by
tlahren » Fri Nov 18, 2011 5:02 pm
dibenzo-pyrenes are very heavy, non-volatile and non-polar. You may just need to use more solvent in the clean-up step to elute them or try Silica gel clean-up. But Florisil should work. I don't believe I have ever seen recovery info or clean-up procedures for PAHs this large. I think you will have to fine-tune the clean-up method a little to get these compounds. Silica gel should work as well though. I use it for PCBs and PBDEs which are far heavier and non-polar than these PAHs. I know Honeywell has a method for silica gel for PAHs. It's older but if you start adding a little more elution solvent you might get these heavier compounds to come off.
http://www.honeywell.com/sites/servlet/ ... 7585100B5A
Try this method (or your own) and fractionate a spiked blank extract in 2.5 or 5mL increments through a silica gel column. Analyze each fraction to figure out how much solvent you need for elution of these other compounds.
I just thought of something... We use Acid Silica gel for PCBs etc. as it oxidizes lipids etc. and prevents them from eluting at all through the silica gel column. You might want to try like 0.5g Acid (H2SO4) silica gel followed by 0.5g of deactivated silica gel. I don't believe the acid step will affect your PAHs but I'm not sure. It would probably remove most of the edible oil matrix without a lot of worry of eluting it with your PAHs.
Just some ideas.
Ty
