When analysing two samples with the H-NMR I prepared the two samples the exact same way at the same time, and put them in the H-NMR to measure right after each other. When analysing the results I noticed that the TMS peaks are at different ppms for the two samples (one at -0,032, and one at -0,10.
Does anyone know the reason for this?
(the first sample is n-butanol and the second one is 1-chlorobutane with MTBE)
I suspect the reason for this the 2H resonance(s) in the solvent do not have identical resonance frequencies. The chemical environment for the solvent is different for the two samples. So, the 2H resonant frequency is different.
There is no problem.Just set TMS to be zero PPM for both samples. TMS is symmetrical and the Si electron density dominates the TMS methys’ environment. The differences in the sample chemical environments (electron density) has. negligible effect on the TMS resonant frequency.
For a number of reasons with highly concentrated samples the TMS environment could be slightly different in two samples with different chemical bonds. This is rare.
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