Determination of the stability constant of the calcium binding ligand in black liquor (BL) by potentiometric titration

A1 Journal article (refereed)

Internal Authors/Editors

Publication Details

List of Authors: Kim Granholm, Tomasz Sokalski, Andrzej Lewenstam, Ari Ivaska
Publication year: 2016
Journal: Holzforschung
Volume number: 70
Issue number: 8
Start page: 733
End page: 738
eISSN: 1437-434X


The calcium binding ligand in black liquor (BL) has been investigated by the new CSSP (circumvention of slope and standard potential) method, which converts the potential of an ion-selective electrode to concentration or activity. The advantage of this approach is that the knowledge about the electrode standard potential and the slope of the calibration curve is not needed. Instead, two activities of calcium ion on the titration curve have to be estimated, for instance the starting activity before the titration begins and the activity at the end of the titration in presence of a large excess of the titrant. A solid-contact Ca2+-selective electrode was used to determine the stability constant of the Ca binding ligand in BL. In addition, the concentration of free and bound calcium was determined. The total Ca concentration obtained by the CSSP approach agreed well to that obtained by the ICP-OES technique. Other metal ions did not influence the determination if the BL concentration is around 3%.

Last updated on 2019-19-11 at 03:04