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Chloride present in biological samples as a tool for enhancement of sensitivity in capillary zone electrophoretic analysis of anionic trace analytes
Author(s) -
Křivánková Ludmila,
Pantůčková Pavla,
Gebauer Petr,
Boček Petr,
Caslavska Jitka,
Thormann Wolfgang
Publication year - 2003
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200390059
Subject(s) - isotachophoresis , chemistry , stacking , analyte , chromatography , detection limit , electrolyte , chloride , capillary electrophoresis , analytical chemistry (journal) , organic chemistry , electrode
Abstract Effects originating from the variability of the sample matrix can be efficiently eliminated when the separation conditions are selected so that compounds of like charge with high concentration referred to as macrocomponents are embodied into the system of transient isotachophoresis. For stacking and separation of anionic trace analytes in biological samples, the presence of chloride is shown to be important to balance out effects of other macrocomponents that act against isotachophoretic stacking. Having acetoacetate, malate, citrate, and some drug metabolites in untreated human serum samples, the stacking mechanism of these compounds in an electrolyte system comprising 5 m M mandelic acid and ε‐aminocaproic acid, pH 3.8, is explained. Analytes are monitored by indirect UV‐absorption detection. Attention is paid to the minimum chloride concentration required with respect to the concentration ratio of phosphate (stacker) and lactate (destacker) present in the sample so as to ensure both stacking and separation of trace analytes. Insight into the separation process is given both with computer simulations and experiments. For selected analytes, the effect of chloride concentration on quantitative evaluation, sensitivity and limit of detection is demonstrated as well. Moreover, the applicability of the mobility window between phosphate and lactate for an additional group of metabolites is sketched.