Two column selection

Two position valve application – 6 port valve
(Non-Java)

When two different columns are required at frequent intervals at similar oven temperatures, a 6 port valve can provide rapid selection of the one to be used.
The column not in use is protected by a blanket of inert mobile phase, and may be rapidly brought to equilibrium when required. (If flow must be maintained to the non-selected column, an 8 or 10 port valve is necessary.)

Further reference

More applications with two position valves
Valco injectors and valves
Cheminert injectors and valves