PAHs in fish tissue

[yuri]

Hi,

I'm looking for a method to determine PAHs in fish tissue, which doesn't involve GPC or HPLC.
In my Lab I have an ASE for the extraction of fish tissue and a GC-MS for the determination. The problem is the cleanup!

At the moment I just found methods which use GPC cleanup but I have not.

I know a good method for PCBs in fish tissue: extraction by ASE (with n-hexane), cleanup with concentrated sulphuric acid and GC-MS determination. However I'm afraid of cleanup: I suppose that PAHs analytes could react with sulphuric acid.

May anyone help me?

Thanks in advance

[chromatographer1]

I would suggest that you use flash chromatography for the cleanup. Using hexane as a mobile phase on normal phase silica should be a snap.

best wishes,

Rod

[Steve Reimer]

You are right to exclude conc. sulfuric acid. Some of the PAHs will be destroyed.
We have done this analysis in hundreds of fish samples. Our method includes ASE extraction followed by silica gel column cleanup. This works better for fillets than whole bodies, better for hard (subcutaneous) fat than oils. The fats elute after the PAHs and neutral organics on the silica gel.
A good first step for cleanup is to put the extracts into a freezer for a day or two. The excess fat will congeal and can be removed. The overall level of cleanup you need will depend on your required detection limits and the type of fish you are analyzing. Good luck!
The ms ion source still smells like fish afterwards!

[yuri]

Thanks a lot to all of you!
I will try silica gel cleanup.
Can you tell me something about the quantity of silica gel and the volume of n-hexane?

Thanks in advance

[Steve Reimer]

Up until a couple of years ago we hand packed glass columns with 10g of silica gel and treated the whole extract (~20g of fish representing up to 2g of fat). Now we treat a portion of the extract using a commercially available cartridge (Supelco). The volumes scale nicely so for our original 10g column we washed with pentane, added the extract in hexane and eluted with 50mL of 40% dcm in pentane. A 10g Supleco cartridge can be treated the same as our hand packed column, a 1 g would be eluted with 5mL of the elution solvent.
In our trials, fish had no interfering compounds eluting before the PAHs. The fats elute after the PAHs and the other nasty looking stuff stays on top of the column. We could get more neutral organics by elution with 100% dcm but at the cost of more lipids.
You will need to evaluate your procedure with your type of fish. The elution changes slightly with the type of fat, so beware.