Determination of carbohydrates by capillary zone electrophoresis with amperometric detection at a copper microelectrode

Abstract

Capillary zone electrophoresis (CZE) was employed to separate sugars according to their electrophoretic mobilities In strong alkaline solutions (pH ca. 13). Saccharide zones were monitored electrochemlcally using amperometric detection at a constant potential, 0.6 V (vs Ag/AgCI), with a cylindrical copper wire electrode (25 pm In diameter). The Cu-wlre microelectrode In strong basic solutions had electrochemical behavior similar to that of Cu electrodes with larger dimensions and appeared to show no deterioration for hundreds of runs. A sample mixture containing 15 different sugars was separated In less than 45 min with separation efficiencies up to 200 000 theoretical plates. The calibration plot was found to be linear over 3 orders of magnitude and the limits of detection for the saccharides studied were In the femtomole range.

Recent Developments in Liquid Chromatography and Capillary Electrophoresis for the Analysis of Glycoprotein Glycans

“…The separated carbohydrates are sometimes detected by electrochemical detection (ECD) or PAD on a metal electrode. 144,145 The detection limit of these methods can reach femtomole levels. Alternatively, indirect detection can also be employed, using various fluorescent dyes including fluorescein and coumarins for sensitive detection.…”

Detecção eletroquímica em eletroforese capilar

“…Sistemas mais sofisticados envolvendo a remoção 40,52,157 , enzimas e proteínas [160][161][162] , co-fatores 163 , nucleotídeos e similares [164][165][166] , ácidos policarboxílicos 167 , hormônios 168 , bem como outros metabólitos, como ácido úrico 169 [197][198][199][200][201] . A ED também é bastante apropriada em separações eletroforéticas em meio não-aquoso (NACE), uma vez que a maioria dos solventes utilizados absorve fortemente na região do UV, o que dificulta as medidas fotométricas.…”

Sensitive determination of sugars by capillary zone electrophoresis with indirect UV detection under highly alkaline conditions

“…Since most sugars have a pK a value between 12 and 13, a high pH of the electrolyte is required for their separation [15][16][17][18]. The conductivity of the medium increases with the pH and the resulting high electrophoretic currents are accompanied with baseline instabilities and low signal-to-noise ratios with indirect UV detection.…”

“…It was found that a number of di-and trisaccharides as well as aldonic acids still could not be derivatized successfully [14]. (c) With an electrochemical detector, underivatized sugars can be detected sensitively by a pulsedpotential technique with a gold electrode [15] or at a constant detection potential with copperbased electrodes [16,17]. A high pH (12)(13) solution is necessary for the separation as well as for the detection.…”