Microelectrochemical detection in capillary column supercritical fluid chromatography

Oxidative and reductive amperometric detection at a naked platinum microelectrode is shown to be compatible with capillary column supercritical fluid chromatography (SFC) using carbon dioxide modified with low percentages of water, acetonitrile or methanol. The compatibility with various modifiers is important as the use of modified mobile phases in SFC generally results in altered chromatographic selectivity, shorter analysis time and the possibility to analyse more polar compounds. A total number of about 20 different compounds, including, e.g., ferrocenes, phenols and nitroaromatic compounds, have been detected in carbon dioxide based mobile phases with medium to low picogram detection limits. The detector response was linear for injections of between ca. 0.1 and 4 ng of the analytes for both oxidative and reductive detection. The relative standard deviation in the peak height for ng injections of analyte was ca. 5% under both pressure programmed and isobaric conditions.