[Determination of enantiomeric impurity of timolol maleate in bulk substances and eye drops].

OBJECTIVE: To determine the enantiomeric impurity contents of domestic timolol maleate in bulk drugs and eye drops.

METHODS: Enantiomer impurity of timolol was assayed by chiral high performance liquid chromatography. The chromatographic conditions were as follows:chiralcel OD chiral column (4.6 mm ×150 mm, 5μm), detection wavelength:297 nm, mobile phase:hexane-isopropanol-diethylamine (480:20:1), column temperature:25 ℃, flow rate:1.0 ml/min, sample injection volume:5 μl.

RESULTS: The resolution between R- and S-timolol was more than 4. The enantiomeric impurity contents were less than 0.67% on average in two batches of timolol maleate bulk drugs, and 0.31% on average in three batches of timolol maleate eye drops.

CONCLUSION: Enantiomeric impurity contents in each batch of products all meet European Pharmacopoeia criteria, which can be used as references in Chinese Pharmacopoeia criteria.