PACKED CAPILLARY COLUMN SOLVATING GAS-CHROMATOGRAPHY USING MOBILE PHASES THAT TRANSITION FROM LIQUID TO GAS BETWEEN THE COLUMN INLET AND OUTLET

In this study, organic solvents at temperatures higher than their norm al boiling points were used as mobile phases for packed capillary colu mn chromatography. No restrictor or back pressure was imposed on the c olumn outlet. As a result, a large difference in mobile-phase properti es existed, and a phase transformation from liquid to gas occurred, al ong the column. Solvating gas chromatography (SGC) was used to charact erize this chromatographic process because, near the column outlet, a gaseous mobile phase existed. Chromatographic performance characterist ics including mobile-phase now, column efficiency, mobile-phase solvat ing power, and solute retention were investigated using fused-silica c apillary columns packed with microparticles (5- and 10-mu m diameters) . It was found that when the temperature was increased to values that were higher than the normal mobile-phase boiling point, the mobile-pha se linear velocity increased rapidly at constant column inlet pressure . Although large differences in mobile-phase properties existed betwee n the column inlet and outlet, high column efficiencies (reduced plate heights of less than 2) were achieved. At elevated temperature, the o ptimum mobile-phase linear velocity increased, and the dependence of c olumn efficiency on linear velocity decreased, Solute retention factor s also decreased with increasing temperature, even for temperatures hi gher than the normal boiling point of the mobile phase. Large polycycl ic aromatic hydrocarbons and enantiomers were rapidly separated under SGC conditions.