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.