Flow Injection Analysis of Hydroquinone, Pyrocatechol, Resorcinol, and Pyrogallol with Amperometric Detector

Abstract

A flow injection method was developed for the determination of hydroquinone, pyrocatechol, resorcinol, and pyrogallol by utilizing the redox reaction with iodate ion. Mixed solution of sulfuric acid (1 mol·dm^-3) and potassium bromide (0.42 mol·dm^-3), and potassium iodate solution (10^-4 or 4×10⁵ moli·dm^-3) were pumped at a rate of 0.35 cm³min^-1, and pure water at a rate of 1.14 cm³min^-1. The decrease of iodate ion concentration, resulted from the redox reaction with the sample, was monitored by measuring its reduction current with a platinum wire (0.5 mm o. d., 20 mm long) electrode held at +O.65 V (vs. a silver tubing) and a silver tubing (1.2 mm i. d., 20 mm long) electrode. Linear relations were found between the sample concentrations and the peak heights when 20 μl of the sample was injected. With the proposed method, hydroquinone (5×10^-5-10^-5 mol·dm^-5), pyrocatechol (5×10^-5-10^-3 mol·dm^-3), pyrogallol (2×10^-5-5 x 10^-4 mol·dm^-3), and resorcinol (4×10^-6-2 x 10^-4 mol·dm^-3) were determined with relative errors of less than 2.7, O.9, 0.8 and 3.6%, and coefficients of variation of less than O.7, 1.5, 1.2 and 0.7% respectively. It was possible to determine 24 samples per hour.