Extractive ion-pair spectrophotometric methods utilizing bromocresol green to estimate chlorpheniramine maleate in pharmaceutical formulations

Abstract Two accurate, sensitive, and cost-effective spectrophotometric methods were developed and validated for the quantitative determination of Chlorpheniramine Maleate (CPM). Method A is based on the formation of a yellow ion-pair complex between CPM and bromocresol green (BCG) in an acidic medium. The resulting complex is extracted into dichloromethane, and its absorbance is measured at 414 nm. Method B involves the dissociation of the yellow-colored CPM–BCG ion-pair complex in a basic medium, leading to the development of a blue color that gives a maximum absorbance at 618 nm. Beer’s law was found to be valid within the concentration ranges of 1.00–25.0 µg/mL for method A and 0.20–9.00 µg/mL for method B. The molar absorptivities were determined and found to be 1.76 × 10 4 and 4.47 × 10 4 L/(mol.cm) for methods A and B, respectively, with Sandell sensitivity values of 0.0222 and 0.0087 µg/cm². Detection and quantification limits were determined and found to be 0.2049 and 0.6210 µg/mL for method A, and 0.0199 and 0.0603 µg/mL for method B, respectively. The linearity was excellent with correlation coefficients of 0.9995 and 0.9997 for methods A and B. The developed methods were successfully employed to determine CPM in both its pure form and commercial pharmaceutical formulations. The methods were highly precise, with relative standard deviations between 0.24% and 1.85%, and highly accurate, with recovery percentages ranging from 98.14% to 100.8% when applied to pharmaceutical formulations. Statistical comparison with the official USP HPLC method showed no significant differences in accuracy or precision, making the developed methods ideal for routine quality control in resource-limited settings.