How should I switch the solvent in my GPC column?

The first step is to check which solvent is currently in the column, having ascertained this the GPC system should then be equilibrated with this solvent prior to the column being attached. You are then ready to "solvent switch the column". Attention should be given to the swell factor of the solvent within the column, together with the swell factor of the desired solvent. Solvents fall into the swell categories 70-80%, 60%, 50% and 30%. Changes can be made directly from 70-80% to 50% or 60% swell solvents, however if a 30% swell solvent is desirable for the analysis then it is necessary to switch first to an intermediate swell solvent. In all cases care must be taken to avoid immiscible solvent mixtures. Finally, each time you solvent switch GPC columns the columns will age a little, so it is advisable to solvent switch as little as possible. Ideally sets of columns are dedicated to specific solvent systems.