DETERMINATION OF 9,10-DIHYDROXYANTHRACENE AND ANTHRAQUINONE IN KRAFT PULPING LIQUORS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A simple chromatographic method was developed to determine the amount of anthraquinone (AQ) and its reduced form, the disodium salt of 9,10- dihydroxyanthracene (Na(2)AQ), in white pulping liquors. The method is based on the different solubilities of AQ (insoluble) and Na(2)AQ (so luble) in aqueous medium. Prior to analysis, samples (containing AQ Na(2)AQ) are filtered to remove the insoluble quinone (AQ) and oxidize d with hydrogen peroxide. The resulting oxidized material, which corre sponds to the initial amount of Na,AQ present in the sample, is dissol ved in N,N-dimethylformamide (DMF) and this final solution is analysed for AQ by high-performance liquid chromatography. The basic operating conditions are as follows: detection wavelength, 254 nm; flow-rate, 1 .5 ml min(-1); temperature, 40 degrees C; eluent, methanol-water (82:1 8, v/v); and volume of sample injected, 10 mu l. The method is suitabl e for the determination of quinonoid compounds in the 5-2500 mu g ml(- 1) range in Kraft pulping liquor and the limit of detection is 0.5 mu g ml(-1).