SPE: Can you precondition columns ahead of time?

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

8 posts Page 1 of 1
Hi everyone,

We're taking our SPE protocol to sea. I want to avoid shipping hazmat to Bermuda ($$$) so I'm hoping we can precondition our SPE cartridges ahead of time and avoid taking bottles of solvent with us...
here's our protocol, using Oasis HLB cartridges:
Precondition with ethyl acetate, methanol then 0.1% HCl.
Pull through seawater samples, flush with 0.1% HCl and store in freezer until back on land for elution and LCMS.
It's at this point that I realize I'm not entirely sure what the point of preconditioning is? is it just a solvent rinse or is it something more? since the last step is 0.1% HCl, which is non-hazardous and much easier to ship can I simply repeat the 0.1% HCl precondition on-board the ship and 'freshen up" the columns before I pull the samples through?

thanks

Helen
The first solvent will wash out any trapped compounds left over from processing, like phthalates or more volatile analytes that might be present in the air. The methanol removes the water immissible solvent so the aqueous sample will have better contact with the sorbent. When conditioning with the aqueous I find even using the HLB cartridges that if you let it go dry then the sample is more difficult to pull through, so when I use them I try to not let the cartridge go dry until all the water sample passes through, and leave a small layer above the frit then add the wash solution and pull that through then go to the drying step. If I let it pull all the sample through then I have to increase the vacuum quite a bit to get the wash solution to begin to flow. So you could probably do the first two steps before shipping the rest of the items without much problem.
The past is there to guide us into the future, not to dwell in.
Beside cleaning from trapped compounds, it's also about wetting the pores so you get access to the surface in there.
If you start directly with water, it doesn't want to go into the tiny pores with its hydrophobic surface (C18). Once wetted with high organic, the water will mix with organic in the pores.

So maybe you can replace your organic with one that is less problematic, thinking about ethanol or isopropanol.
If you need the ethyl acetate / MeOH to really clean it, guess this step could be done on land then take the washed columns on boat and just wet and equilibrate it with IPA and HCl 0.1% before loading your samples.

On the other side Waters just came up with the Oasis Prime HLB columns which they clame don't need to be wetted & equilibrated. Don't know if and how well it works.
Maybe you want to make a comparison with your existing protocol.
I was thinking about it more and as mentioned above about the wetting process, you could also try going through the complete prep but leave a little of the HCl in the tube, seal the tube with plugs on each end, then they are ready to go when you are on site.

You could test this in the lab prior to going out to sea.
The past is there to guide us into the future, not to dwell in.
Thanks James and Hollow, both really good info and settled my problem.

We'll precondition ahead of time and ship wet, plugged columns (0.1% HCl is not hazmat). I also now have a source of HPLC grade methanol in Bermuda that I can clean up with a few sacrificial SPE columns and use to re-wet the columns before they are used. Phew!
Thank you

Helen
I think that you need to be cautious - as well as rinsing out contaminants the first organic flushes "fluff up" the coating on the particles so that it is properly adsorbent. Holding in 100% aqueous may let the coating collapse again - this is why it is recommended to run C18 separating columns in pure aqueoues onyl very briefly if at all.

The SPE manufacturers may be able to advise.

Peter
Peter Apps
I'll go with Peter
I wouldn't keep them in HCl 0.1% for longer times. It may be possible that the aqueous will be repelled from the pores. So you'll need to wet it again with 100% organic.
If so, why do the equlibration step twice...?
Also keeping the phase at low pH and aqueous environment could lead to split of the bonded phase (C18).
So if I were you, I would clean the cartridges with whatever organic you need (EtAc) then with methanol or another alcohol. Either keep it wetted with that, or even let it dry, and close it.
just before use, re-wet it with 100% organic and then equilibrate with HCl 0.1% and loadd your samples. Keep the time between those steps as short as possible.
I don't think the Waters HLB cartridges are C18 and they are polymeric support instead of silica so those my not suffer from C18 phase collapse problems.
The past is there to guide us into the future, not to dwell in.
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