Topics - Column Switching
Column Switching Column switching
is basically a method of column selection
. The technique can be used pre-column
. In a pre-column procedure a valve switching procedure can be used to select a particular column on which to separate a particular sample (e.g. it may be used to select a polar column, a dispersive column, or an ion exchange column). Alternatively, the valve switching procedure may select a column on which to concentrate a very dilute sample from which it can be displaced onto another column. In a post-column procedure, a switching system consisting of selection valve(s) can be used to divert the column eluent from the detector to another column having different selectivity. For example, if the sample is primarily separated on an exclusion column then a group of solutes having a particular molecular size range can be diverted to a dispersive column and be separated on a basis of dispersive selectivity. The switching valves and any detector
situated between columns (e.g. to determine the switching time) must tolerate the high pressures that may develop. Column switching significantly increases the versatility of a chromatographic system. The technique can also be used in gas chromatography.