Determination of Dihydroxyphenols by Flow Injection Analysis (fia) with Chemiluminescence Detection

Jana Dolejšová, Miroslav Polášek, Petr Solich, Rolf Karlíček

Department of Analytical Chemistry, Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Czech Republic

Summary

Flow injection method with chemiluminescence detection has been devised for determining ≈ 2--8 µmol.l^-1 of dihydroxyphenols (catechol, resorcinol, hydroquinone). The samples are made 60 mmol.l^-1 in aqueous sodium hexametaphosphate (enhancer of the chemiluminescence) and injected (for 5 s) into a reagent stream (flow rate 0.91 ml.min^-1) of 0.25 mol.l^-1 H₂SO₄ containing 0.5 mmol.l^-1 KMnO₄ (for catechol) or 0.3 mmol.l^-1 KMnO₄ (for the other phenols) as oxidant. The injected sample volume was 200 µl. The relative standard deviation (RSD) values of the peak heights ranged betwen 1.74 % (resorcinol) and 0.82 % (hydroquinone), n = 10, when injected ≈ 5 µmol.l^-1 calibration solutions of the phenols. The method has been applied to the analysis of phenols as bulk substances. The sample throughput was 171 sample.h^-1. The results were in good agreement with those of VIS spectrophotometric (Emerson reaction) determination, as evaluated by the Student t-test.