[simonwei]

Hi, dear all:

I am a graduate student and I finished synthesis of a polymer containing C, H, and O only . The calculated elemental analysis is C:69.07, H:6.71, O:24.22 while the found is C:68.243, H:6.829, N:0.332. The only possible nitrogen-containing impurity is the solvent used in the synthesis, DMF. But NMR spectrum shows there is no DMF peak. I heard that NMR spectra is less accurate than elemental analysis in terms of quantitative analysis. Do you think that the absence of DMF peak in NMR doesn't mean I completely removed DMF?
Thank you very much.

Simon

[Mitch]

It is only a 1/3 of 1 percent impurity,

[The_MD]

Silly question, but is there any chance of any air got into the instrument?  It would only need to be a tiny bit.