The use of photogenerated iodine for the determination of isoniazid in solid dosage formulation

Abstract

A shot cut method for the determination of isoniazid in a solid dosage formulation (DF) has been developed. The method is based on isoniazid titration with a solution of photogenerated iodine obtained as a result of irradiation of an auxiliary solution containing potassium iodide, a mixture of sensitizers (sodium eosinate, fluorescein, auramine taken in a molar ratio of 1:1:1) and phosphate buffer solution (pH 7.5). Since the titrant content in the cell was controlled using the voltammetric method (amperometric titration with two polarized electrodes), the interaction of a physiologically active compound with the latter was accompanied by a decrease in the amount of titrant in the cell and, hence, in the current in amperometric circuit. Stabilization of the current in the circuit of the amperometric setup indicated the completeness of the reaction, and, therefore, provided estimation of the content of a physiologically active compound in the dosage formulation. Further irradiation of the solution and measurement of the generation time required to replenish the loss of titrant in the cell also made it possible to regulate the content of isoniazid in the preparation. The technique was tested on the samples of solid dosed formulations. It was shown that the components of the tablet mass (calcium stearate monohydrate, polysorbate, crospovidone and potato starch) do not affect the results of the determination of physiologically active compound provided that the analyzed form is obtained at room temperature. The determined content of isoniazid in a solid dosage formulation varies in the range of 286.0 – 296.0 mg and falls within the range recommended by the General Pharmacopoeia Monograph 1.4.2.0009.15 (285 – 315 mg), which indicates that the quality of the drug meets the GMP standards. The linear dependence of the analytical signal on the concentration of physiologically active compound is observed in the range of 161 – 1610 mg for the drug «Isoniazid. Tablets, 300 mg». The calculated detection limits and quantitative determination are 13.5 and 41.0 mg (both in terms of change in the current strength and in the time of titrant generation), respectively. The developed photochemical method for the determination of isoniazid in solid dosed formulation is easy to use, meets the requirements set out in the guidelines for validation of bioanalytical methods, and does not require expensive equipment. The method can be recommended for routine control of the DF quality indicators in any analytical laboratory.