Spectrophotometric assay of diethylcarbamazine citrate in pharmaceuticals and spiked human urine by ion-pair reaction with Tropaeolin 000

A simple and rapid extractive spectrophotometric method is presented for the determination of diethylcarbamazine citrate (DEC) in bulk drug, dosage forms and spiked human urine. The method is based on the formation of orange colored ion-pair complex between the basic DEC and the acidic dye Tropaeolin 000 (TRN) in Clarks-Lubs buffer of pH 1.42. The formed complex was extracted by chloroform and the absorbance was measured at 490 nm. The effect of various experimental parameters on complex formation was investigated and optimized. Beer’s law is obeyed over the concentration range 2.0-70 μg mL^-1 (R =0.9995) with a molar absorptivity of 5.207×103 L mol^-1 cm^-1. The limits of detection (LOD) and quantification (LOQ) were calculated to be 0.15 and 0.46 μg mL^-1, respectively. The composition of the ion-pair was found to be 1:1 (DEC:TRN) by Job’s method of continuous variations. The relative standard deviation (%RSD) for intra-day and inter-day precision was less than 1.5% and the relative error (%RE) was better than 2.0%. The method was applied to the determination of DEC in tablets and syrup and the results agreed well with the label claim. The accuracy of the method was confirmed by recovery study via standard-addition procedure. In virtue of its high sensitivity, the method was applied to spiked human urine and an excellent percent recovery of 96.38±1.64 was obtained.