Capillary Chromatography - History of Capillary Columns 2
Figure 1. The Rapid Separation of the Components of a Hydrocarbon Mixture on a Nylon Capillary Column
In the same year, Desty produced a technique that would produce long lengths of small diameter soft glass tubes in the form of a coil which was a far more practical material for the construction of capillary columns. Desty invented an ingenious device that very slowly fed a section of wide, relatively thick-walled soft glass into a furnace using appropriate rollers. A second pair of rollers, operating at a much greater speed drew the small capillary tube rapidly from the furnace. The size of the capillary tube so-formed depended on the dimensions of the feed tube and the relative drawing velocities of the two rollers. The glass capillary tube formed in this way was rigid when cold and was therefore, fed through a bent stainless steel tube, heated to just soften the glass, and the tube was thus formed into a rigid coil when cold. At the time, the tubes formed in this way was considered the ideal type of capillary tube for gas chromatography. An example of the separation of the isomeric heptanes on one of these columns is shown in figure 2.