Indirect Pulsed Electrochemical Detection following High-Performance Reversed-Phase Liquid Chromatography

Publication date: Available online 14 February 2019

Source: Talanta

Author(s): Loryn R. Keating, William R. LaCourse

Abstract

For detection using pulsed electrochemical detection (PED), analytes must preadsorb to the working gold electrode. Indirect pulsed electrochemical detection (InPED) exploits this requirement by including a PED-active reagent in the mobile phase. The background signal provided by oxidation of this reagent is attenuated by the adsorption of analyte molecules to the electrode. In this paper, a method has been developed to allow the use of InPED in combination with high-performance reversed-phase liquid chromatography (RPLC). Biotin was used as a probe molecule to determine that the use of acetonitrile as the organic modifier in the mobile phase provided superior results to the use of methanol. In addition, a silica-based, high surface area C18 column (i.e., Varian Pursuit XRs) was found to give better results than a polymer-based reversed-phase column (i.e., Dionex IonPac NS1). Optimized experimental conditions were used todetermine lipoic acid, tiopronin, and penicillamine, obtaining detection limits of ≤1 μM (30 pmol injected). The analytical utility of RPLC-InPED was demonstrated by an assay of an over-the-counter-formulation containing lipoic acid.

Graphical abstract

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