Preparative chromatography alternative techniques

Generally SFE has proved a greater success than SFC. However, the need for successful automation is a significant restriction in many routine applications. SFE has been promoted as the ideal technique for sample preparation for chromatography. Meanwhile it is clear that this is far too optimistic [77,292]. As shown in Section 3.4.2.7, SFE does not guarantee quantitative analysis. Before any technique can be fully accepted, it should be capable of generating reproducible results. This is clearly not the case in SFE. Also, sample sizes of (on-line) SFE tend to be much smaller than in other methods, such as MAE or ASE (Table 3.4), which raises the risk of nonrepresentative sampling. There is a need for SFE to be carried out on reference materials of known composition determined by an alternative technique. 

High-performance liquid chromatography (HPLC) techniques offer versatility with minimal sample preparation. Its specificity and sensitivity, relatively small sample requirements, and the ease of operation make HPLC a practical alternative to GLC. HPLC has also been adapted to the simultaneous quantification of a large variety of drugs and... 

Since the first separation of enantiomers by SMB chromatography, described in 1992 [95], the technique has been shown to be a perfect alternative for preparative chiral resolutions [10, 21, 96, 97]. Although the initial investment in the instrumentation is quite high - and often prohibitive for small companies - the savings in solvent consumption and human power, as well as the increase in productivity, result in reduced production costs [21, 94, 98]. Therefore, the technique would be specially suitable when large-scale productions (>100 g) of pure enantiomers are needed. Despite the fact that SMB can produce enantiomers at very high enantiomeric excesses, it is sometimes convenient to couple it with another separation... 

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