Potentiometrische Detektion von Komplexbildnern nach Trennung mittels Kapillarzonenelektrophorese

Recent Developments in Electrochemical Detection Methods for Capillary Electrophoresis

“…Buchberger and coworkers have also shown that the detection of the chelating agent diethylenetriaminepentaacetic acid is possible by this means [76]. The operating principle of the copper wire electrodes in the potentiometric mode is presumed to be based on the complexation of free copper ions on the surface.…”

Hydrophobicity‐aided potentiometric detection of catecholamines, beta‐agonists, and beta‐blockers in a mixed‐solvent capillary electrophoresis system

“…Copper wire was used as the working electrode material in sensitive potentiometric detection of aliphatic carboxylic acids [8,17], aminopolycarboxylic acids [14], fatty acids [17], amino acids [9, 15], alkylsulfonic acids [16], common inorganic anions [16], and a limited number of cationic drugs [20] after their separation in conventional aqueous capillary zone electrophoresis systems. The copper wire electrode was used uncoated as a disk [16] or a rod [8,9,14,15,17,20] in the MTE [9, 14 -16] but in PVCbased liquid membrane coated mode as the CWE [8,20], the conducting polymer electrode (CPE) employs electrodeposited phenylene-vinylene oligomer [17] or polypyrrole polymer [17].…”

“…In addition some food component related compounds such as aliphatic amines and diamines [12,18,20] and quaternary ammonium compounds [20] were detected potentiometrically with the TCPB-containing CWE in CE systems employing 25 or 100 lm id fused silica capillaries and aqueous BGE composed of tetraborate [12], magnesium tartrate [18], or sodium phosphate [20] buffer. It should be noted, however, that in both ISMEs and CWEs the amide-type podant [6,11] or the calixarene-type macrocyclic [20] cation selective ionophores were used as additives to the PVC membrane of the microelectrode, which markedly enhanced (LOD a 10 -7 M) their sensitivity to histamine [14,11], aliphatic amines [20], and some neurotransmitters [6,20] under CE conditions. Interestingly, in addition to histamine, potentiometric detection of other zwitterionic amino acids in CE was accomplished exclusively with the MET type electrodes [9].…”

“…In case of aliphatic carboxylic acids [8,14,17,18], the liquid membrane of the CWE contained quaternary ammonium salts [8] or, alternatively, macrocyclic pentaamine [8] as the selective ionophore. In some cases the membrane of the CWE was formed in situ by applying phenylene vinylene oligomer [17] or polypyrrole polymer [17] directly to the surface of the electrode, which shifted the LODs for acidic solutes in CE systems to 1.0610 -6 M. However, the use and characteristics of potentiometric detection in non-aqueous CE systems, which are beneficial in the separation of hydrophobic basic compounds and acidic drugs [25,26], still appear especially challenging.…”

“…In the case of hydrophilic catecholamines and carbuterol their LODs with potentiometric detection were lowered by a factor of almost one thousand, reaching a value of 6.6610 -5 M. In the last few years, the theoretical principles, analytical features, and practical limitations of potentiometric detection coupled in end-capillary or on-column fashion with various conventional CE systems have been presented in various original [5 -20] and review [3,21] papers. Considering the construction mode, three types of high-impedance working electrodes applicable in CE have been developed, namely micropipette ion-selective microelectrodes (ISME) [5 -11, 13, 15, 18], coated-wire ion-selective electrodes (CWE) [8, 9,12,13,17,18,20], and metallic electrodes (MTE), defined as reactive [9,14,16] or inert [16,19]. However, to our best knowledge, until today potentiometric detection has not been implemented in a CE microchip [21 -23].…”