Stability indicating HPTLC determination of timolol maleate as bulk drug and in pharmaceutical preparations

Timolol was the first beta blocker to be used as an anti-glaucoma agent and to date remains as the standard because none of the newer beta blockers were found to be more effective. The high performance thin layer chromatographic method of analysis of timolol maleate is reported. The mobile phase selected was ethyl acetate-methanol-isopropyl alcohol-ammonia (25%) (80:20:2:1, v/v/v/v). The calibration curve of the drug was linear in the range of 100-600 ng. The spectrodensitometric analysis was carried out at 294 nm. The mean (+/- RSD) values of slope, correlation coefficient and intercept were 2487.3 ( +/- 0.9), 0.996 ( +/- 0.081) and 90463 (+/- 1.1), respectively. The system precision and the method precision were excellent with an RSD of 2.8 and 1.004, respectively. The limits of detection and quantitation were 10 and 40 ng, respectively. The mean percent recovery was found to be 98.6. Timolol maleate was degraded by exposing the drug to heat, acid and base. The degraded products were found to be well separated from the pure drug with significantly different R-f values suggesting a stability indicating analysis method for quantification of timolol maleate in pharmaceutical preparations and as bulk drug. The method was utilized to analyze timolol maleate from conventional eye drops and novel sustained release solid polymeric ocular inserts and oral preparations. The reported method is simple, selective, precise, accurate, time saving and economic as compared to reported HPLC methods. (C) 2000 Elsevier Science B.V. All rights reserved.