Hi all,
I am analyzing the concentration of PFOA (Perfluorooctanoic acid) using LC/MS/MS (negative ionization mode). In my method, I'm also using 13C8-PFOA as my internal standard (IS) to take in account of any interference that might occur during my sample prep. My sample matrix contains 0.5 M Na2SO4, and I am experiencing a weird phenomenon- I suspect the high salt content has caused this issue. Although, I've using the diverting valve to elute out the salt in the early stage in my method.
The peak areas (PA) of the IS in my samples have similar intensities to my standard samples. However, the PA of the PFOA in my samples are suppressed by at least 10 folds compared to my standard solutions- I know this because I've estimated the PFOA concentration range in my samples. From my understanding, the PA intensity of IS will experience the same/similar degree of interference from sample matrix compared to the target analyte (PFOA). However, this wasn't the case in my experiment. Have anyone experienced this before? If so, do you have any suggestion to fix the issue?
Many thanks!
Ted
Dear Thien,
I hope this article (attached) will help you.
Best wishes
There are many compounds listed as PFOA. To use the IS effectively, your IS must match the native standard as much as possible and the difference will be just the Carbon13 specific condition. This way, the retention of the native and the IS will be "exactly the same" and will have the same matrix effect. Did you use the correct IS? IS is very expensive and you may not be able to match all of the IS to all of the native PFOA. I would guess that you may use the wrong IS. Prove me wrong and tell me what is the retention time of your target PFOA and the IS.
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