Dear Tahani Aldhafeeri, would you please go through this RG link. My Regards

https://www.researchgate.net/figure/A-UV-visible-absorption-spectra-of-NMP-showing-absorbance-below-450-nm-increasing-with_fig1_321438196/amp

Additional information is that NMP is more susceptible to sonochemical degradation. So, care should be taken if the solution is subjected to sonication. The attached file gives additional information. My Regards

Thanks a lot Abdelkader