Extra Column Dispersion - LC Sample Valves > Page 18

Courtesy of Valco Instruments Inc.

 

Figure 7 The Construction of an Internal Loop Sample Valve

For analytical purposes sample volumes of 1 to 20 ml might be appropriate, whereas for preparative work sample volumes of up to a 100 ml or more might be necessary. The elution profile of a solute band leaving an LC sample valve is controlled largely by the geometry of the sample volume itself (i.e., whether it takes the form of an exterior tube or a groove in the spigot of the valve). However, it also depends, to some extent, on the geometry of the exit ports or unions to the valve-column connecting tube.