Simultaneous determination of gallic acid and resorcinol based on an oscillating chemical reaction by the analyte pulse perturbation technique

The potential of the analyte pulse perturbation technique for the resolution of mixtures in chemical oscillating reactions was evaluated. The approach was tested on the simultaneous determination of gallic acid and resorcinol through their perturbation effects on the copper(II)-catalysed reaction between hydrogen peroxide and sodium thiocyanate implemented in a continuous-flow stirred-tank reactor. The proposed method allows the direct simultaneous determination of these compounds at the μmol level with gallic acid/resorcinol ratios from 1:6 to 1:35, even in the presence of synergistic effects, with good precision (relative standard deviation) of 4.42 and 3.58%, respectively, and appreciable sample throughput (5 samples h−1). The proposed method is simple and flexible owing to a suitable manipulation of the experimental conditions — mainly the overall reactant flow-rate and temperature — the concentration ranges of gallic acid and especially resorcinol in the mixture could be changed according to practical requirements.