Solventless injector

Figure 6.12 Schematic diagram of a solventless injector used for packed column SFC. (Reproduced with permission from ref. 132. Copyright Dr. Alfred Huethig Publishers).

Major applications of SFE-SFC are somewhat limited at the moment to the analysis of lipids and pesticides from foods and similar matrices and different types of additives used in the production of polymers [79,146,188-194]. The approaches used cover a wide range of sophistication and automation from comprehensive commercial systems to simple laboratory constructed devices based on the solventless injector [172,174,175,188]. Samples usually consist of solid matrices or liquids supported on an inert carrier matrix. Aqueous solutions are often analyzed after solid-phase extraction (SPE-SFE-SFC) to minimize problems with frozen water in the interface [178,190]. The small number of contemporary applications of SFE-SFC reflects a lack of confidence in supercritical fluid chromatography as a separation technique and competition for... 

Compared with the samples typically separated by supercritical fluid chromatography most solvents are significantly more volatile and can be removed from the sample by evaporation in a short open tube or packed precolumn [174-178]. Solventless injection requires only minor modification to a standard rotary injector, either addition of a second valve or tee piece and a precolumn. This allows sequential programming of the independent processes of solvent removal and sample deposition in the precolumn followed by dissolution of the sample in the mobile phase and its transport to the column for refocusing. Quite large solvent volumes (hundreds of p,l) can be handled in this way, but typically smaller volumes are used. The only real limitation to solventless injection is that the volatility difference between the sample and solvent must be sufficient for effective removal of the solvent without loss of sample. In addition, effective sample focusing at the head of the column is required to maintain an acceptable separation... 

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