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water vapor. The technique was extended to soft glass by Ogan et al. [6] who also developed a stable
flexible soft glass tubing [7,8] that required no external polyimide coating. This was achieved by a
careful annealing procedure immediately after drawing. It appears that flexible fused silica tubing has
also been constructed without a polyimide coating [9]. Capillary columns can be fabricated having
diameters between 50 and 1000 µm and lengths between 10 and 500 m. The film of stationary phase,
usually between 0.1 and 1.0 µm thick, can be formed by either passing a solution of the stationary phase
through the column and subsequently evaporating the solvent from the surface film so produced, or the
stationary phase can be deposited by direct surface polymerization.
The injection of a sample onto a capillary column is far more difficult than placing it on a packed
column. This is because the loading capacity of the capillary column is one to two orders of magnitude
less than that of the packed column. Consequently, the sample size must be proportionally reduced and
this renders on-column injection impractical for the smaller-bore high-efficiency columns. The reduced
sample size is achieved by means of a split flow injection system as shown diagramatically in Figure
1.3.
Figure 1.3
A Split Flow Injection System
