ANALYSIS OF ALIPHATIC AND PHENOLIC CARBOXYLIC-ACIDS BY CAPILLARY SUPERCRITICAL FLUID CHROMATOGRAPHY FOURIER-TRANSFORM INFRARED MICROSPECTROMETRY

A mobile phase elimination interface and a microscope accessory are used to combine capillary supercritical fluid chromatography with Fourier-transform infrared spectrometry for analyzing carboxylic acids. Separations of a mixture of oligomers prepared by a self-condensation polymerization of 12-hydroxystearic acid and of a mixture of 16 phenolic carboxylic acids are achieved by using a well-deactivated fused-silica capillary column coated with an oligoethyleneoxide substituted methylpolysiloxane (glyme) stationary phase and carbon dioxide as the mobile phase. Components requiring identification are deposited, with elimination of the carbon dioxide, onto potassium bromide discs as compact spots, from the end of a heated restrictor, which is attached at the end of the column. Unique spectroscopic information is obtaned by positioning the spots in the microscope and measuring their infrared spectra. Phenolic acids are unambiguously identified and the degree of polymerization of oligomers in the 12-hydroxysteric acid reaction mixture is indicated from the ratio of ester carbonyl to acid carbonyl absorptions. © 1990.