Optimization of ICP-MS Analysis for Studying Matrix Effects in Biological Fluids

A spectrophotometric method was developed for the precise estimation of clonidine hydrochloride (C-HCl) in pure form and pharmaceutical formulations. This method utilizes an ion-pair interaction with 1,2-naphthoquinone-4-sulphonic acid (NQS) in a basic medium (pH 13) at 55°C, producing a peach-colored solution with maximum absorbance at 475 nm. The method demonstrated linearity over 25-225 μg/mL with a molar absorptivity of 2162 L·mol-¹·cm-¹ (R² = 0.9986) and LOD and LOQ values of 6.28 and 19.02 μg/mL, respectively. The average recovery ranged from 96.4% to 101.4%. Kinetic studies indicated pseudo-firstorder kinetics, while thermodynamic analysis using Eyring and Arrhenius equations revealed the reaction to be endothermic and non-spontaneous. The method proved accurate and suitable for C-HCl analysis in pharmaceutical samples.