C18 SPE cartridges can be useful for purification of small hydrophobic molecules from a solution that also contains proteins, buffers and salts. As far as I can tell, they can also be used for the opposite, i.e. to remove the small molecules from solution by retaining them on the column bed.
The common cartridges (e.g. Thermo HyperSep C18 SPE cartridge) are designed to be used by connecting them to a vacuum chamber and thus pulling the liquid through them.
I wonder if anyone has tried to use these simply by pushing the liquid through using a syringe plunger?
And if so, do they come in standard sizes so normal 1 mL / 2 mL / 5 mL / 10 mL syringe plungers would fit?
I never used them this way. However, adapters seem to be available for this purpose.
https://www.sigmaaldrich.com/catalog/product/supelco/57020u?
https://www.bgb-info.com/home.php?cat=29455
Yes, it is possible to apply positive pressure to the top of an extration column, and adaptors are available. For some applications we have used centrifugation to apply the force. It must be a swing-out rotor of course. This allowed us to collect eleuent directly into aurosampler vials.
Hurst PR, Whelpton R. Solid phase extraction for an improved assay of physostigmine in biological fluids. Biomedical chromatography : BMC. 1989; 3: 226-32.
To some extent it depends on how many samples need to be processed.
vacuum manifolds can be a problem if some cartridges have much slower flow rates than other. Simple manifolds, for just a few columns can be constructed from 3-way luer taps.
Oded, if your questions, is Can I take a the punger from a syringe and use that?, then yes you might find a punger to fit, but if you want to apply several solutions, it is highly likely that withdrawing the the plunger will disturb the column bed. The adaptors for use with a syringe allow for the pressure to equilibrate and then they can be removed.
We have an auto prep station that uses positive pressure to push the sample through the resin. I can't recommend it because it is not compatible with our matrix. That said I would think that if you were to find a syringe plunger that would fit the cartridge barrel your results would be poor. The rate at which the sample flows over the resin is very important and variance between the rates would result in variance in the amount of material retained.
Yes, controlling flow rate through columns can be critical. Sometimes retention can be inproved by diluting the sample - for example by 10 fold.
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