After QuEChERS cleaning procedure we still have a lot of fat in our samples, and it was really deadly for our GC column (HP-5MS) after 5 samples.
Can anyone tell how do you solve this problem, or what methodology do you usually use in your lab for this kind of samples. It is the first time we analyse the biological material, so I will appreciate any help.
It depends upon the pesticides that you are seeking. If they are lipophilic it is an issue and you'll probably have to move to solvent exchange followed by column chromatography cleanup. If they are significantly more soluble in the acetonitrile (polar/semipolar) then you can freeze the Quechers extract prior to dSPE and the fats will congeal out (you can physically remove them). Use a high fat dSPE cleanup, like the Supelco Z-Sep+, after you remove the fats.
The old FDA PAM manual has solvent exchange/column cleanup procedures for high fat samples. Most people don't use it anymore but all those methods still work quite well.
Thanks a lot for your answer!
We are working now with DDT, DDE, Aldrin and PCBs. So we`re dealing mostly with lipophilic pesticides.
Have you tried to use acidic cleanup?) It's really hard method and it can crash some part of your analytes, but it worked well :-)
We will try, jointly with a standard addition method, to trace the possible pesticide modification. Thank you!
We extracted DDT, DDE Aldrin and PCBs from fish tissue using Accelerated solvent extraction, then SPE but often found we still have too much lipid so we would freeze our extracts (hexanes) to remove the lipids. We found cold centrifuging helped to separate the frozen lipids from the hexane. We would use acidic cleanup when we were only testing for PCBs and PBDEs.
My experience with OCP/PCB is that the conventional cleanup techniques didn't work very well for the PCB fraction. We had some success with silver-impregnated alumina, as well as back-extraction into DMF or DMSO, but it is time-consuming and a real pain. Conventional Florisil cleanup worked well for the OCPs. I did try using isotope dilution (adding labeled analytes prior to extraction) and that worked pretty well, but it doesn't work well with PCBs.
Try this method. It will help if you have GC/QQQ because you don't need to concentrate the sample. Check with Agielnt for the EMR product to absorb fat from the QuEChERS extraction. Acetonitrile extraction would not extract fat from sample (only 1-2% of fat would go to acetonitrile (fat has poor solubility in acetonitrile). The rest of fat will be absorbed by C18 or EMR phase. Go to Google and search for Agilent Enhanced Matrix Removal
Thanks for the answers!
We now thinking about EMR after QuEChERS extraction, hope it will work well, need to try it, thank you.
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