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  PROCESSING YOUR DATA
 

Operations on the NMR spectrum.

To access help with a specific NUTS operation, click here.
   
Peak integration
The areas of the peaks in an NMR spectrum can often be used to compare the relative numbers of nuclei contributing to those peaks. The areas are determined by numerical integration, a mathematical procedure in which complex areas are divided up into smaller parts, which are then summed. When defining integrals, it is important to select the starting and stopping points carefully. The integration limits should include some of the surrounding baseline, rather than sitting on the peak of interest. If peaks are not baseline-resolved, it is not possible to choose two proper integration limits. In such cases, the limit should be placed at the minimum point between the overlapping peaks.
   
  To integrate peaks in NUTS, type id in the command line of the Base Level. You will see a light gray line extending across the spectrum; this is the total integral trace. This is illustrated below (click here for a larger version):
 
   
  To change the vertical size (y scale) of the integral trace, adjust the small scroll bar on the left side of the screen (the arrows are easier to use than the slider). As can be seen below, this does not affect the scale of the spectrum itself. Put your mouse cursor over the image below to see a demonstration of this (click here for a larger version):
 
   
  To define an integral for a particular peak (called a subintegral), double-click to the left of the peak, then single-click to the right. Repeat for any other peaks of interest. Your result will be a spectrum similar to that illustrated below (click here for a larger version):
 
   
  To delete an integral, position the cursor over that trace, left-click, and press d while holding the mouse button down. To see this in action, place your mouse over the image below (click here for a larger illustration):
 
   
 

Inspect the baselines on either side of your subintegrals (you may need to increase the y scale to do this). Are they flat, or do they look like the baselines below (click here for a larger version)? If they are tilted or curved, make sure that you have performed a baseline correction (bc) on your transformed data. If you have, but your integral baselines are still unacceptable, you should ask for help below, as these artifacts will cause errors in your integrations if left uncorrected.
 
 
   
 

To set the area of one peak equal to a specific number, left-click on that peak's subintegral and type v while holding the mouse button down. Enter the value you want. Click OK, and you will see the relative peak areas for all the subintegrals you defined. Your choice of integral reference can make spectral interpretation much more straightforward. In the example below, say that the triplet around 3.2 ppm is known to be due to a methyl group. If its integral value is set to 3 (the number of hydrogens in CH3), then the number of protons represented by each peak can be read directly. Move your mouse over the image below to see this process occur (click here for a larger version).

 
   
  When you are done, hit enter to return to the Base Level. To view the integrals in the Base Level, type CTRL-i; this toggles the display on and off.