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Problematics and stability of on‐line pH measurements in anaerobic environments: The jellied combined electrode
Author(s) -
Monzambe Kuma M.,
Naveau Henry P.,
Nyns EdmondJacques,
Bogaert Nicolas,
Bühler Hans
Publication year - 1988
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260310705
Subject(s) - electrode , clogging , diaphragm (acoustics) , chemistry , porosity , analytical chemistry (journal) , chromatography , electrical engineering , archaeology , organic chemistry , loudspeaker , history , engineering
Discrepancies of one pH unit and more have been observed after a few days, between continuous on‐line in situ pH measurements and instant off‐line pH measurements during anaerobic digestion of an agroindustrial wastewater. Concomitantly, the electrical resistance across the porous diaphragm of the on‐line electrode increased, and a black clogging developed on its diaphragm. Measurements of the relative liquid junction potential in KCl or Na 2 S solutions excluded that high concentrations of ions such as, K + , Na + , Cl − , HS − , or S 2− were the major cause of the drifts in pH values. It has been possible to limit the rapid increase of the liquid junction potential and the black clogging formation on the porous diaphragm either by acidification and/or by overpressurization of the electrode‐filling liquid. Continuous on‐line in situ pH values consistent with instant off‐line pH values over long periods of time have been obtained with a newly designed pH sensor in which a special jellied electrode filling replaced the porous diaphragm.