Separation of Large Coal Molecules Using High Resolution Supercritical Fluid Chromatography. Final Report March 1982 - April 1985

摘要

Capillary supercritical fluid chromatogr aphy was developed and evaluated for the application to large coal-derived molecules. Chromatographic theory was developed for supercritical fluid mobile phases, and formed the basis for selection of operating parameters for the technique. Capillary columns of less than 100-micrometer i.d. and with stationary phase films up to 1 micrometer in thickness produced chromatographic efficiencies in excess of 3,500 plates/m at ten times the optimum linear velocity. These columns were prepared from fused silica tubing which was deactivated at 450 C with hexamethyldisilazane or hexamethyldisiloxane, coated with various polysiloxane stationary phases, and crosslinked with azo-t-butane in order to render the stationary phase insoluble. Polysiloxanes containing biphenyl, cyanopropyl, and n-octyl side groups were synthesized for use as stationary phases. Hardware and microcomputer software were developed for density programming of the syringe pump during chromatographic analysis. An optical fiber-based scanning fluorescence detector with sub-picogram sensitivity was constructed. The common flamebased gas chromatographic detectors, flame ionization, flame photometric, and thermionic, as well as a mass spectrometer, were successfully interfaced to the supercritical fluid chromatograph. Pure supercritical n-pentane was found to be the best mobile phase for coal-derived materials, and the technique was successfully applied to several samples which were beyond the range of gas chromatography.