ANALYZING YOUR SPECTRUM
   
  Help! My integral baselines are not flat!
 

This problem is caused by a spectrum baseline that is either sloping across the spectrum, or has some curvature to it. Make sure that you have performed a baseline correction (bc) operation on your data after the Fourier Transform, but before you set a chemical-shift reference, do a peak pick, or attempt integration.

If you have performed a baseline correction, but your integral baselines are still not flat, they must be processed further. You will make both zero-order (linear) and first-order (curved) adjustments. Enter this routine from the Integral level of NUTS (type id if you are not already there) by typing b. You will notice that your preset integration limits will be ignored. Do not be concerned; they will return when the correction routine is done.

In practice, it is easier to make the first-order correction first. Move the mouse to the right and/or left while holding down the right button to remove any curvature in the integral trace. Do not worry if the baseline slopes linearly across the peak; this will be corrected in the next step. The images below show an example. Move your mouse over the figure to see the effect of a first-order correction (click here for larger pictures).
 
  Note that, after this first adjustment, the integral tilts in the other direction; however, neither side has any residual curvature.
 
  Now left-click and move the mouse to the right and/or left to straighten out the linear slope, as the figures below demonstrate when the mouse is placed in the image area (click here to see larger screens):
 
  Note that both side of the integral become straight and flat when the corrections are complete. If your baselines are not yet acceptable, simply repeat the procedure, starting with the first-order correction. Integral baseline correction takes some practice; it is not uncommon to go through several cycles in this process.
   
 

Hit enter to exit the integral baseline correction routine. At this point, your predefined integration limits will be displayed again, along with a corrected integral value, as shown below (click here for a larger version):