December 01, 2020, 10:10:12 PM
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Topic: 13C/12C quantitation by NMR?  (Read 140 times)

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Offline Cantacoxinha

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13C/12C quantitation by NMR?
« on: November 14, 2020, 11:01:43 AM »
Food adulteration can be determined by measuring the ratio of 2H vs. 1H atoms at the site-specific portion of an analyte. It is done by measuring both spectra and then calculating the ratio. Sometimes an additional ratio of 13C vs. 12C is determined by NMR, also to check for adulteration. What I don't understand here is:

1) how is the quantity of 12C determined, if 12C is NMR inactive?

2) how in the world is 13C quantified by NMR, if carbon spectra are decoupled and thus "unintegrable"??

I'd be grateful if somebody could explain this.

Offline Babcock_Hall

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Re: 13C/12C quantitation by NMR?
« Reply #1 on: November 14, 2020, 02:41:25 PM »
I agree that one cannot observe C-12 nuclei by NMR.  Can you propose any method, perhaps an indirect one?

Offline Corribus

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Re: 13C/12C quantitation by NMR?
« Reply #2 on: November 17, 2020, 11:45:53 AM »
You can determine the isotope ratio by nmr.

See, e.g., https://pubs.acs.org/doi/10.1021/acs.analchem.7b02473

(Pironti, et al. Anal. Chem. 2017, 89, 21, 11413)
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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