Visual Guide to Simulation and Fitting

The newcomer is intimidated by the host of tools that iNMR offers; he finds it is difficult just to understand what each tool is capable of doing, and cannot choose the right one.

The reality is quite simple: there are many kinds of NMR spectra, there are different problems to solve, so there are different solutions. Give a look at your own spectrum and things will suddenly become clear.


common case

 
 
In the most common case the frequency positions of the peaks (blue labels) are enough to calculate the coupling constants (by taking the differences) and the chemical shifts (by taking the average values). Use the J Manager to automatically perform these operations and organize the results.


2nd order effects

 
 
When the difference in chemical shifts between two coupled nuclei is small, the structure of the multiplets becomes more complicated and less symmetric, because the quantic effects are no more negligible.
Create a simulation document to analyze these spins systems.


peak-picking

 
 
 
 
Some peaks are broadened by exchange phenomena. If you want to measure the rate of exchange, create a simulation document and turn on the dynamic option.


noisy spectrum

 
 
Too much noise lowers the accuracy of quantitative (concentration) measuraments. If you need a more accurate mean to measure the intensity of the peaks (more accurate than plain integration), fit the peaks with the deconvolution module.


overlapping peaks

 
 
 
 
How can you measure the individual integrals of two peaks when they overlap? Here is another good reason to use the deconvolution (or line fitting) module.


2-D multiplet

 
 
To study the shape of a peak accurately, you need many experimental points (many more points than the number of parameters that describe the shapes) and you should also know the mathematical formula of your shapes. Not always are the above conditions respected. A 2-D peak, for example, is described by very few points and its shape is neither the classical Lorentzian shape nor a Gaussian. Similar problems can be solved by the Multplet Simulator.



 
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