SPECTROPHOTOMETRIC DETERMINATION OF REPAGLINIDE IN TABLETS BASED ON CHARGE-TRANSFER COMPLEXATION REACTION WITH CHLORANILIC ACID AND DICHLORO-DICYANO BENZOQUINONE

Two simple, accurate, precise, inexpensive, selective and sensitive spectrophotometric methods are described for the determination of repaglinide (RPG) in bulk drug and its tablets. The methods were based on the charge- transfer complex reaction between RPG in acetonitrile with p-chloranilic acid (CAA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in dioxane and subsequent formation of intensely colored radical anions of the reagents which were measured at 520 (CAA) or 590 nm (DDQ). Several experimental variables affecting the complex formation, stability of the colored species and sensitivity of the reaction were optimized. Under the optimized conditions, Beer's law was obeyed over the concentration ranges of 20-400 and 5-80 mu g ml(1) RPG for CAA and DDQ methods, respectively, and the corresponding correlation coefficients were 0.9995 and 0.9998. The apparent molar absorptivity values were 1.02x10(3) and 4.60x10(3) for CAA and DDQ methods, respectively, with corresponding Sandell sensitivity values of 0.4438 and 0.0984 mu g cm(-2). Limits of detection (LOD) were calculated to be 7.07 and 2.42 mu g ml(1) and the limits of quantification (LOQ) were 21.43 and 7.33 mu g ml(1) RPG, for CAA and DDQ methods, respectively. Validation results demonstrated that the inter day and infra day accuracy were up to 97.56%. The precision determined did not exceed 2.5% of RSD. The methods were successfully used for the determination of RPG in tablet form and the results were in good agreement with the label claims as shown by the recoveries which were in the range of 99.22-102.8% with standard deviation values <2%. The accuracy of the methods was confirmed by recovery studies via standard-addition procedure with excellent recovery 98.24-104.0 +/- 1.08-3.35.