Supercritical carbon dioxide (scCO₂) has interesting solvent properties in terms of gas-like viscosity and tunable density. Due to its low polarity, a polar organic solvent is usually added as a modifier, e.g. methanol, ethanol, and/or water in small amounts. Fundamental physicochemical properties of binary (CO₂+organic solvent) and ternary (CO₂+organic solvent+water) solvent mixtures have been studied in the literature by us [1-2] and others [3]. However, there are still knowledge gaps in terms of density, viscosity and dielectric properties of mixtures containing over 0.5 molar fraction of organic solvent, with or without water added. Often, such solvent mixture is called a gas expanded liquid [4]. In extraction and chromatography, selectivity is highly relevant, especially for complex samples. It is well known that supercritical fluid chromatography (SFC) offers higher selectivity than LC, mainly due to the polarity and functionality that stationary phases in SFC offer. In supercritical fluid extraction (SFE), selectivity is more challenging to describe quantitatively. Comprehensiveness is another interesting concept. In untargeted analysis, it is of interest to achieve complete extraction of wide ranges of chemically different analytes, without losing quality of the chromatography. Similarly, comprehensiveness in SFC is also of interest, as discussed in terms of unified chromatography [5]. In this lecture, selectivity and comprehensiveness of SFE and SFC will be discussed for phenolic compounds in lignin, coal, and seaweed samples, vitamin D metabolites in adipose tissue, and emerging pollutants in environmental samples.
1. L. P. Cunico and C. Turner, J. Chem. Eng. Data, 2017, 62, 3525–3533.
2. L. P. Cunico, et al., J. Supercrit. Fluids, 2017, 130, 381–388.
3. F. Pena-Pereira and M. Tobiszewski, Eds., Elsevier, ISBN 978-0-128-05297-6, 2017.
4. P. Jessop and B. Subramaniam, Chem. Rev. 2007, 107, 2666–2694.
5. K. Taguchi et al., J. Chromatogr. A, 2014, 1362, 270–277.

Daniel Papp

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