Hi all,
I'm planning to analyze for PFOA using LC/MS/MS, however, my solution is containing 0.5M Na2SO4- someone told me it can interfere with the ionization process of the instrument. Though, I don't want to use any ion exchange filter since it can also filter out the PFOA. I am also using internal standard addition in my analysis, and I think this can correct any interference from the salt. Another colleague of mine said with a small injection volume (10 uL) in my protocol, the mobile phase will be able to dilute the salt content to the point its effects will be negligible.
Thus, is it possible to inject 10 uL of 0.5M Na2SO4 solution to analyze for PFOA using LC/MS/MS without additional separation step prior to the analysis? I want to hear more opinions from other experts for this. Please let me know your thought/experience.
Thanks!
I'm assuming you are doing a reverse-phase analytical separation? In which case you can probably expect your salts to be un-retained on the analytical column and come out in the void volume. You could divert the first minute or so (however long before your first analyte elutes) to waste instead of to the MS
If you are so worried about the salt in the sample, get rid of it then. Passing your sample thru a C18 SPE if your sample is mainly aqueous. The salt will not be retained on the cartridge. PFOA will stay on as they are more non-polar and you can elute them later with a strong solvent of your choice. The easy way is using diverter valve to pass the the salt to waste at the beginning of the run as Katherine suggested.
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