V. Integration - II

Continuing from Integration - I

4. The spectrum should have a S/N of atleast 250:1 for the smallest peak to be integrated. The S/N measured for the quartet in Figure V-3, is 213, which is close to fulfilling this criterion. We can improve this number by choosing a line broadening that is approximately equal to the true (natural) linewidth of the peaks.

5. The baseline should be flat. Distortion due to phase problems should be corrected. Baseline distortion due to non-optimum parameter selection causing a baseline roll are not discussed here.

6. The peaks need to be sufficiently digitized, as discussed in Section II. If the linewidth at half-height is 1 Hz, you need a digital resolution of less than 0.5 Hz.

7. The same area should be included or excluded for all the peaks. For example, all peak integrals should be measured +/- 5 Hz around each peak, not +/- 20 Hz around one peak, +/- 10 Hz around a second peak, etc. Spinning sidebands are included in this category, and should consistently be either included or excluded.

The reason the integrals for the phenyl region is so inaccurate for the spectrum in Figures V-1 and V-2 is because the recycle time or pulse repetition time was too short. Obviously, if you did not know the phenyl region represented 5 instead of 4 protons, you could draw an erroneous conclusion about the structure of this compound from the integrals in Figures V-1 and V-2.