Development and validation of a capillary zone electrophoresis method for the determination of benzalkonium chlorides in ophthalmic solutions

A systematic investigation of optimal conditions for determining the benzalkonium chlorides in ophthalmic products by capillary zone electrophoresis (CZE) was presents. The most effective separation conditions was 40 mM phosphate buffer with 40% acetonitrile at pH 4.0, and the sample hydrodynamic injection of up to 10 s at 2 p.s.i. (1 p.s.i.=6892.86 Pa) (approximately 35.15 nl), and an applied voltage of 15 kV. The reproducibility of the migration time and quantitative analysis can be improved by using internal standard, triethylbenzylammonium chloride, giving the relative standard deviation less than 0.2% for the relative migration times, and 5.0-7.8% for the relative peak areas. A good linearity of CZE analysis was obtained in the range of 1.0-20 μg/ml with r² values of above 0.99. The established HPLC with UV-Vis detection was applied to evaluate the CZE method, and compatible results were obtained by using CZE with much shorter analysis time and a small quantity of solvents consumed.