Supercritical Fluid Chromatography SFE

SFC of PAHs has been extensively reviewed.225 SFC combines the speed and efficiency of GC with the stationary-phase interactions possible in HPLC. PYR, B[a]A, 1-nitropyrene, and B[a]P in an explosives residue were separated on a 6 m X 50 ^m i.d. open tubular column coated with 0.1 /Am p,p-cyanobiphenyl polysiloxane with supercritical CO2 as the mobile phase.226 Solidphase injection was required due to the effects of solvent on selectivity in SFC. Seven PAHs were identified in a mixture of explosives on a 25 cm X 250 ^m microcolumn packed with poly(octylhydrosiloxane) polymer stationary phase.227 No modifier was added to pure supercritical CO2 at 100°C and a density program of 0.14 to 0.64 g ml" Separation was achieved in approximately 60 min. Five 20 cm X 4.6 mm Hypersil silica columns connected in series served as the stationary phase for a separation using CO2 at a flow rate of 1.5 ml min"1 and 40°C modified with methanol from 2 to 10%, and an initial pressure of 100 bar increasing to 150 bar.228 PAHs in water have been measured using SFC with diode array detection (DAD) following online concentration by solid-phase extraction.229 A 15 cm X 4.6 mm Spherisorb 5-^im ODS2 column and a 125 mm X 4.6 mm Envirosep-PP 5-^im column were connected in series. They were operated at 40°C and 200 bar. A flow rate of 2.5 ml min"1 of CO2 modified with a methanol gradient allowed for resolution of the EPA16 in 14 min with LODs of 0.1 to

0.8 mg 1"Preconcentration on C18 extraction disks showed recoveries of >70% with a concentration factor of about 1000.

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