Novel Kinetic Spectrophotometric Method for Determination of Tiopronin [N-(2-Mercaptopropionyl)-Glycine]

Novel simple kinetic spectrophotometric method for the determination of tiopronin [N-(2mercaptopropionyl)-glycine, MPG] in pharmaceutical formulation has been developed and validated. The proposed method is based on the coupled redox-complexation reaction whose first step is reduction of Fe by MPG, while second one includes the complexation of Fe, resulted from preceding redox reaction, with 2,4,6-trypyridyl-s-triazine (TPTZ). The stable Fe(TPTZ)2 complex exhibits an absorption maximum at  = 593 nm. The initial rate and fixed time (at 3 min) methods were utilized for constructing the calibration graphs. The graphs were linear in concentration ranges from 1.0  10 to 1.0  10 mol L for both methods with limits of detection 1.3  10 mol L and 7.5  10 mol L for the initial rate and fixed time method, respectively. The proposed methods were successfully applied for the determination of MPG in its commercial pharmaceutical formulation.