8 August / September 2019


A major source of confusion appears to revolve around injection volume, selection of injection solvent, and the interactions between the sample, sample solvent, and their competition for sites on the stationary phase. On these small ID columns, efficient injections tend to be limited to very small volumes. While recent reports [22,23] have started to clarify some of these issues more work is needed.


The path forward seems fairly clear. Decreasing the extra-column variance by miniaturising tubing ID, length, and detector flow cell volumes is effective, but is not yet optimised. More effort is needed in optimising sample solvent characteristics to both the solutes and stationary phase. We need consistently more efficient columns of the appropriate dimensions. Fortunately, this seems to be getting better. It is hoped that the works summarised here, combined with future works, will eventually result in the instrument manufacturers producing a true UHPSFC.


References


1. Halasz, I., Endele, R., Asshauer, “Ultimate limits in high-pressure liquid chromatography” J., (1975) J. Chromatogr. 112, 37-60.


2. Horvath, C., Lin, H.J., “Band spreading in liquid chromatography: General plate height equation and a method for the evaluation of the individual plate height contributions”, (1978) J. Chromatogr. 149, 43-70.


3. de Villiers, A., Lauer, H., Szucs, R., Goodall, S., and. Sandra, P., Influence of frictional heating on temperature gradients in ultra-high-pressure liquid chromatography on 2.1 mm I.D. columns”, (2006), J. Chromatogr. A, 1113, 84-91.


4. Terry A. Berger, “Clarifying the Relationship Between Density and Viscosity of Methanol/Carbon Dioxide Mixtures used in Supercritical Fluid Chromatography”, Chromatography Today, Feb/March, 2019, pp. 28-31.


5. Sam O. Colgate, Terry A. Berger, “On axial temperature gradients due to large pressure drops in dense fluid chromatography”, 2015, J. Chromatogr. A, 1385, 94-102.


6. Perrenoud A.G-G., Veuthey, J-L. Guillarme, D., “Comparison of ultra- high performance supercritical fluid chromatography and ultra-high


performance liquid chromatography for the analysis of pharmaceutical compounds”, 2012, J. Chromatogr. A, 1266, 158-167.


7. Alexandre Grand-Guillaume Perrenoud, Chris Hamman, Meenakshi Goel, Jean-Luc Veuthey, Davy Guillarme, Szabolcs Fetkete, “Maximizing kinetic performance in SFC using state-of-the-art instruments”, 2013, J. Chromatogr. A, 1314, 288-297.


8. Ruben De Pauw, Konstantin Shoykhet, Gert Desmet, Ken Broeckhoven, “Understanding and diminishing the extra-column band broadening in supercritical fluid chromatography”, 2015, J.Chromatogr. A, 1403, 132-137.


9. Terry A. Berger, “Demonstration of high speeds with low pressure drops using 1.8 µm Particles in Supercritical Fluid Chromatography (SFC)”, Chromatographia, 72 (2010) 596-602.


10. Terry A. Berger, “Characterization of a 2.6 µm Kinetex porous shell hydrophilic interaction liquid chromatography column in supercritical fluid chromatography with a comparison to 3µm totally porous silica”, 2011, J. Chromatogr. A, 1218, 4559-4568.


11. Chandran L. Barhate, M. Farooq Wahab, D.J. Tognarelli, Terry A Berger, Daniel W. Armstrong. “Instrumental Idiocyncracies Affecting the Performance of Ultrafast Chiral and Achiral Supercritical Fluid chromatography”, 2016, Anal. Chem., 88, 8664-8674.


12. Terry A. Berger, “Instrument modifications that produced reduced plate heights < 2 with sub-2 µm particles and 95% of theoretical efficiency at k = 2 in supercritical fluid chromatography”, 2016, J. Chromatogr. A, 1444, 129-144.


13. Terry A. Berger, “Kinetic performance of a 50 mm long 1.8 µm chiral column in supercritical fluid chromatography”, 2016, J. Chromatogr. A,1459, 136-144.


14. Terry A. Berger, “Preliminary kinetic evaluation of an immobilized polysaccharide sub-2 µm column using a low dispersion supercritical fluid chromatograph”, 2017, J. Chromatogr. A, 1510, 82–88.


15. Omar H. Ismail, Gioacchino L. Losacco, Giulia Mazzoccanti, Alessia Ciogli, Claudio VillaMartina Catani, Luisa Pasti, Scott Anderson, Alberto Cavazzini, and Francesco Gasparrini, “Unmatched Kinetic Performance in Enantioselective


Supercritical Fluid Chromatography by Combining Latest Generation Whelk-O1 Chiral Stationary Phases with a Low-Dispersion in-House Modified Equipment”, 2018, Anal. Chem., 90, 10828-10836.


16.] Ruben De Pauw, Konstantin Choikhet, Gert Desmet, Ken Broeckhoven, “Occurrence of turbulent flow conditions in supercritical fluidchromatography”, 2014 J. Chromatogr. A 1361 277–285.


17.] Terry A. Berger, “Characterizing pressure issues due to turbulent flow in tubing, in ultra-fast chiral supercritical fluid chromatography at up to 580 bar”. 2016, J. Chromatogr. A, 1475, 86-94.


18.] Terry A. Berger. “High Speed, High Efficiency Achiral SFC on a 3x20 mm Column Packed with 1.8 µm Particles Facilitated by a Low Dispersion Chromatograph”, 2019, Chromatographia, 82, 537-542; DOI 10.1007/s10337-018- 3655-5.


19.] Terry A. Berger, “Reduced Plate Height of 1.65 on a 20x3 mm column packed with 1.8 µmParticles in Supercritical Fluid Chromatography” Chromatographia, accepted April 2019.


20.] A.C. Sanchez, J.A. Anspach, T. Farkas, “Performance optimizing injection sequence for minimizing injection band broadening contributions in high efficiency liquid chromatographic separations”, J. Chromatogr. A 1228 (2012)338-348.


21.] James C, Sternberg, “Extracolumn Contributions to Chromatographic Band Broadening”, in Advances in Chromatography, Vol.2, J.C. Giddings, R.A. Keller, eds., Marcel Dekker, New York, 1966, Chapter 6.


22.] Martin Enmark, Dennis Åsberg, Andrew Shalliker, Jörgen Samuelsson, Torgny Fornsted “A closer study of peak distortions in supercritical fluid chromatography as generated by the injection” J. Cromatogr. A, 1400, 2015, 131-139.


23.] Vincent Desfontaine, Abhijit Tarafder,Jason Hill, Jacob Fairchild, Alexandre Grand-Guillaume Perrenoud,, Jean-Luc Veuthey, Davy Guillarme, “A systematic investigation of sample diluents in modern supercritical fluid chromatography” J. Chromatogr. A, 1511 (2017) 122-131


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