Chromatography Forum

Hi All,
I have looked around at literature and found that the florisil clean-up is performed on many food extracts prior to analysis by GC-ECD and sometimes GC-MS.
Nowhere have I found what types of compound it "traps" out.
Please can anyone point me to what these compounds might be?
Thanks
WK

florisil is magnesium silicate. The trapping is essentially "normal-phase" chromatography. It will tend to trap polar compounds.

WK,

Florisil is(was) made by the Floridin Company (sorry, I don't have an address) and is distributed by several vendors. Fisher published a Florisil applications bibliography many years ago which may still be available if you contact them.

Thanks for the reply, Tom.
Thats not very useful for reducing the terpene content of a sample by passing the sample through and collecting.
Aren't some of the pesticides quite polar too?
Are the columns used to trap polars and then they are eluted with a polar solvent?
WK

While a polar solvent would clean them up, I suspect that for food applications, a more disposable approach would be preferred.

It's all similar to SPE...

If I remember, Florisil is specified in quite a few EPA methods for the determination of pesticides. I think it is just an alternative normal phase to silica column chromatography and gives somewhat different selectivities to silica. In other words there are some groups of compounds which are separable on Florisil which are not so well separated on silica. I think there are some complex cleanup procedures which involve first a fractionation on a silica column followed by a Florisil column.

One of the uses of Florisil is I believe to separate PCBs from chlorinated pesticides in a pre-fractionation stage to avoid their co-elution by GC. Both are complex groups of compounds which could overlap, so an initial LC step is beneficial.

I'm sorry I can't say exactly which compounds are likely to be preferentially retained on each.

A good discussion of florisil cleanup can be found in SW-846 Method 3620B or EPA Method 608

Method 3620B
http://www.epa.gov/epaoswer/hazwaste/test/3_series.htm

Method 608
http://www.nemi.gov/

Hope this helps.

Jack