Abstract
Summary Two simple and sensitive spectrophotometric methods are described for the assay of trimebutine. The first method is based on the interaction of the basic drug in 1,2 dichloroethane with bromocresol green (BCG); bromophenol blue (BPB) and bromothymol blue (BTB) in the same solvent to produce a stable yellow ion-pair complexes , which absorbed at 410,406 and 405nm, respectively. The second method is based upon the interaction of the basic drug with iodine in 1,2 dichloroethane. The yellow colour formed due to the formation of charge-transfer complex showed two maxima absorbed at 292 and 362 nm. Beer's law obeyed for both methods and the relative standard deviations were found to be less than 1 %. The two methods can be applied to the analysis of tablets, with no evidence of interference from excipients. A more detailed investigation on the complex was made to its composition, association constant and free energy change.