Electrosorptive Detection of Simple Organic Compounds in Liquid Chromatography

摘要

The detection of a range of neutral organic compounds in liquid chromatography based on decreases in differential double-layer capacitance, delta C(d), at a mercury-aqueous interface caused by analyte specific adsorption is described. The arrangement employs ac phase-selective measurements using a large-volume wall-jet configuration. The low-molecular-weight organic solutes examined include aliphatic alcohols, diols, mono- and dicarboxylic acids, amines, and alkanolamines. The differential capacitance measurements were conducted close to the potential of zero charge, where adsorption of such species is most extensive. Plots of delta C(d) versus analyte concentration were generally sigmoidal, in accordance with expectations from the Frumkin adsorption isotherm. A potential-step coulometric method, where variations in the nonfaradaic charge. Delta(delta q), are measured, was found to be a useful alternative detection scheme. Methods based on measuring transient capacitive currents associated with tensammetric adsorption-desorption behavior were also briefly investigated.