Flow-Injection Spectrophotometric Determination of Phenols Using Analyte Oxidation in Manganese Dioxide or Lead Dioxide-Packed Reactors

Jana Dolejšová (dolejso@faf.cuni.cz), Miroslav Polášek, Rolf Karlíček

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

Summary

Flow-injection spectrophotometric method for determining »0.2 to 400 mmol · l^-1 of dihydroxyphenols (catechol, resorcinol, hydroquinone) and of trihydroxyphenols (pyrogallol, phloroglucinol, 1,2,4-hydroxyhydroquinone) using the analyte oxidation in manganese dioxide or lead dioxide-packed reactors (50 mm × 1.2 mm) with aqueous 10 mmol · l^-1 H₂SO₄ as carrier flow (0.6 ml min^-1) has been devised. Active and stable reactors packings were prepared by coating sintered glass particles (diam. 0.4 to 0.5 mm) successively with an epoxide glue and powdered MnO₂ or PbO₂. At the injected sample volume of 80 µl the relative standard deviation was 1.37 % (n = 10) when determining 1.0 mmol · l^-1 of catechol (»8.8 µg in 80 µl of the solution) in prepared solution of the pure substance and the sample throughput was 90 h^-1 (in manganese dioxide-packed reactors) or 60 h^-1 (in lead dioxide-packed reactors). The method has been applied to the analysis of phenols as bulk substances. The results were in good agreement with those of pharmacopoeial UV spectrophotometric determination.