Supercritical Fluid Extraction and its Use in Chromatographic Sample Preparation

by Professor D. E. Games, Mass Spectrometry Research Unit, University College of Swansea Sample preparation can be viewed as occupying a Cinderella role in analytical science. However, the quality of sample preparation plays a key role in high In the past decade, there has been quality analysis and deserves higher stature. considerable interest in the use of supercritical fluid extraction (SFE) as an alternative to conventional procedures for the preparation of samples for ana lysis. The driving force for this development is the need for automated, sim pler, faster, non-destructive and selective methods for extraction, preferably using non-toxic extraction media which are easily disposed of. Utilization of supercritical fluids for extraction fulfils these requirements because of their unique physical chemical properties and usually low toxicity. Selectivity can be achieved by suitable selection of pressure (density), temperature and modi fier conditions which enable solvating power to be varied. The high diffusivity of supercritical fluids provides rapid sample penetration and extraction. Use of fluids with low critical temperatures enables extraction to be conducted under mild thermal conditions ensuring that thermally labile compounds do not decompose. The technique can be used off-line, and the extracts analysed by appropriate techniques, or it can be used on-line, by coupling with a variety of chromatographic techniques. These can then, if necessary, be coupled fur ther with spectroscopic techniques, such as Fourier transform infrared, ultra violet or mass spectrometry, to provide specific identification or structural information.

Klappentext

This book discusses the recent developments which will lead to the routine use of supercritical fluid in analytical extensive chemistry. Individual chapters, written by authorities in their fields, contain the maximum of practical advice in addition to covering appropriate theoretical detail.

Inhalt
1 Introduction to supercritical fluid extraction in analytical science.- 1.1 Introduction.- 1.2 Extraction controlled by diffusion out of the matrix.- 1.3 Equations for discontinuous extraction.- 1.4 Extraction controlled by both solubility and diffusion.- 1.5 Solubilities in supercritical fluids.- References.- 2 Methodology for off-line supercritical fluid extraction.- 2.1 Introduction.- 2.2 The off-line SFE experiment.- 2.3 Instrumental considerations.- 2.4 Supercritical fluids and modifiers.- 2.5 Developing an off-line SFE method.- 2.6 New directions in off-line analytical SFE.- 2.7 Summary.- References.- 3 Coupled (on-line) supercritical fluid extraction-gas chromatography.- 3.1 Introduction.- 3.2 Generalized approaches to SFE-GC coupling.- 3.3 Performing direct injection on-line SFE-GC.- 3.4 Summary.- References.- 4 Coupled supercritical fluid extraction-capillary supercritical fluid chromatography.- 4.1 Introduction.- 4.2 Samples for which SFE-CSFC is applicable.- 4.3 Influence of the sample matrix.- 4.4 Instrumentation.- 4.5 Trapping procedures.- 4.6 Optimization of conditions for SFE-CSFC.- 4.7 Selected applications of SFE-CSFC.- 4.8 Conclusions.- References.- 5 Supercritical fluid extraction coupled to packed column supercritical fluid chromatography.- 5.1 Introduction.- 5.2 Packed vs. capillary columns.- 5.3 SFE coupled to packed column SFC.- 5.4 Instrumental aspects.- 5.5 Applications.- 5.6 Future prospects.- References.- 6 Supercritical fluid extraction-high performance liquid chromatography: on-line and off-line strategies.- 6.1 Introduction.- 6.2 On-line studies.- 6.3 Off-line studies.- 6.4 Conclusions.- References.