Experimental Design Approach to Optimize HPLC Separation of Active Ingredients, Preservatives, and Colorants in Syrup Formulation.

Preservatives and colorants in pharmaceutical products may be highly toxic, especially for sensitive individuals, when they are used in excessive amounts. In this context, sensitive and non-labor-intensive analytical methods with short analysis time for simultaneous quantification of these additive substances in drugs can meet all requirements in quality control laboratories. The aim of the study was to develop a simultaneous HPLC method for the analysis of pseudoephedrine HCl and guaifenesin, along with preservatives, methyl paraben and propyl paraben, and colorants, ponceau 4R and sunset yellow, in a syrup sample. Optimum conditions of HPLC separation were determined by Box-Behnken experimental design. Four independent variables of the separation were pH (6.0, 6.5, and 7.0) and flow rate of the mobile phase (2.0, 2.2, and 2.4 mL/min) and mobile phase ratios for the first and second gradient elutions (75, 80, and 85% for Gradient 1 and 50, 55, and 60% for Gradient 2 in terms of phosphate buffer percent, respectively). The optimum conditions were found to be pH, 6.3; flow rate, 2.4 mL/min; and mobile phase ratios (phosphate buffer-acetonitrile) for Gradient 1 and 2, 85+15 (v/v) and 60+40 (v/v), respectively. Simultaneous analysis of all compounds was achieved by using this HPLC method with a short run time below 10 min. This simple, rapid, and validated method is convenient and applicable for routine analysis of pharmaceutical products having similar composition without the need for any extraction step.