Sensitive spectrophotometric determination of lamotrigine in bulk drug and pharmaceutical formulations using bromocresol green.

摘要

Two new, simple, rapid and reproducible spectrophotometric methods were developed for the detn. of lamotrigine (LMT) both in pure form and in its tablets. The first method (method A) is based on the formation of a colored ion-pair complex (1:1 drug/dye) of LMT with bromocresol green (BCG) at pH 5.02 ± 0.01 and extn. of the complex into dichloromethane followed by the measurement of the yellow ion-pair complex at 410 nm. In the second (method B), the drug-dye ion-pair complex was dissolved in ethanolic potassium hydroxide and the resulting base form of the dye was measured at 620 nm. Beer's law was obeyed in the concn. range of 1.5-15 μg/mL-1 and 0.5-5.0 μg/mL-1 for method A and method B, resp., and the corresponding molar absorptivity values are 1.6932 × 104 and 3.748 × 104 L/mol-1/cm-1. The Sandell sensitivity values are 0.0151 and 0.0068 μg/cm-2 for method A and method B, resp. The stoichiometry of the ion-pair complex formed between the dug and dye (1:1) was detd. by Job's continuous variations method and the stability const. of the complex was also calcd. The proposed methods were applied successfully for the detn. of drug in com. tablets. [on SciFinder(R)]