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Fluoride matrix effects
Posted: Mon Apr 29, 2019 9:40 pm
by Mritari
We have a Metrohm 882 running epa 300.0 and are having problems with quantifying to the expected concentrations of fluoride in certain matrices. Our QC samples (ICV, CCV, MS) consistently pass (+/-10%), but for some samples, we get ~ 50% expected recovery on certain wastewaters, and ~200% expected recovery on certain soils. Any ideas on what could be going on? We cleaned the suppressor with H2SO4/Oxalic acid but that didn't seem to help. MS/MSD of the problem samples get close to 100% recovery for fluoride which is what is confounding.
Re: Fluoride matrix effects
Posted: Thu May 02, 2019 5:10 am
by Markus Laeubli, Metrohm
Dear Mritari
Samples containing alumina or titanium (as examples) may show low fluoride concentration by IC due to absorption. Only free fluoride is detected.
A too high response is more difficult to explain. Short chain organic acids might interfere.
Do not hesitate to send me chromatograms (*.idet) with details of the procedure (
markus.laeubli@metrohm.com).
Re: Fluoride matrix effects
Posted: Mon Jun 17, 2019 7:48 pm
by James_Ball
I think Acetate can elute near Fluoride, depending on the column and eluent being used.
Re: Fluoride matrix effects
Posted: Fri Jun 21, 2019 8:51 pm
by anionman
Acetate is very close and will co-elute. If the F level is high enough the acetate peak will add to the F peak and may not show up as even a bump in the peak. That might explain a high recovery, but not a low one. Running a high dilution of samples allows you to see if there is any co-eluting acetate. My F recovery on high level F decreases as my column ages. It only calibrates well up to 4 ppm when it's old. When new it works well up to 8 ppm. I would try dilutions.