On-line measurement of pulp water anions by capillary electrophoresis with fast sequential sampling and dynamic solvent feeding

This paper demonstrates the use of the first on-line capillary electrophoresis instrument with continuously flowing electrolyte solutions and sequentially applied sample introduction. The system was used in on-line determination of chloride, sulphate and carbonate concentrations of process waters at a pulp mill. The module constructed for on-line feedings of the solvents is described. Separations were performed in a pyromellitic acid-hexamethonium hydroxide-triethanol amine mixture at pH 7.7 with indirect-UV detection at 254 nm. Two standard mixtures were used to show the repeatability of the analysis and to estimate the accuracy of the on-line system. The analytes could be separated within 240 s. Sampling from a pulp machine could be accomplished on-line at 6 minute intervals. On-line tests gave a limit of detection and a limit of determination in the low mg/L range.