title: Chloride present in biological samples as a tool for enhancement of sensitivity in capillary zone electrophoretic analysis of anionic trace analytes.
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 mM mandelic acid and epsilon -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.
authors.affiliation: Institute of Analytical Chemistry, Academy of Sciences of the Czech Republic, Brno, Czech Republic. krivankova@iach.cz
authors.forename: Ludmila
authors.initials: L
authors.lastname: Krivánková
authors.forename: Pavla
authors.initials: P
authors.lastname: Pantůcková
authors.forename: Petr
authors.initials: P
authors.lastname: Gebauer
authors.forename: Petr
authors.initials: P
authors.lastname: Bocek
authors.forename: Jitka
authors.initials: J
authors.lastname: Caslavska
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Thormann
mesh_terms: D000838:Anions / Q000097:blood / Q000302:isolation & purification; D001826:Body Fluids / Q000737:chemistry*; D002264:Carboxylic Acids / Q000097:blood / Q000302:isolation & purification; D002712:Chlorides / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods* / Q000592:standards
chemical_list: D000838:Anions; D002264:Carboxylic Acids; D002712:Chlorides