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C190-E200

Technical

Report Supercritical Fluid Chromatography

Hidetoshi Terada , Takato Uchikata , Takanari Hattori , Keiko Matsumoto , Yoshiyuki Watabe ,
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Tadayuki Yamaguchi , Yasuhiro Funada 1
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Abstract:
Advances in column technology have led to a renewed interest in supercritical ˜uid chromatography, which uses a supercritical ˜ uid as its
mobile phase. Compared to liquid, supercritical ˜uids have low viscosities and high diffusivities. In this report, starting from the basic
principles of supercritical ˜uid chr omatography, we introduce examples of high-speed, high-resolution analysis and chiral separation.

Keywords: supercritical uid chromatography, SFC

1. Supercritical Fluid
1. Super critical Fluid 25
Water
A supercritical fluid is a state of substance wherein the temperature
and pressure are both above its critical point (Fig. 1). Supercritical
fluids can dissolve substances better than gases and are more diffu-
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sive and have lower viscosities than liquids (Table 1). Although various Critical pressure (MPa) 20
substances have particular critical points, the especially low critical
point of carbon dioxide (critical temperature: 31.1°C, critical pres- 10 Carbon dioxide Methanol
sure: 7.38 MPa) makes it easy to handle. As it is non-flammable, inert, Ethylene
low-cost, and non-toxic, it has been widely used in industrial process- 5 Propylene Ethanol
es, such as for decaffeination of coffee beans and extraction of hops Methane Ethane Propane Acetone
extract and flavor compounds (Fig. 2). Supercritical fluids are also
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used in analytical fields, including as the main mobile phase in super- −100 0 100 200 300 400
critical fluid chromatography (SFC) and the main extracting solvent in Critical temperature (°C)
supercritical fluid extraction (SFE). Fig. 2 Critical Points of Various Substances

2. Supercritical Fluid Chromatography
Supercritical
Solid Liquid ˜uid
SFC is a separation technique that uses a supercritical ˜uid as its main
Critical pressure mobile phase (often supercritical carbon dioxide). Because of the prop-
7.38 MPa Critical point erties of supercritical ˜uids, which include low viscosities and high dif-
fusivities, SFC can be performed at a lower column back pressure than
Gas conventional high-performance liquid chromatography (HPLC). Addi-
tionally, a high-speed analysis can be performed at high ˜ow rates and
Critical temperature a high-resolution analysis can be performed by using a longer column.
31.1°C Also, recent advances in SFC systems and in the packed columns made
Fig. 1 Phase Diagram for Carbon Dioxide for SFC allow analyses to be performed with HPLC-like operation.
Although supercritical carbon dioxide has a similar hydrophobicity as
hexane, this property alone is often insufÿcient for the elution of
Table 1 Properties of Supercritical Fluids
target compounds from a column. These target compounds can be
Diffusion coef cient Density Viscosity eluted by adding an organic solvent, called a modiÿer, to modify the
(cm /s) (g/cm ) 3 (g/cm • s)
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polarity of the mobile phase. Organic solvents that are compatible
Liquid 10 −6 1 10 −2 with carbon dioxide, such as methanol, ethanol, isopropyl alcohol,
Supercritical uid 10 −3 0.2 to 0.8 10 −3 and acetonitrile, are used as modiÿers. Organic solvents with an
Gas 10 −1 10 −3 10 −4 added acid (e.g., formic acid or acetic acid), salt (e.g., ammonium for-
mate or ammonium acetate), or base (e.g., diethylamine) are also
used as modiÿers for the analysis of highly polar compounds.

1 Analytical & Measuring Instruments Division 1