Determination of soluble anions and cations from waters of pulp and paper mills with on-line coupled capillary electrophoresis

When the degree of closure of the paper machine wet end waters increases, w et end problems also become more difficult to control without specific and selective on-line measurements. The need to measure the concentrations of i ndividual compounds in order to explain wet end phenomena is growing. This study was performed to set up a CE system to a paper machine and to determi ne soluble inorganic and organic ions in different locations of pulp and pa per process waters with real time analyses by two on-line CE methods. A rec onstructed commercial CE apparatus was connected to a papermaking machine v ia an apparatus, which was a combined sampling and sample pretreatment inst rument, the role of which was to filter and dilute the samples before on-li ne determination by CE. The on-line procedures were optimized for simultane ous determination of anions as chloride, sulfate, oxalate, formate and acet ate and for determination of cations as potassium, calcium, sodium, magnesi um and traces of aluminium. The quantification was performed with external standard methods using the programs available in the commercial CE instrume nt. The concentrations of the ions were transferred by using a computerized transfer algorithm exporting the results from the analysis instrument to t he process control unit. The developed on-line procedures were tested three times in paper and paperboard mills for 1 month at a time. Correlations we re observed between the CE results and changes in the processes. (C) 2000 E lsevier Science B.V. All rights reserved.