Determination of chlorhexidine digluconate and polyhexamethylene biguanide in eye drops by capillary electrophoresis with contactless conductivity detection

Polyhexamethylene biguanide hydrochloride (PHMB-HCl) and chlorhexidine digluconate (CHG) are cationic disinfectants widely used in aqueous personal products such as eye drops, lotions and creams. The antiseptics belong to the biguanide group, which are cationic substances well known for their effective action against microbial infection. In this work, capillary electrophoresis combined with contactless conductivity detection was used to determinate these substances in ophthalmic solutions. Statistical analysis of the results showed satisfactory precision ranging from 3 to 6% in peak area. The detection limits were determined to be 4 μg/mL for PHMB and 0.4 μg/mL for CHG. It is also demonstrated that the high sensitivity allows the method to be used for in vitro perfusion studies with rabbit cornea.