A major infant formula manufacturer was forced to recall supplies from Australian supermarkets after their dry milk product was found to contain hazardous nanocrystals of Fluoride doped Hydroxyapatite.
I am currently most interested in the formation of covalently bound Fluoride attached to protein, heme centres and especially Phosphorus in food.
I have not found any literature with data for 19F NMR of milk samples containing Fluoride, either as a result of pollution, or the deliberate addition, as occurs in some human experimental locations in the UK or South America.
If anyone has access to NMR facilities, this could make the basis of a refereed paper reporting results of incremental addition of Fluoride to milk and measuring the effects of high temperature treatment as occurs in pasteurization.
31P NMR looking for 19F coupling could also prove useful.
Would anyone like to collaborate?
I can highly recommend Dr. Michael Kovermann of the University of Konstanz.
His research interests contain (among others) 3D-NMR techniques to ascertain protein structures as well as research and development towards high-resolution 19F-NMR spectroscopy of proteins:
https://www.chemie.uni-konstanz.de/en/research/groups/gr-kovermann/
Fluorine present in traces in hydroxyapatite (also in traces) may be very hard to detect not only because of the small quantities but also because it is probably in the form of CaF2 and both substances are solid. Btw, it may be present as a natural trace element in the hydroxyapatite; it always accompanies calcium in minerals.
Long time ago I was after detecting (by NMR) residual fluorine in processesed gypsum (that's how all fluorine for teflon etc is obtained: extracting it from natural gypsum; some deposits contain up to 1% of it; after extraction it drops to 0.1% or so). That was actually a task more suitable for low-resolution NMR - there was a nice Pyke doublet, with the FID lasting just some 20 microseconds. I would expect something similar also in this case (though one never knoes, of course, until one tries).
Dear Dr. Geoff Pain
I am very interesting in your ideas about milk and fluoride interactions . I hope that we can do so work together.
Many thanks to you all for the very helpful comments. I agree solid state NMR might assist greatly in any new experiments.
Hmmm, I am not sure solid state NMR will help. What is understood today by "solid state NMR" is a technique involving magic angle spinning and cross-polarization. It is suitable for 13C studies and allows molecular structure studies without dissolving the sample. It is not a trace analysis technique, and it is not suitable for measuring traces of mineralized 19F.
When I said that the fluorine traces in hydroxyapatite are probably solid and that I was detecting concentrations of 0.1% of CaF2 (not really "traces") in processed gypsum, I was not recommending the use of "solid state NMR" (that would be useless). I meant old-fashined, direct "NMR of solids", a very different thing , with broad-band, short dead-time probes. Not a routine NMR spectroscopy stuff.
You should also consider another option: a chemical transformation of the sample to convert any fluorine that it might contain into soluble species and then apply usual liquid state NMR spectroscopy. Not being a chemist, though, I am not sure whether any such chemical processing is possible (I am rather skeptical).
Also, since this problem might well be totally beyond the reach of NMR, you should think about other methodologies for the essays.
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