Dear Roya, I agree that factors such as resolution, pulse calibration, delay and temperature of analysis are important factors for greater accuracy in a quantitative NMR analysis. In most NMR devices and spectral processing software, like MestreNova, the method used to calculate the integration is the Riemann method with a margin of error of 4 to 6%. I am sending you an article that can help answer your questions. The article talks about basic principles about acquisition and processing parameters, including integration. My Best Regards.

Dear Roya, indeed in order to take more quantitative information from an NMR spectrum, several factors need to be taken in account. So from what I understand you only receive the spectrum printed and already integrated by an external operator, right?

Usually, the integration is reliable if it is done properly and if the sample does not contain protonated solvents. There are however some factors that may play a role. One of them is the presence of a considerable ammount of protonated solvent in solution that can saturate the detector and in this way, affect the integration of the signals. Another possibility is the poor shim, but if you see well the multiplicity of signals, this should not affect that much. Another possibility is the fact that certain atoms may undergo through an hydrogen-deuterium exchange with the solvent, but this seems unlikely for alkenes. Then you need to look at the baseline of the processed spectrum. If it is not straight, this may affect the integration. Finally, the integration can be affected if the ammount of compound/number of scans are low and you are working with a low S/N ratio. If you rulled out all these factors, then you can trust the integration. Of course, I've listed only the factors that you can control with a spectrum that you did not record, because regarding others like the recycle delay (that you've mentioned), you cannot unfortunately do soemthing about it :(

If you are sure of all the factors listed above, then you should expect an error of integration of 20% maximum.

Hope I could help :)

Dear João, thank you for taking time out to answer my question. I appreciate the informations you have shared.

Best Regards,

Roya

Most of the time standard parameters used for 1H NMR measurements are good enough to make integration reliable, certainly reliable enough for the purposes of structure determination (or confirmation). Typical integration error is well within 10% or even less, like mentioned in the previous reply. This is, of course, assuming that the instrument is in good conditions and there are no gross operator errors.

The exception would be the case of exchangeable protons, but since alkene protons are not, you may consider the possibility that your anticipated structure might not be what you expect.

Another issue influencing NMR spectra is the presence of tautomeric forms or slow intermolecular rotation, which brings extra signals and disturbs everything, including integration - but this is an entirely different story.

Thanks a lot dear Vladimir!

Dear Roya, I agree that factors such as resolution, pulse calibration, delay and temperature of analysis are important factors for greater accuracy in a quantitative NMR analysis. In most NMR devices and spectral processing software, like MestreNova, the method used to calculate the integration is the Riemann method with a margin of error of 4 to 6%. I am sending you an article that can help answer your questions. The article talks about basic principles about acquisition and processing parameters, including integration. My Best Regards.

Thank you so much dear Eduardo for your helpful article.

Best Wishes.