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New isoelectric buffers for capillary electrophoresis: N-carboxymethylated polyethyleneimine as a macromolecular isoelectric buffer


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Macka, M and Johns, CA and Grosse, AC and Haddad, PR (2001) New isoelectric buffers for capillary electrophoresis: N-carboxymethylated polyethyleneimine as a macromolecular isoelectric buffer. Analyst, 126 (4). pp. 421-425. ISSN 0003-2654

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Isoelectric buffers are attractive for electrophoresis because of their low conductivity, and their compatibility with indirect photometric detection in capillary electrophoresis (CE) where they do not interfere with the detection by exhibiting competitive displacement of the UV-absorbing probe ion. N-carboxymethylated polyethyleneimine (CMPEI) was prepared by introducing a half molar equivalent of carboxylate groups onto a polyethyleneimine backbone. Its isoelectric point determined by conductometric titration and from the pH of its dilute aqueous solution is approx. 6.8, which allows isoelectric buffering at a lower pH compared to histidine (pI 7.7). Although the isoelectric point is somewhat diffuse, as expected for a polymeric compound, it exhibits a buffering capacity at a pI point of about twice that of histidine. Studies of electroosmotic flow (EOF) profile at various pH values in fused silica capillaries showed that CMPEI adsorbs onto the fused silica wall and reverses the EOF at pH < 6.5. CMPEI was applied as a buffer in an electrolyte containing 0.5 mM of the anionic dye tartrazine used as the probe for indirect detection of anions. The separation system exhibited a stable baseline, no system peaks, separation efficiencies of up to 195000 theoretical plates, and detection limits down to 0.2 µM or 2 amol of injected analyte.

Item Type: Article
Journal or Publication Title: Analyst
Page Range: pp. 421-425
ISSN: 0003-2654
Identification Number - DOI: 10.1039/b100608h
Additional Information:

Copyright © 2001 Royal Society of Chemistry

Date Deposited: 18 Nov 2008 04:17
Last Modified: 18 Nov 2014 03:52
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