Spectrophotometric Study of Isoniazid by Using 1,2-Naphthoquinone-4-Sulfonic Acid Sodium as the Chemical Derivative Chromogenic Reagent

A new method for the determination of isoniazid by using 1,2-naphthoquinone-4-sulfonic sodium as the chemical derivative chromogenic reagent is established. The method is based on a condensation reaction to measure the pink compound produced by the reaction of isoniazid with 1,2-naphthoquinone-4-sulfonic sodium in pH 13.00 buffer solution. The stoichiometric ratio of the compound is 1:1, and its maximum absorption wavelength is at 460 nm, ϵ = 1.18 × 104 L·mol−1 cm−1. Beer's law is perfectly obeyed in the range of 0.50˜30 μg.mL−1 of isoniazid. The linear regression equation is A = 0.0185 + 0.11056C (mol.L−1), with 0.9994 of a linear regression correlation. The detection limit is 0.40 μg.mL−1, RSD is 0.48%, and average recovery is over 99.3%. This paper further optimizes the determination of isoniazid compared to the previous methods, and the kinetic property and reaction mechanism are studied intensively. This proposed method has been successfully applied to the determination of isoniazid in tablets of isoniazid with satisfactory results.