Glenne E, Leśko M, Samuelsson J, Fornstedt T. Impact of Methanol Adsorption on the Robustness of Analytical Supercritical Fluid Chromatography in Transfer from SFC to UHPSFC.
Anal Chem 2020;
92:15429-15436. [PMID:
33170667 PMCID:
PMC7711781 DOI:
10.1021/acs.analchem.0c03106]
[Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
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In supercritical fluid chromatography
(SFC), the retention of a
solute depends on the temperature, density, pressure, and cosolvent
fraction. Here, we investigate how the adsorption of the cosolvent
MeOH changes with pressure and temperature and how this affects the
retention of several solutes. The lower the pressure, the stronger
the MeOH adsorption to the stationary phase; in addition, at low pressure,
perturbing the pressure results in significant changes in the amounts
of MeOH adsorbed to the stationary phase. The robustness of the solute
retention was lowest when operating the systems at low pressures,
high temperatures, and low cosolvent fractions in the eluent. Here,
we found a clear relationship between the sensitivity of MeOH adsorption
to the stationary phase and the robustness of the separation system.
Finally, we show that going from classical SFC to ultrahigh-performance
SFC (UHPSFC), that is, separations conducted with much smaller packing
diameters, results in retention factors that are more sensitive to
fluctuations in the flow rate than with traditional SFC. The calculated
density profiles indicate only a slight density drop over the traditional
SFC column (3%, visualized as lighter → darker blue in the
TOC), whereas the drop for the UHPSFC one was considerably larger
(20%, visualized as dark red → light green in the TOC). The
corresponding temperature drops were calculated to be 0.8 and 6.5
°C for the SFC and UHPSFC systems, respectively. These increased
density and temperature drops are the underlying reasons for the decreased
robustness of UHPSFC.
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