Assay of Pyrantel Pamoate Using Iron (III) Chloride and Three Complexing Agents by Spectrophotometry

Three rapid, simple, moderately sensitive and selective spectrophotometric methods are described for the determination of pyrantel pamoate (PYP) in bulk drug and in its pharmaceutical formulations. The methods are based on the reduction of ferric chloride by PYP in neutral medium and subsequent complexation of iron (II) with ferricyanide (method A), 1, 10-phenanthroline (method B) and 2, 2’-bipyridyl (method C). The absorbances of resulting colored products were measured at 750, 520 and 530 nm, respectively. Under the optimum conditions, Beer’s law enabled the determination of the drug in the concentration ranges 3.0-35, 1.0-30 and 2.0-35 μg mL-1 with apparent molar absorptivities of 1.38 × 104, 2.06 × 104 and 1.23 × 104 L mol-1 cm-1 for method A, method B and method C, respectively. The Sandell sensitivity values, limits of detection (LOD) and quantification (LOQ) values have also been reported for all methods. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis; the relative error (%RE) was ≤ 3.0 % and the relative standard deviation (RSD) was ≤ 1.98 %. The developed methods were successfully applied to the determination of drug in tablets and suspension without interference by the common excipients.