Capillary Chromatography - Applications of Capillary Columns in GC Analysis 1
Applications of Capillary Columns in GC Analysis
Gas chromatographic techniques employing capillary columns have been applied to the whole gamut of industrial analyses, ranging from product control to pollution monitoring. The columns have also found use in forensic analyses and biochemical studies where the intrinsic high mass sensitivity, that can be achieved when the capillary column is used in conjunction with a high sensitivity detector, can be a considerable advantage. The high speed capability of the capillary columns also makes them particularly useful in process control and in intermittent rapid monitoring, for example, the analysis of a patients breath under anesthesia. The following examples are taken from specific applications that illustrate some of the unique advantages of the capillary column.
Chiral Separations with Cyclodextrin Stationary Phases
Until relatively recently, interest in chiral chemistry had been largely academic and occupied a relatively minor position in the analytical chemistry syllabuses of most universities. However, in the early 1980s, the commercial interest in chiral substances suddenly increased, particularly in chiral drugs, and this interest proliferated very rapidly. This new enthusiasm was fostered by the recognition that the respective physiological activity of the isomers of a drug could differ radically and this was found to be true for many physiologically active compounds and, in particular, physiologically active biotechnology products. However, the major impetus arose from the unfortunate birth defects initiated by one of the enantiomers of Thalidomide. This drug was manufactured and sold as a racemic mixture of N-phthalylglutamic acid imide. However, the desired physiologically activity was found to reside solely in the R-(+)-isomer and it was discovered, too late, that the corresponding S-(-)-enantiomer was teratogenic and could cause serious fetal malformations. The thalidomide disaster evoked the interest of all pharmaceutical manufacturers and also the drug regulatory committees. As a result, research activity in the field of stereochemistry became almost frenetic. The United States Food and Drug Administration recommended that the physiological activity of each isomer of all new drugs must be individually tested. This forced the companies concerned to investigate the problems associated with the separation of enantiomeric mixtures. The demand for enantiomerically pure drugs rose rapidly and in (1993), the world market in enantiomerically pure drugs exceeded $35 million, the majority of which were cardiovascular and antibiotic drugs. It follows, that as enantiomeric pairs are chemically almost identical, separation is very difficult, and the high efficiencies available from capillary columns became essential for their rapid separation.