Spectrophotometric Assay of Diethylcarbamazine Citrate in Pharmaceuticals and Human Urine via Ion-Pair Reaction Using Methyl Orange Dye

Abstract

Two simple and moderately selective spectrophotometric methods are described for the determination of Diethylcarbamazine Citrate (DEC) in bulk drug, dosage forms and spiked human urine. The first method (method A) is based on the formation of yellow colored ion-pair complex between DEC and Methyl Orange (MO) dye, at pH 4.95 ± 0.05, which was extracted into chloroform and measured at 420 nm. The second method (method B) involved the breaking of yellow ion-pair complex in acid medium followed by the measurement of the free dye at 520 nm. Experimental parameters influencing the formation and extraction of the ion-pair complex in method A and breaking of the complex in method B were scrupulously examined and optimized. Beer's law is obeyed over the concentration ranges of 10-90 and 5-100 µg mL -1 DEC with corresponding molar absorptivity values of 2.90×10 3 and 3.54×10 3 L mol -1 cm -1 for method A and method B, respectively. The Sandell's sensitivity values were 0.1351 and 0.1106 µg cm -2 for method A and method B, respectively. The Limits of Detection (LOD) and Quantification (LOQ) were calculated to be 0.36 and 1.09 µg mL -1 (method A) and 0.34 and 1.02 µg mL -1 (method B). The composition of drug-dye ion-pair complex used in method A was found to be 1:1 by Job's method of continuous variations. The proposed methods were validated for robustness, ruggedness and selectivity, and applied to the determination of DEC in tablet, syrup formulations and spiked human urine samples. The results demonstrated that the proposed methods are as accurate and precise as the reference method. The accuracy of the methods was further ascertained by recovery study via standard-addition method. MaterialsPure Diethylcarbamazine Citrate (DEC), certified to be 99.86% pure was procured from Inga Laboratories Pvt. Ltd., Mumbai, India and used as received. Banocide forte tablets (Glaxo SmithKline Pharma. Ltd., Nashik, India) containing 50 and 100 mg DEC per tablet, Banocide syrup (Glaxo SmithKline Pharma. Ltd., Bangalore, India) containing 120 mg DEC per 5 mL and Decet tablets containing 150 mg DEC per tablet (from RND Laboratories Pvt. Ltd., India) were purchased from local commercial sources. Reagents and chemicalsAll reagents and solvents used were of analytical reagent grade. Double distilled water was used to prepare aqueous solutions wherever required. Standard stock solutionA stock standard solution (100 µg mL -1 DEC) was prepared by dissolving accurately weighed 10 mg of pure DEC in water and diluted to volume with the same solvent in a 100 mL calibrated flask. General Procedures Method ATo a set of 125 mL separating funnels, appropriate aliquots (1.0-9.0 mL) of the standard working solution (100 µg mL -1 ), were transferred to obtain concentrations in the range of 10-90 µg mL -1 DEC, and the solutions were diluted to 10 mL with water. To each separating flask were added 2 mL of buffer solution of pH 4.95, followed by 6 mL of 0.05% MO solution and made up to 20 mL with water and mixed well. A 10 mL portion (accurately mea...