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Abstract

The suitability of relatively slow (low absolute value of mobility) coanionic buffers in background electrolytes (BGEs) for indirect photometric detection of anions by capillary electrophoresis was investigated. As a model system, 2-(cyclohexylamino)ethanesulfonic acid (CHES) was used to buffer the indirect detection electrolyte of sodium chromate. CHES (pKa 9.55) is a zwitterionic molecule carrying a net negative charge depending on the pH (effective charge -0.5 at pH = pKa). Within its useful pH buffering range CHES acted as a competing probe coanion. System peaks were induced which had deleterious effects on the detection sensitivity of slow to medium mobility anions. The mobility of the system peak was determined by the effective mobility of CHES, both of which increased with increasing pH. The peaks of analytes that migrated near or on the system peak were distorted and lost all quantitative properties. Analytes that migrated after the system peak either were not detected or reversed their responses. Analytes that migrated well before the system peak were unaffected. Consequently, the suitability of slow coanionic buffers is limited either to (i) fast anions or, (ii) a pH range much below the pKa, where the buffering capacity is not optimal.

Item Type:	Article
Authors/Creators:	Doble, P and Macka, M and Haddad, PR
Keywords:	Background electrolyte • Capillary electrophoresis • Indirect detection • Fast anions
Journal or Publication Title:	Electrophoresis
ISSN:	0173-0835
DOI / ID Number:	https://doi.org/10.1002/elps.1150191235
Additional Information:	The definitive published version is available online at: http://interscience.wiley.com
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