Chromatography Forum

Just received a caulk sample for PCB analysis via GC/ECD.

Any suggestions on an extraction method? With soil samples we use hexane, but I don't think that's going to work with the caulk. I'm also not exactly sure what kind of caulk it is, its grey so Im thinking its not just silicone.

With especially dirty soil samples we'll clean up the sample using sulphuric acid, copper and florisil, but that doesnt seem like such a great idea for the caulk samples.

Is it hard? If so, can you grind it? If you can turn it into a powder, extract with hexane like a soil and try your usual clean-up.

The sample was very gummy, it almost looked like it came straight out of a caulk gun. After the addition of hexane the caulk was still very thick. I tried to process it like a soil, but when doing the cleanup I added a small amount of sulphuric acid, a considerable amount of gas was produced which caused the caulk to expand and foam. I think the extraction and cleanup will have to be modified. I believe the caulk is either acrylic or polyurethane based neither of which I have experience working with.

Can you cool it to make it brittle? It may help putting it in the freezer and seeing if it hardens enough that you could pulverize it. Not too sure if that would help with the swelling.

Another option is to dissolve it just enough THF to get into solution. Bind the solution in enough sodium sulfate to create a free flowing solid. Add hexane and extract. The monomers should not go into solution with the hexane, only non polars like PCBs.

If the sulfuric acid breaks up the polymer then you can start with that before extracting with hexane and doing a Florisil cleanup. This can work if the resulting monomers/oligomers aren't soluble in hexane.
I have had success with this on paint samples but I haven't tried it with bulk caulking before.
If the caulk had PCBs in it as part of the formulation there will be a lot of it.

Break it up best you can and perform Soxlet 3540C extraction.

Only use hexane or you will get much more than PCBs in your extract. Follow with standard Florisil Clean-up.

Also, we do usually perform sulphuric acid cleanup otherwise you ECD will be loaded with Matrix/Organics interference..

I was able to freeze the caulk enough to make it brittle and was able to do the hexane extraction, and florisil clean up. Thanks for all the suggestions.