On Tue, 16 Apr 2019 at 23:57, Viennet, Thibault <[email protected]> wrote: > Hi Edward, > > Thank you so much for your previous answer, it has been very helpful to > interpret my data. > If I may I will bother you with another question though. > > I run consistency testing for model free analysis and even if does not look > bad (around 1.06 in my case) I was wondering if there is a way to correct for > this without going back to acquire data, checking temperature calibration, > etc. > Maybe there is an empirical way? Changing the field strength used by Relax by > a correction factor? > > What are your thoughts about this?
Hi, There are zero empirical ways to fix bad data, if that is what you really have. What you can do is book say 2 hours on the spectrometer and run mini-versions of the experiments on methanol/ethylene glycol and determine the exact temperature from the spectra. If the temperature differences between all 3 experiments is < 0.5 degrees, you should be fine. Note that if the experiments are not interleaved in any way (scan or fid interleaving), you will have the daily temperature fluctuations of the NMR hall mixed into your data. That effect is quite bad. If the temperature is significantly different between experiments (> 0.5 deg), then you cannot use the data. Or at least no one will trust your results and hence conclusions. The reason is because the dynamics of the molecule changes non-linearly with temperature. The most important factor is the impact it has on the Brownian diffusion of the molecules in the NMR tube. With > 0.5 deg, the global diffusion tensor will be significantly different between the experiments and hence you cannot use the one tensor for all input data. There is no theory in existence to deal with this. So you really need to carefully determine if your data is 'good' or 'bad'. If bad, remeasurement is unfortunately the only solution. However you should note that almost everyone remeasures at least once or twice when measuring relaxation data for the first time. NMR spectroscopists with relaxation experience will also sometimes have to remeasure bad data. Regards, Edward _______________________________________________ nmr-relax-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/nmr-relax-users
