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In-line application of electric field in capillary separation systems Part I: Joule heating, pH and conductivity
Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
Early Development, Pharmaceutical and Analytical Research & Development, AstraZeneca, Sweden.
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2008 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 75, no 1, 83-90 p.Article in journal (Refereed) Published
Abstract [en]

This study concerns the technique electric field-assisted capillary liquid chromatography. In this technique, an electric field is applied over the separation capillary in order to provide an additional selectivity. In this technique, the electric field is applied in-line in the separation capillary and here the electric current is the factor limiting the magnitude of applied electric field. The influence of Joule heating and other factors on the current in such systems has been investigated.

The temperature in the capillary was first measured within a standard CE set-up, as function of effect per unit of length. Then the same cooling system was applied to an in-line set-up, to replicate the conditions between the two systems, and thus the temperature. Thus Joule heating effects could then be calculated within the in-line system. It was found that for systems applying an electric field in line, the direct influence from Joule heating was only relatively small.

The pH in the capillary was measured in the in-line set-up using cresol red/TRIS solutions as pH probe. Significant changes in pH were observed and the results suggested that electrolysis of water is the dominant electrode reaction in the in-line system. In summary, the observed conductivity change in in-line systems was found to be mainly due to the pH change by hydrolysis of water, but primarily not due the temperature change in the capillary column.

Place, publisher, year, edition, pages
2008. Vol. 75, no 1, 83-90 p.
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kau:diva-1913DOI: 10.1016/j.talanta.2007.10.032OAI: oai:DiVA.org:kau-1913DiVA: diva2:5008
Available from: 2007-10-08 Created: 2007-10-08 Last updated: 2013-11-18Bibliographically approved
In thesis
1. In-line application of electric fields in capillary separation systems
Open this publication in new window or tab >>In-line application of electric fields in capillary separation systems
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The magnitude of an electric field possible to apply in a capillary separation system is limited, because a high electric field causes a too high current through the capillary. Application of the electric field in-line will give an increased conductivity in the column, further increasing the risk of too high currents. The conductivity changes were found to result from an overall increase in ionic strength within the electric field. The increase in ionic strength is caused by the increase in mobile phase ions with electrophoretic velocity against the flow, together with OH- or H3O+ ions (depending on polarity) formed at the inlet electrode. Further it was found that the use of a pressurized reservoir or splitting of the flow at the inlet electrode could significantly limit the conductivity changes and thereby the maximum applicable electric field strengths could be increased.

Place, publisher, year, edition, pages
Fakulteten för teknik- och naturvetenskap, 2006
Series
Karlstad University Studies, ISSN 1403-8099 ; 2006:55
Keyword
capillary separation, conductivity, in-line, electric field assisted liquid chromatography
National Category
Analytical Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kau:diva-1197 (URN)91-7063-086-0 (ISBN)
Public defence
2006-12-15, 9C203, Karlstad University, Karlstad, 10:15
Opponent
Supervisors
Available from: 2007-10-08 Created: 2007-10-08

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