Integrating HPLC and Electrochemistry: A LabVIEW-Based Pulsed Amperometric Detection System

Abstract

A unique set of experiments coupling the fundamental principles of electrochemistry and liquid chromatography is described for the undergraduate instrumental analysis laboratory. Students begin by examining the voltammetric behavior of glucose in alkaline solution at a gold rotating-disk electrode (RDE). The results are applied to the development of an analytical method for the determination of glucose, fructose, and sucrose in fruit juices. These weakly acidic sugars are easily separated in alkaline solution using anion-exchange HPLC. The detection of these compounds, however, has presented some challenges. Their poor spectroscopic properties result in insensitive UV absorbance detection, and traditional constant-potential electrochemical detection is ineffective because products of the oxidation reactions remain adsorbed to the electrode surface, rendering it inactive. However, electrochemical detection is effective if the working electrode is subjected to a repeated series of potential pulses that alternately detects the analyte and cleans the electrode. Students use the glucose RDE data to construct this pulsed amperometric detection (PAD) waveform, and then use LabVIEW to both apply the waveform to the electrode and monitor the electrode current.