Extraction-free Spectrophotometric Determination of Pyrantel Pamoate in Pharmaceuticals

Abstract

The objective of this work was to develop and validate two direct, simple, highly sensitive, rapid and extraction-free spectrophotometric methods for the determination of Pyrantel pamoate (PYP) in commercial dosage forms. The methods are based on the formation of ion-pair complex between the base form of Pyrantel pamoate (PYL) and two sulphonthalein dyes, namely, phenol red (method A) and thymol blue (method B), followed by the measurement of absorbance at 430 nm and 420 nm respectively. Conformity to Beer’s law enabled the assay of drug in the range 0.02-0.5 and 0.05-0.8 µg ml –1 with apparent molar absorptivities of 5.11×10 5 and 2.55×10 5 l mol –1 cm –1 for method A and method B, respectively. The Sandell sensitivity values, limits of detection (LOD) and quantification (LOQ) values have also been reported for both the methods. The stoichiometry of the ion-pair complexes as evaluated by Job’s continuous variations method was 1:2 and the conditional stability constants (log K f ) were calculated to be 6.92 and 8.19 for method A and method B, respectively. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis; the relative error (%RE) was < 2.17% and the relative standard deviation (RSD) was < 1.77%. The methods were successfully applied to the determination of drug in tablets without interference by the common co-formulated substances. Statistical comparison of the results with the reference method showed good agreement and indicated that no significant difference in accuracy and precision.