Development and validation of a capillary electrophoresis method for salicylic acid determination in pharmaceutical and cosmetic formulations

The current study reports on the development and validation of a new capillary electrophoresis (CE) method for the quantification of salicylic acid in pharmaceutical and cosmetic preparations. During preliminary analysis, capillary zone electrophoresis (CZE) using phosphate, borate, and mixed phosphate-borate buffers and micellar electrokinetic chromatography (MEKC), were evaluated; borate background electrolyte (BGE) led to better peak shape and was therefore selected for further method development. Separation was achieved in a fused-silica capillary (40 cm total length, 32 cm effective length, 50 µm i.d.) using an aqueous sodium borate BGE at pH 9.30, with an applied voltage of +20 kV, a temperature of 20 °C, hydrodynamic injection at the anodic end (50 mbar/1 sec.), and UV–DAD detection at 300 nm. The method was linear over 0.03-1.00 mg/mL (R² 0.994) calibration range. The limit of detection (LOD) was 0.01 mg/mL, and the limit of quantification (LOQ) was 0.03 mg/mL. Mean recoveries in spiked matrices were between 98.5-101.2%. Small deliberate variations of BGE concentration, pH, voltage, and temperature did not significantly affect responses, confirming robustness. The procedure is simple, solvent efficient, and suitable for routine quality control of cosmetic and pharmaceutical products containing salicylic acid.