ON-LINE ELECTROCHEMICAL DETECTION FOR SUPERCRITICAL-FLUID CHROMATOGRAPHY

A self-contained electrochemical cell consisting of a working and a quasi-reference electrode coated with a thin film of a conductive polymer was used as a postcolumn detector for supercritical fluid chromatography (SFC-EC). Cyclic voltammetry was used to obtain chromatograms of ferrocene, anthracene, p-benzoquinone, and hydroquinone after their elution from a Cls packed column with unmodified, acetonitrile-modified, or methanol-modified CO2. In unmodified CO2, the quantitative performance of the SFC-EC detection of ferrocene was similar to that obtained with a downstream mo with respect to detection limit, response linearity, and peak shape. The baseline signal of the EC detector remained hat during density gradient elution while a noticeable drift occurred in the baseline signal of the FID. Furthermore, whereas the mo was totally inoperable in a mobile phase containing similar to 3% (v/v) Of either acetonitrile or methanol, the EC detector functioned well in the modified fluids. Thus, the EC detector is compatible with both unmodified and modified CO2 mobile phases. A valuable feature of these newly developed SFC detectors is their compatibility with a very large fraction of the range of separation conditions that are important to SFC.