Spectrophotometric Determination of Drugs Using Iodine As Analytical Reagent

Six drugs viz., Astemizole, Cisapride, Domperidone, Pantoprazole, Rabeprazole and Trazadone were tested for the formation of charge transfer complexes with Iodine. Each of these drugs turned the violet coloured i.e iodine , in CH2Cl2, to brown and exhibited a new band at 366nm in addition to the original band of iodine at 510nm due to anion of the reagent whose intensity increased with increase in the concentration of the drugs and formed a basis for quantitative determination of the drugs. The complexes were found to have 1:1 composition and have stability of the order 10 3 to 10 . The effect of the concentration reagent, polarity of solvent, interference of excipients have been studied and optimized. Dichloroethane (DCE) was found to be suitable solvent for the analysis. The methods have been validated in terms of ICH guidelines and applied to the quantification of pharmaceuticals. The variation of slopes of calibration plots and stability constants of the complexes are discussed in terms of structures of the drugs.