Contamination following Florisil cleanup

[walkerd2]

Hi,
I am currently analyzing plasma and tissue samples for a select number of PCB congeners on GC-MS in SIM mode. Our sample prep procedure involves extraction into 1:1 hexane:acetone; concentrating; cleanup by 5000 mg Alltech (Grace) Florisil SPE cartridge with 1 g of Na2SO4 and a concentration step
The SPE step consists of the following: Precondition with 12 mL of hexane, Loading of ~0.5mL sample plus 1 mL rinse and finally elution with 3 rinses of 4 mL of hexane.
This cleanup procedure resulted in a lot of noise when spiking clean samples with PCBs, and we found that the SPE was causing a significant amount of noise and interference (see the below chromatographs of a hexane blank and hexane blank ran through the SPE cartridge.) Does anyone have any recommendations on how to eliminate the noise, or different types or brands of SPE cartridges that reduce it?
Thank You

[Don Shelly]

First, you should make sure that your Florisil product arrives sealed in a clean Mylar pouch and not plastic.

Secondly, after opening your package of Florisil products, protect them from humidity and room air. Florisil will quickly absorb all sorts of compounds and moisture from your room air. It is best to store cartridges in a clean container under a blanket of clean nitrogen. Otherwise, the Florisil will quickly deactivate and cause contamination.

Don

[walkerd2]

Thanks Don,
We typically just seal the mylar pouch that they came in, and do not take any further precautions in protection them. Is there anyway to re-activate them by heating etc? Unfortunately the cartridges themselves are plastic, so heating them at high temp is definitely out of the question
Thanks again

[Don Shelly]

If there's a good way to reactivate the cartridges, I haven't found it. As you guessed, heating plastic is not a good idea. I have tried methanol and acetone, but it changes the characteristics of the Florisil.

Beware of re-sealable pouches. I have not found one that is air tight. Heat sealing is the only way to successfully re-seal Mylar that I know of.

Don

[walkerd2]

Thanks again. Looking online it seems like some manufacturers offer their cartridges pouches containing five each. Are their any manufacturers or brands you would recommend just from your experience?

[Don Shelly]

LOL! At the risk of sounding commercial, mine. UCT Enviro-Clean

Don Shelly
Enviro-Clean Product Manager
UCT

[walkerd2]

Ha it was good you mentioned that. I would be interested in talking offline about possible products that would be worth me trying.

[Don Shelly]

dshelly@unitedchem.com
1-800-541-0559 ext. 219 or 1-717-247-0896