Simultaneous Analysis of Isoniazid and Its Impurities by CZE

Abstract

An alternative methodology for simultaneous determination of isoniazid, isonicotinic acid, 4-cyanopyridine, ethyl isonicotinate and isonicotinamide by capillary zone electrophoresis, within an analysis time of 11 min, is proposed. An electrolyte composed by 50 mmol L⁻¹ of acetic acid/sodium acetate buffer and 12.5 mmol L⁻¹ of Cu²⁺, an analyte dilution in 1 mmol L⁻¹ of Brij 35 and 12.5 mmol L⁻¹ of Cu²⁺ and +20 kV voltage were optimized. After evaluating some figures of merit, such as linearity, precision, recovery and quantification limit, the method was successfully applied to the isoniazid analysis in tablets. The contents found were 99.3 mg of isoniazid and 0.3 mg of isonicotinic acid, corresponding to 0.3 % of impurity regarding the content of the active ingredient in the pharmaceutical formulation.