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High-Speed, High-Efficiency Achiral SFC on a 3 × 20-mm Column Packed with 1.8-µm Particles Facilitated by a Low-Dispersion Chromatograph

Berger, Terry A.
Chromatographia 2019 v.82 no.2 pp. 537-542
chromatography, methanol, silica, solutes, solvents
There are almost no reports using 20–30 mm long (or shorter) columns packed with sub-2 µm packings for SFC separation of achiral solutes in the literature, probably because current commercial SFCs have extra-column dispersion of > 80 µL². A modified supercritical fluid chromatograph (SFC) with extra-column dispersion below 5 µL² produced reduced plate heights as low as 2.2, using a 3 × 20-mm column packed with 1.8-µm RX-Sil, bare silica particles, with 7.5% methanol at 2.5 mL min⁻¹. The calculated and observed peak fidelities were similar at ≈ 0.85 suggesting the chromatographs extra-column dispersion was slightly limiting the observed efficiency, which suggests the column might be even better packed. Increasing the flow rate to 5 mL min⁻¹ with 15% methanol resulted in the resolution of 7 solutes, from 4 different solute families, in less than 8 s. A few of the peaks required a UV detector filter setting of 120 Hz (< 0.016 s. response time) to avoid extra-column peak broadening. The column was quite susceptible to the strong sample solvent effect. Even moderate sized injection volumes (of MeOH) and feed volumes (of IPA) degraded efficiency significantly.