Study of method validation criteria in a capillary electrophoresis method for the separation of non-steroidal anti-inflammatory drugs Original Research Article

The separation of three non-steroidal anti-inflammatory drugs (NSAIDs) by a capillary electrophoresis (CE) method was examined and validated. The method was first optimised using experimental designs (half-fraction factorial designs for five factors). The finally selected conditions consisted of a borate buffer with ionic strength 0.09 and pH 9.0, an applied voltage of 20 kV and an injection time of 10 s. The validation of the method showed good results for the selectivity, linearity, system repeatability and bias. The results obtained from peak areas, corrected peak areas and peak heights were compared. The calibration lines from peak areas and corrected peak areas were linear while those from peak heights curved. In some concentration ranges the data were heteroscedastic. The ordinary least squares (OLS) and weighted least squares (WLS) regressions were used and compared in a low-concentration range of the drug solution. Half-fraction factorial designs were also applied to test the robustness of the method. The validation of the method approves the assay for the quantitative determination of the examined substances, occurring alone or in mixtures.