Development and Application of Ligand-Exchange Reaction Method for the Determination of Clonazepam

Purpose: This paper presents an improved kinetic-spectrophotometric procedure for determining clonazepam (CZP) in pharmaceutical formulations and human serum. Methods: The method is based on ligand-exchange reaction. The reaction was followed spectrophotometrically by measuring the rate of change of absorbance at 425 nm in ethanolic sodium hydroxide solution. Results: The optimum operating conditions for reagent concentrations and temperature were established. Linear calibration curve was obtained in the range of 0.32 - 4.10 μg mL-1. The optimized conditions yielded a theoretical detection limit of 0.24 μg mL-1 based on the 3.3So criterion, where S0 is standard deviation of the calibration line. The interference of certain drugs, foreign ions and amino acids on the reaction rate were studied in order to assess the selectivity of the method. Conclusion: The developed method is sensitive, accurate and reproducible and could be used for routine anlysis of clonazepam in pharmaceutical preparations and serum samples.