Hi everybody
I have some trouble understanding what's going on chemically behind the steps I'm doing for an extraction on foods for PFC analytes (PFOS, PFOA etc etc)
To start off the extraction, I add 8mL of 100% ACN and then sonicate it for half an hour. What does the ACN do to the analytes and why need 8ml and sonicate it for so long?
Then I centrifuge it at 4000rpm for around 12 minutes, and what am I trying to separate here? Because after I keet the supernatant, I evaporate it to near dryness which means I'm trying to get rid of the ACN (since that's the only solvent I've used so far)? why do I need to concentrate the extract and then dilute it to mL with ultrapure H20?
Then after conditioning the cartridges from SPE-WAX, I load the sample into the cartridge, and wash the cartridge with 4mL of 25mM NaOAc (pH4) Is this to recovery the analytes from the cartridge?
Then I elute with 4mL MeOH, why is that? because after this, I need to elute with 4mL 0.1%NH4OH in MeOH....so why not just use the latter one instead of eluting with just plain MeOH first?
Before putting it into the instrument, I evaporate it again before putting in int. stds. Then I use 30% ACN in H2O to dilute the extract again. Why do I do this since I already wanted to evaporate the ACN in the very beginning?
Thank u in advance!!