Determination of Taurine and Ethylparaben in Taurine Eye Drops by High-Precision Micellar Capillary Electrokinetic Chromatography

A method for simultaneous determination of taurine and ethylparaben in taurine eye drops by high-precision micellar capillary electrokinetic chromatography was established. 5.0 mL of taurine eye drops sample was made its volume up to 10 mL with water. The subsequent filtrate was obtained as sample solution for test affer mixing ultrasonically and filtrating through 0.22 μm microporous membrance. A quartz capillary column with isolation tank (75 μm of inner diameter, 65 cm of total length and 45 cm of effective length) was selected, and a mixture of borax and boric acid buffer (pH 9.0, 15 mmol·L^-1) containing 20 mmol·L^-1 sodium dodecylsulfate was used as separation buffer reagent. Electrophoretic separation was carried out at -15 kV of separation voltage and 210 nm of detection wavelength. As shown by the results, linear relationships between mass concentrations of taurine and ethylparaben and their peak areas were kept in the ranges of 5.02-40.80 g·L^-1 and 0.050-0.333 g·L^-1, with detection limits of 1.2 g·L^-1 and 0.005 g·L^-1, respectively. Intra-day precision (n=6) of mixed standard solution of taurine and ethylparaben were less than 2.0%, and inter-day precision (n=6) were less than 4.0%. Recovery test was made on substantial sample by standard addition method, and values of recovery were in the ranges of 93.9%-111% for taurine and 85.3%-107% for ethylparaben. This method has been applied for analysis of 3 batches of the taurine eye drops, and the determined values of taurine and ethylparaben were basically consistent with their labeled amounts.