Abstract
The plumbing of a commercial supercritical fluid chromatograph was modified by replacing all the connector tubing with the shortest possible lengths (65 cm) of 75 µm ID tubes. Heat exchangers controlling column temperatures and column outlet temperature were bypassed. The UV detector flow cell was replaced with an experimental cell with a 75 µm inlet tube, and a 2 µL internal volume. All these steps were taken to minimize extra-column dispersion. The extra-column dispersion was decreased from ≈ 80 µL2 in the commercial instrument to roughly 2 µL2 with the modifications. Reduced plate heights as low as 1.65 were obtained using a 20 × 3 mm column packed with 1.8 µm particles. This is a remarkably low value for such a short column. The optimum flow was ≈ 2.5 mL min−1. The system pressure drop at optimum was 220 bar (320 bar pump pressure), but increased rapidly with flow rate, to 450 bar (550 at pump) at 3.5 mL min−1.
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