Non-aqueous and two-phase titrimetric assay of isoxsuprine hydrochloride in pharmaceuticals

Abstract

Based on the nitrogenous base or quaternary ammonium moiety in isoxsuprine hydrochloride (ISX), two highly accurate and selective titrimetric methods are proposed f or the determination of ISX in spiked human urine, injection and tablets. Non-aqueous titration (Method A) involves removal of protonated amine using mercuric acetate for enhanced basic nitrogen prior to titration with perchloric acid in an acetic acid medium using crystal violet as indicator. Two-phase titration (Method B) is based on ion association complex formation between sodium lauryl sulphate (SLS) and protonated amine of ISX at pH 2.5 in aqueous phase, end point being detected by change in dimethyl yellow color in chloroform layer. The methods are applicable over the concentration range 2.0–20.0 mg and 1.0–10.0 mg for method A and method B, respectively. Calculations are based on 1: 1 molar ratio, i.e., JSX: HClO4 for method A and ISX: SLS for method B, owing to the presence of one nitrogen atom. Method A is applicable to the determination of ISX in tablets whereas method B is applicable to spiked human urine, injection and tablets. The methods are validated statistically by comparing the results with those of the reference method by applying the Student’s t-test and F-test. The accuracy was further ascertained by recovery studies via standard addition technique.