Chemical shift pertubation in 1D spectra

Analysis Version 3
1

Hi,
I am doing a pH titration using 1D 1H and 1D 13C spectra. I was following the CSP-Tutorial but did not get a meaningful result. Is it possible to use the chemical shift pertubation tool with 1D spectra? In the first place I just want to see the plots CS vs pH for each NMRatom. A pka fitting would also be nice but this I can also do in another program.
Thanks and best wishes Johanna

2

Hi Johanna,

I had a go at this with some 1D spectra just now and it worked nicely with some concentration dependent data.
What I noticed when trying to turn it into pH-based data was the following:

  1. if I try not to do a fitting and use “blank” instead, I get an error - this is clearly something we need to look into
  2. if I simply do the normal fitting anyway, the fit is (obviously) really bad (as I’m using the wrong equation for the data), and the graph seems to focus in on the fit which means I only one value and it looks like there is something wrong with the graph. But by zooming out, I can see all values again. Above the graph you can switch off showing the fit (and error), so then you simply see the raw data.

In terms of doing a pKa fitting: that’s obviously a matter of entering the right equation. I think if you give @LucaM an equation he should be able to add it relatively easily (or tell you how you can add it). Or simply export the data from your results DataTable to another program.

I hope this helps.

Vicky

3

Dear Vicky,
thank you very much for the quick and helpful reply. Now I can see my data and export it.
For getting the pka from the changes in chemical shift I use euqation 15a from this paper: https://doi.org/10.1002%2Fmrm.1910360505
If there is a way to do this fit directly in CCPN, this would be great.
Best wishes
Johanna