Development of a high-performance liquid chromatographic method for the determination of pyridoxine hydrochloride in shampoos

A high-performance liquid chromatography (HPLC) method was developed and validated for the quantitative determination of pyridoxine hydrochloride in shampoos. Chromatographic separation was achieved on a C18 column (250 × 4.6 mm; 5.0 µm). The mobile phase consisted of methanol and 0.015 M KH₂PO₄ buffer (pH 3.0), with gradient elution performed at a flow rate of 1 mL/min. Detection was performed at 290 nm with a total run time of 18 min. The diluent was a mixture of methanol and water (2:8, v/v) and the injection volume was 20 µL. The HPLC method was validated according to International Council for Harmonisation (ICH) and the AOAC INTERNATIONAL guidelines in terms of system repeatability, specificity, linearity, accuracy, precision, limit of detection (LOD), limit of quantification (LOQ), stability of standard solution, stability of test solution and robustness. The LOD and the LOQ were found to be 0.039 µg/mL and 0.156 µg/mL, respectively. The linear range was from the LOQ to 150% of the assay concentration (0.156 - 15.090 µg/mL). The results demonstrated that the method was suitable for the intended application. The validated method was successfully applied to the assay of pyridoxine hydrochloride in commercial shampoos marketed in Vietnam and provides a reliable tool for cosmetic quality control