Extra Column Dispersion - GC Capillary Columns > Page 12

The maximum sample volume for solutes eluted at different capacity ratios (e.g., k'=0 and k'=5) are included in Table 1. It is seen that the limiting sample volumes are extremely small (cf. 0.073 at k'=0 for the 100 mm column) and these are values measured at atmospheric pressure with an inlet/outlet pressure ratio (g) of 2. Consequently, the sample volume at the inlet pressure will be proportionally smaller. The large column, however, can accept more reasonable sample volumes and at k'=5 on the 300 mm column a sample volume of nearly 8 ml can be tolerated. However, as the smaller columns provide both the fastest analysis and the greatest resolution, small sample volumes must be employed. This is achieved by using split injection systems.

A diagram of a split injector is shown in figure 3.

Figure 3 The Split Injector