Peak compression in semi-preparative supercritical fluid chromatography

Peak compression of a dihydropyridine drug, clevidipine, is obtained in bot h analytical and semi-preparative scale supercritical fluid chromatography, resulting in extremely high apparent efficiencies. The observed effect, wh en utilising a carbon dioxide/2-propanol mobile phase with a bare silica st ationary phase, is achieved when the retention of the clevidipine peak is c ontrolled to coalesce with a system peak, generated as a result of having w ater in the sample. Apparent efficiencies of 350,000 and 170,000 plates met er(-1) were obtained when 0.25 and 0.5 mg, respectively, are directly injec ted to a 200 x 4.6 mm ID 5 mu m Hypersil silica packed column. The effect w as extended to a semi-preparative system where apparent efficiencies in the region of 2,000,000 plates meter-l were observed when 0.3 mg of a clevidip ine sample containing 80 % water was injected to a 250 x 10 mm I.D. column containing 5-mu m Hypersil silica particles.