Assessment of ion transfer amperometry at liquid–liquid interfaces for detection in CE

Abstract

In this research, ion transfer across the interface between two immiscible electrolyte solutions (ITIES) was used as a method of detection in a CE separation system. This method allows for the electrochemical detection of ionic analytes that cannot be easily oxidized or reduced. Method development revealed that the optimal separation conditions for three model ions (tetraethylammonium, tetrabutylammonium, and benzensulfonate) were found to be 5 mM sodium tetraborate buffer pH 9.2 with a separation voltage of 20 kV using a 40 cm, 50 microm id fused silica capillary. Constant potential amperometry and pulsed amperometric detection were applied at the ITIES in which the organic phase was gelled. A miniaturized ITIES within a pipette tip was investigated, which resulted in improved separation efficiency and LOD. To demonstrate the ability of the system to detect substances of bioanalytical interest, the beta-adrenergic receptor blockers timolol and propranolol were detected. The simplicity of the detection platform means that it may be useful for analytical situations not requiring trace or ultratrace detection capabilities.

Liquid/Liquid Interfaces, Electrochemistry atUpdate based on the original article by Frédéric Reymond, Hubert H. Girault,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd

“…(79) These sensors have successfully been used as detectors for capillary zone electrophoresis, with performance comparable with the state of the art detectors employed usually. (125,126) Recently, an amperometric thin-layer electrochemical flow cell sensor based on membranesupported ITIES was demonstrated for nanomolar detection of TEA + . This technique increased the sensitivity of the amperometric sensors based on ITIES by the factor of 10-1000.…”

Microscopic gel–liquid interfaces supported by hollow microneedle array for voltammetric drug detection

“…Propranolol has already been detected by ion transfer voltammetry at µITIES at concentration levels that are physiologically relevant [25][26][27], thus allowing useful comparison with the results reported here.…”

Electric field‐enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis

“…On the other hand, ITIES was never truly tested for measurements of real samples and this may be the bottleneck of the method as the electrochemical monitoring of the extracted analytes is rather non-selective and might be limited to samples with simple matrices. Coupling ITIES to a suitable separation method might be a solution for analyses of biological and other complex samples and instrumental aspects of such an approach coupling ITIES as a detection technique to CE have been described very recently [116]. EME across SLM is strongly dependent on the chemical composition of the membrane and acceptor phase, which makes it a very selective extraction technique.…”