Timeline for Just looking for some help with finding relative ratios of components in a mixture using proton NMR
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
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| Sep 19, 2021 at 18:15 | answer | added | Buttonwood | timeline score: 0 | |
| Sep 19, 2021 at 3:31 | comment | added | 10ppb | The polarization of the different protons in your molecules will relax back to equilibrium at different rates. The recovery time has to be long enough so that even the slowest relaxing signals have equilibrated to the desired degree. This typically means 5 to 10 times the longest T1. There are are several other precautions needed to get accurate integral ratios. Here is a brief guide to qNMR: enfsi.eu/wp-content/uploads/2017/06/… | |
| Sep 18, 2021 at 17:44 | answer | added | Karsten♦ | timeline score: 2 | |
| Sep 18, 2021 at 14:22 | comment | added | orthocresol | @Archimedes_Eureka My real suggestion re: your duplicated accounts, would be to repost your question with the account which you have a login for. There's not much information you're losing by doing so. I can delete this one. Re: the actual question: speak to somebody who does NMR at your institution about the recovery delay. You will end up needing their help anyway, if you want to rerun the spectrum. You are correct that the sensitivity of NMR is intrinsically low, but that is not an issue for the problem you're solving, it's not relevant. | |
| S Sep 18, 2021 at 13:25 | comment | added | Archimedes_Eureka | On that note, why does the integration and chemical shift change when you have a mixture? I am unfamiliar with the recovery delay part too. If anyone wouldn't mind helping me address possible deficiencies, especially the concept of why NMR is an "insensitive" technique, I'd really appreciate it. | |
| S Sep 18, 2021 at 13:25 | comment | added | Archimedes_Eureka | The mole ratio was just to be taken from any two signals, one for each compound, that corresponded to the pure spectra, but had different integration and even chemical shift in the mixture spectrum. We didn't have a standard, so I suppose that would be why using different signals will give a different mole ratio. But again, it's a relative and not an absolute measurement. | |
| Sep 18, 2021 at 10:48 | comment | added | orthocresol | Integration is never going to be perfect, there’s some error. Make sure you use a long recovery delay if you want quantitative integrals. Speak to someone if you dont know how to set that up | |
| Sep 18, 2021 at 9:39 | comment | added | Alchimista | There should be a kind of averaged MW somewhere, in reference to weight. Is the mole ratio alone more independent of the peaks you choose? | |
| S Sep 18, 2021 at 8:36 | review | First questions | |||
| Sep 18, 2021 at 9:03 | |||||
| S Sep 18, 2021 at 8:36 | history | asked | James | CC BY-SA 4.0 |