I got some great comments from Tony and Gary on the “Dealing with a Mixture…” post that I decided to do a follow-up post. http://acdlabs.typepad.com/elucidation/2008/02/dealing-with-a.html
In my lab days, I would routinely workup a newly acquired 1H NMR for an unknown sample prior to acquiring a 2D NMR dataset. One of my goals was to examine the integrals from the 1H NMR spectrum. Based on the integral ratios, I could quickly determine, although not with complete certainty, which signals did not belong to the compound of interest.
From the 1H NMR shown below, making a general assumption that the doublet at 0.83 ppm belongs to a single CH3 group, the multiplets at 1.06 and 1.17 ppm can be classified as not belonging to the compound of interest.