Development and Validation of a Gradient RP-HPLC Method Using a Risk-Based AQbD Framework for the Simultaneous Determination of Paracetamol, Phenylephrine Hydrochloride, Chlorpheniramine Maleate, and Oxolamine Citrate in an Effervescent Sachet Formul

A gradient RP-HPLC method was developed and validated for the simultaneous determination of paracetamol, phenylephrine hydrochloride, oxolamine citrate, and chlorpheniramine maleate in an effervescent sachet formulation. A structured, risk-based approach was applied during analytical procedure development to identify potential sources of variability and to select method parameters for further experimental evaluation. Based on the risk assessment, flow rate, column temperature, and detection wavelength were selected and evaluated by deliberate univariate variation around their nominal conditions. Separation was achieved on a reversed-phase C18 column using gradient elution with phosphate buffer (pH 4.5) and acetonitrile. Phenylephrine hydrochloride, oxolamine citrate, and chlorpheniramine maleate were monitored at 224 nm, whereas paracetamol was monitored at 300 nm. The method was validated according to ICH Q2(R2) for specificity, linearity, range, accuracy, precision, and robustness. Linearity was demonstrated over the investigated concentration ranges, with coefficients of determination (R²) greater than 0.999 for all analytes. Mean recoveries ranged from 98.24% to 101.01%, and the intermediate precision RSD% values were below 2.0%. No interference from the placebo was observed at the analyte retention times. Adequate chromatographic performance was maintained under the investigated deliberate variations in method parameters. The method was successfully applied to the simultaneous assay of the four active ingredients in the investigated commercial effervescent sachet formulation.