Hello Everyone,
I was wondering if it is feasible to measure the desorbed Phosphate after extraction with 31P NMR.
in details:
Objective: detecting the desorbed P qualitatively!
Part 1: conventional soil P desorption:
P desorption with citric acid for 24 hours, shaking, and filtering. So I have a clear solution containing desorbed P. This solution will be used later for NMR 31P.
Part 2: NMR preparation and regarding uncertainties:
- Should I also prepare NaOH+EDTA extraction with the solution from part 1?
- If it is a must with NaOH+EDTA: Will NaOH be neutralized wiz citric acid? (cuz the solution may contain citric acid)
- If it is not necessary with NaOH+EDTA, may I know why? (I guess, cuz P is already released in the solution by citric acid?)
- last but not least, the sample may contain high Fe and Ca.....
Thank you so much for the answers.
I googled all possible keywords, but there are no relevant papers.
I do appreciate it!!!
You can certainly measure desorbed phosphates with 31P NMR. Depending on phosphates' concetrations you may need concentrate your extraction or collect longer time 31P NMR.
pH will only affect 31P chemical shifts. Adjusting pH to neutral may help to identify phospahte species even for inorganic phosphate. EDTA is preferred since metal ions can broaden 31P peaks. Depending on ion concetrations, 20-200 mM EDTA in final solution can be used to titrate out the best concentration to be used. T1s and T2s of phospahte peaks should be used to quantify phosphates in extraction.
Xia Ge Thank you so much for the details!! there, I still have some further questions, may I continue asking?
- based on how I understood your reply and the purpose of NaOH in NMR, It is feasible to skip the NaOH extraction, and directly use the extracted P-contained solution?
- However, it is suggested to add EDTA into the solution for chelating metal ions therein, reducing the disturbs on P-peaks. (but citric acid has already chelated metal ions...)
Last but not least, may I know some papers (published) on this topic? cuz I have googled throughout, but I did not find an exact paper regarding this topic or study field.
I may also use the wrong keyword, cuz I am quite new to NMR (I never used it before)
appreciate it!!!!!
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