Periodate-Based Spectrophotometric, Microwell-Pate, and Microfluidic Paper-Based Colorimetric Assays of Chlorpromazine Hydrochloride in Pharmaceutical Formulations
摘要
Simple, sensitive, and cost-effective methods were developed for the quantitative determination of chlorpromazine hydrochloride (CPZ), a representative phenothiazine derivative. Upon oxidation with periodate, CPZ yields a stable, orange‑red radical cation species (CPZ*) with a characteristic absorption maximum at 526 nm. The reaction conditions were systematically optimized to obtain maximum absorbance and improved stability of the oxidation product. Optimal reaction conditions were 6 mol L⁻¹ H₃PO₄, 1 mol L⁻¹ HClO₄, 1 mmol L⁻¹ KIO₄, and room temperature, while tracing the reaction within 180 s of mixing the reactants. CPZ* was monitored by conventional spectrophotometric (method a), microwell plate colorimetric (method b), and microfluidic paper-based analytical device (µ-PAD) assessment (method c). The µ-PADs were fabricated using a Xerox wax printer on Whatman grade‑1 chromatography paper, and quantification was performed using a desktop scanner and digital image analysis. Linear calibration ranges were obtained for 0.00–12.00 µg mL− 1 (spectrophotometric), 0.00–12.00 µg mL− 1 (vial colorimetric), and 0.00-0.50 µgCPZ/spot (µ-PAD colorimetric). The detection limits were 0.081 µg mL− 1 (spectrophotometric), 0.130 µg mL− 1 (green channel vial colorimetric), and µgCPZ/spot (green channel µ-PAD colorimetric) methods, respectively. The three developed methods (a-c) demonstrated excellent precision, accuracy, and selectivity, and were successfully applied to the assay of CPZ in pharmaceutical dosage forms (tablets and injections) without interference from common excipients under resource‑limited settings. Comparison with previously reported spectrophotometric and oxidative methods demonstrated that the present method offers superior simplicity and comparable analytical performance.
Graphical Abstract