Determination of lignin content in kraft black liquors by capillary zone electrophoresis (CZE)

Capillary zone electrophoresis (CZE) in an alkaline glycine buffer is suggested for the quantification of lignin content in black liquors (BL). The method was first tested by an external calibration with LignoBoost lignins. Then, the lignin content in BL was determined by means of a multivariate calibration with the application of a standard normal variate filter and partial least squares approach based on five principal components. The results are in agreement with those obtained by sulfuric acid lignin precipitation combined with ultraviolet measurement of the lignin in solution. The advantage of the CZE method is its independence from the knowledge of the exact absorptivity coefficient, which is needed for direct spectrophotometric lignin determination. Moreover, interfering substances and degradation products could be recognized and excluded from lignin determination; thus, the selectivity was increased significantly.