Publication details
NEAR-COULOMETRIC ELECTROCHEMICAL DETECTOR WITH DISPOSABLE PENCIL GRAPHITE ELECTRODE FOR FIA AND HPLCNEAR-COULOMETRIC ELECTROCHEMICAL DETECTOR WITH DISPOSABLE PENCIL GRAPHITE ELECTRODE FOR FIA AND HPLC
| Authors | |
|---|---|
| Year of publication | 2019 |
| Type | Article in Proceedings |
| Conference | XX Euroanalysis |
| MU Faculty or unit | |
| Citation | |
| Keywords | pencil graphite electrode; FIA; HPLC; gentisic acid; caffeic acid; dihydrocaffeic acid; near-coulometric detector |
| Description | We report on a concentric thin layer cell accommodating pencil graphite disposable working electrode with a non-standard diameter of 0.2 mm (Pentel Ain Stein, Japan). Prior to flow experiments, electrochemical properties of the pencil leads were investigated using cyclic voltammetry of potassium ferricyanide in aqueous and ferrocene in non-aqueous environment with the result that the 0.2 mm pencil graphite surface surface has a character of microelectrode array. Then, the pencil lead was applied in in-house designed flow cell which was tested in conventional HPLC setup. Operation in mobile phases containing both low and high content of organic solvents provided satisfactory results in HPLC analyses of phenolic acids and tocopherol isomers was investigated. HPLC separation of model mixtures of gentisic, caffeic and dihydrocaffeic acids showed a remarkable electrolytic efficiency exceeding 80% at 200, and 50% at 500 µL/min, while for gentisic acid the limit of detection (LOD) was 0.4 nmoL L-1 at 20 microliter sample loading (8 fmoL on-column). Similar LODs (e.g. 0.8 nmoL L-1 for delta-tocopherol) were found in the model separation of tocopherol isomers in non-aqueous mobile phase. The developed flow-through detector allows an easy replacement of pencil graphite working electrode in a highly reproducible manner. The relative standard deviation for the HPLC analysis of tocopherol isomers was of 5.3% (n=3, C=500 nmoL L-1). Near-coulometric operation at normal flow rates and sub- or nanomolar detection limits was demonstrated for mobile phases containing low and high content of organic solvents.The combination of simple construction, excellent electrochemical performance and hydrodynamics identical to that of commercial UV-VIS HPLC detector suggests that the proposed device is a viable low-cost alternative to commercially available electrochemical detectors. |