densitometric and videodensitometric TLC determination of timolol and betaxolol in ophthalmic solutions

Abstract

A new, accurate, rapid TLC method has been established for determination of timolol maleate (Timohexal 0.1%, Timoptic 0.25%) and betaxolol hydrochloride (Betoptic 0.5%) in ophthalmic solutions. The selectivity of the separation of these drugs has been investigated by TLC on silica gel 60F 254 , silanized C 8 silica gel, and aluminum oxide 60 F 254 plates with ascending and horizontal development. Suitable conditions for separation were use of silica gel with ethyl acetate-methanol-25% aqueous ammonia, 80 + 18 + 2 ( v/v ), as mobile phase. The substances were visualized by UV irradiation at λ = 254 nm or by spraying with suitable reagents. Detection and quantification of timolol maleate and betaxolol hydrochloride were performed densitometrically at λ = 300 nm and λ = 218 nm, respectively, and videodensitometrically at λ = 254 nm. Results from quantitative analysis were statistically assessed by use of the calibration procedure, a calibration equation, the correlation coefficient ( R 2 ), and relative stan...