Chromatography Forum

SPE are activated by Methanol and then equilibrated by water. Then the sample is applied tio the SPE followed by washing with different solvents. Finally the substance is eluted with Methanol.

Is it necessary to control the velocity of the liquid flow or does only the volumes of the solvents, which are applied, play a role?


Is it important to measure the volumes of the washing solvents very accurate?

Flow should not matter unless you go fast enough to get turbulent flow (and even then it may not matter very much) Given that you are using vacuum or a hand syringe to move the solvent through the cartridge, don't worry about it. The volume is much more important.

Ideally, a wash solvent will be weak enough to provide essentially zero elution of the compounds of interest. In that situation, the volume is not critical, assuming that you have at least enough to completely displace the previous solvent (in other words, better to use a bit too much than too little). If in doubt, it's easy enough to do a couple of "quick-and-dirty" experiments with your system and see what happens.