Capillary zone electrophoresis for simultaneous determination of seven nonsteroidal anti-inflammatory drugs in pharmaceuticals

A simple capillary zone electrophoresis (CZE) method has been developed for analyzing seven nonsteroidal anti-inflammatory drugs (NSAIDs)—sulindac (SU), ketoprofen (KE), indomethacin (IN), piroxicam (PI), nimesulide (NI), ibuprofen (IB), and naproxen (NA). The separation was run using borate buffer (60 mmol L^–1, pH 8.5) containing 13% (v/v) methanol at 20 kV, and detected at 200 nm. Several conditions were studied, including concentration and pH of borate buffer, methanol percentage, and separation voltage. In method validation, the calibration plots were linear over the range 40.0–500.0 mol L^–1. In intra-day and inter-day analysis, relative standard deviations (RSD) and relative errors (RE) were all less than 5%. The limits of detection were 10 mol L^–1 for SU, IN, PI, and 20 mol L^–1 for KE, NI, IB, NA (S/N = 3, sampling 6 s by pressure). All recoveries were greater than 95%. This method was applied to the quality control of six NSAIDs in pharmaceuticals using NI as internal standard (IS). The assay results were within the labeled amount required by USP 25.