by
Rndirk » Tue Apr 16, 2019 7:39 am
How does the liner looks like after injecting a couple of those samples? You might be losing a lot of sensitivity during the very first injection already. I think that diluting an oil only 4 times, injecting it in GCMS and looking at ppb levels of pesticides is not a very robust analysis. There is plenty of stuff in this matrix that isn't volatile and provides dirty spots for your analytes to stick to.
If you want to look at a cleaner approach, but still relatively simple, there are quechers methodes for pesticides in oil/fat samples. The trick is here to find the right disperse SPE medium, to extract as much as possible matrix from the extracts, without comprimising the recovery of the analytes.
Here's an example application note.
Alternatively, sample preparation protocols based on size exclusion can yield very clean extracts of fatty samples. This requires a GPC setup though.