Gas Chromatography GC

Gas Chromatography (GC) can be performed in the indirect and direct mode, having the advantages of high efficiency, sensitivity, speed of separation, and ability to separate analytes from impurities. The indirect mode requires the derivatization of the chiral compound with an optical pure reagent, resulting in diastereoisomers that are then separated on an achiral stationary phase. The direct mode is performed with a CSP. GC has the great advantage of not needing optimization of mobile phase concerning solvents, pH, modifiers and gradients (Eljarrat et al. 2008). However, there are only a few chiral columns that can be used in GC, which limits the application of this technique. The most used columns are cyclodextrin-based and have demonstrated a great applicability in organochlorine pesticides (Wong and Garrison 2000; Eljarrat et al. 2008). Another useful CSP are based on metal complexes such as metal-b-diketonate polymers (Rykowska and Wasiak 2009). One disadvantage of GC is the need of derivatization, in some cases, to increase the volatility, to prevent the peak tailing and thus to improve detection limits by the peak shaping (Zhang et al. 2009). The high temperature used in GC is a drawback when the analytes are not volatile and when the chiral compound can suffer racemization or decomposition (Schurig 2001; Jiang and Schurig 2008) ; Thus GC has several limitations to environmental analyses of chiral pharmaceuticals (Huggett et al. 2003; Lamas et al. 2004; Jones et al. 2007).

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