Manipulation of the Chromatographic Retention of p-Benzoquinone and Dihydroxybenzene Isomers in On-line Redox Derivatization Liquid Chromatography Using Electrochemical Flow Cell

Abstract

On-line redox derivatization liquid chromatography (ORDC) was applied to the analysis of p-benzoquinone and dihydroxybenzene isomers (hydroquinone, catechol, and resorcinol). The ORDC system used is an HPLC system consisting of two separation columns and an electrochemical flow cell as a redox derivatization unit placed between them. A redox derivatization reaction proceeds in the electrochemical flow cell so that an analyte compound migrates in its original form in the first column, while it moves in its oxidized or reduced form in the second column. The manipulation of chromatographic retention of the analyte can be performed by adjusting the lengths of the two columns because redox reactions specific to the analyte in the electrochemical derivatization unit can be controlled by alteration of the potential applied to the cell. Hydroquinone, catechol, and p-benzoquinone injected into the system were completely converted to chemical species that are redox couples in the electrochemical flow cell to which a given potential was applied. Selective separations of p-benzoquinone from hydroquinone, catechol and resorcinol were demonstrated by the ORDC system. The method was successfully applied to the analysis of trace p-benzoquinone in a hydroquinone reagent.