UV detection in capillary zone electrophoresis : peaks or dips - that is the question

J.L. Beckers

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Applying capillary zone electrophoresis with UV detection, both UV-absorbing and UV-transparent components can be present in electropherograms as neg. peaks (dips) or as pos. peaks. Starting from Kohlrausch's regulation function, derived for fully ionized monovalent ionic constituents and under the assumption that the molar absorptivities of the UV-absorbing components are identical, eight different cases can be distinguished and in several cases components can occur both as peaks or as dips depending on their mobilities and those of the co-ions of the system. Applying background electrolytes contg. two co-ions, system peaks are present, with a mobility that is between the mobilities of the two co-ions and detd. by the concn. ratio of these two co-ions. In the background electrolytes studied, contg. the co-ions potassium and histidine, UV-transparent sample components with a mobility higher than that of the system peak migrate as a pos. peak, whereas UV-transparent components with lower mobilities migrate as neg. peaks. System peaks themselves can also be peaks or dips depending on the sample compn. Sample peaks in the vicinity of system peaks interact with the system peaks through which both sample and system peaks are enlarged and quant. properties are lost. Similar phenomena can be measured for anions in background electrolytes contg. the co-ions phenylacetate and acetate, indicating that these phenomena are probably not assocd. with adsorption phenomena of cations on the fused-silica surface. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)153-165
JournalJournal of Chromatography, A
Issue number1
Publication statusPublished - 1994


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