Sensitive and selective extraction free ion-pair complexometric determination of domperidone in pharmaceuticals and in spiked human urine

Abstract

Domperidone (DOM) is a drug used as an antiemetic and to control gastrointestinal effects of dopaminergic drugs in the management of perkinsonism. Two simple, rapid, sensitive and selective extraction free spectrophotometric methods have been developed for the assay of DOM in pure drug, in pharmaceuticals and in spiked human urine sample. The methods are based on the formation of yellow ion-pair complexes between DOM and two sulphonphthalein dyes viz., thymol blue (method A) and bromothymol blue (method B) in acetone and dichloromethane medium. The complexes showed absorption maxima at 390 nm and 410 nm in method A and method B, respectively. Reaction conditions were optimized to obtain the maximum color intensity. The absorbance was found to increase linearly with increase in concentration of DOM, which was corroborated by the calculated correlation values of 0.9991 in method A and 0.9986 in method B. The systems obeyed Beer's law over the concentration range of 1.25 - 20 μg mL-1 in both the methods. The molar absorptivity values are calculated to be 1.53 × 104 and 2.06 × 104 L mol-1 cm-1 for method A and method B, respectively and the corresponding Sandell sensitivity values are 0.028 and 0.021 μg cm-2. The composition of the ion-pairs was found to be 1 : 1 by Job's method and the conditional stability constant (Kf) of the complexes have been calculated. The proposed methods were applied successfully to the determination of DOM in tablets as well as in spiked urine sample with good accuracy and precision.