Capillary Chromatography - Introduction
The capillary column is possibly the most effective chromatographic separating device available today. It can provide the highest efficiencies and, consequently the greatest resolution. However, although it is seen by analysts as the 'state of the art' column, in fact, due to certain sampling problems, the packed column may have the edge on the capillary column for quantitative accuracy. Nevertheless, because of its speed and high resolution, the capillary column is by far the most popular in current use in gas chromatography.
The capillary column was invented by Golay, the theory of which was presented at the 1958 Symposium on Gas Chromatography and published in 1958 (1). The efficiencies provided by the capillary columns were, at that time, startling, to say the least. It will be seen when the theory of capillary columns is considered, the plate height of a capillary column is not very different from that of the packed column, the main advantage of the capillary column being its low flow impedance. As result of its greater permeability relative to the packed column, much longer column scan be used thus, providing much higher efficiencies. In addition, because there is no multipath term (see Book 9 of this series) the optimum velocity is much higher and, thus, the longer columns do not proportionally increase the elution time. Capillary columns (with very few exceptions) are exclusively used for analytical purposes and are employed in forensic analysis, pollution studies, very widely in quality control (in virtually all areas of chemical production), biochemical evaluation and particularly in pharmaceutical testing and product monitoring. They are, indeed, an essential segment of modern analytical chemistry.