Improved Methods for Measuring Residual Effective Alkali in Kraft Black Liquors - Part 1: Absolute Measurement by Capillary Electrophoresis, 2007 Engineering, Pulping & Environmental Conference

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A rapid and selective method has been developed for the simultaneous determination of hydroxide, sulphide, thiosulphate, sulphite, and oxalate in kraft liquors by capillary electrophoresis with direct UV-detection. Separations are completed in less than three minutes using a carrier electrolyte consisting of sodium sulphate and tetradecyltrimethyl ammonium hydroxide. The method exhibits a wide linear range, thus allowing for the analysis of disparate levels of anions in a single analysis. The hydroxide result obtained by the method is equivalent to the effective alkalinity in the sample, while the sulphide result corresponds to the free sulphide content of the liquor. Results obtained by the current method were found to agree well with those obtained by standard addition, standard titration, and ion chromatography analysis. For the determination of hydroxide in black liquors, a comparison of the CE results was made with the SCAN N 33:94 Standard Method, which includes a correction factor to account for the co-titration of organic acids. The new CE method, which does not suffer from such interference, provides a direct means of measuring hydroxide in black liquor, and thus can be used to accurately quantify residual effective alkali