Fast supercritical fluid chromatography of polymers using packed capillary columns

Fast supercritical fluid chromatography hydrocarbon group-type separations of diesel fuels using packed and monolithic columns

Two approaches for decreasing diesel hydrocarbon group-type separation times by normal phase supercritical fluid chromatography (SFC) are compared. Short (10-15 cm) columns with small 3 microm diameter packing are compared with monolithic Chromolith bare silica columns under high carbon dioxide flow rates approaching 5 ml min(-1). Elution times are reduced up to 13-fold on a 10 cm Chromolith column and 7-fold on the short packed columns compared with conventional length columns run at typical flow rates. Short packed columns, with their higher surface area and retention characteristics, offer higher resolutions compared with Chromolith columns. Diesel samples are separated into saturates, mono-, di-, tri-, and polyaromatics in as little as 2 min on a 10 cm packed silica column. Diesel group-type results on a 15 cm titania-silica coupled column compare favorably with results from longer columns.

Separation of copolymers using high-performance liquid chromatography with polymeric stationary phase and liquefied carbon dioxide as adsorption promoting solvent

Chromatographic separation of copolymers depending on the chemical composition was studied by a solvent gradient method using liquefied carbon dioxide (CO2) as an adsorption promoting solvent. As the high polar stationary phase, non-bonded silica gel, crosslinked acrylamide (AA) gel and crosslinked acrylonitrile (AN) gel were utilized. All columns showed the typical normal phase type of adsorption. Polymeric stationary phases showed the higher sample recovery for styrene-methyl methacrylate (St-MMAs) copolymers, indicating suitability for quantitative analyses. The separations of butyl methacrylate (BMA)-methyl methacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (FBMA)-methy methacrylate copolymers were also carried out, and the latter copolymers were separated based on the CO2-philicity with acrylonitrile column.

Chemical compositional separation of styrene-methyl methacrylate copolymers using high-performance liquid chromatography with liquefied carbon dioxide as eluent

Chromatographic separation of styrene-methyl methacrylate (MMA) copolymers depending on the chemical composition was studied using liquefied carbon dioxide as an adsorption promoting solvent, and tetrahydrofuran, chloroform containing ethanol as a desorption promoting solvent in the mobile phase and the column packed non-bonded silica gel by a solvent gradient method. With the increase of MMA content, the elution was retarded indicating that the typical normal-phase type of adsorption occurred. The effects of type of desorption solvents, molecular mass of sample, and column temperature on the elution were investigated.