Question

I have a spectrum obtained from an H-NMR. The sample was very dilute in the CDCl₃ that was used, so the spectrum is very noisy. The sample was scanned multiple times, but there is still a fair amount of noise. I have integrals measured out, but I've realized that some of the peaks that were included when measuring the integrals were not relevant to the compound. Does the inclusion of these peaks detrimentally affect the other integrations? Is there a way I can remeasure the integrals to determine the integration excluding these peaks? I am not able to run another scan, nor use the program to remeasure the integrals.

Answer 1

Once you perform integration in NMR, the peak height is of all peaks are related to the standard peaks that you chose a known proton. So if you choose/include some noise in that proton, then the protons without out noise also will be affected. E.g If there are 2 peaks with 5H and 3H, but there is some noise at around 5 H peak, and you calculate it as 8 H, then the integration value of 3H will be changed to 3 x 8/5 = 4.8 H. In such case chose the proton which does not have (least) noise in the measurement as standard/known H peaks.

If you have access to the data file of that experiment, you can re-plot the NMR spectra and reintegrate the spectra by excluding the noise by using many free software available over internet.