Determination of Certain NMR Parameters

An attractive alternative in which spectrometer line-listing routines are u.sed is as follows. After the spectral data have been Fourier transformed and saved, the proton FID is zero filled three to four times. If np = 32K, then Fn should be set to 256 or 512K. The resulting spectral lines should then have sufficient definition for peak picking. This expectation can easily be tested by examining a known multiplet, such as a triplet or quartet. The two- or three-line spacings are, of course, identical, and their equivalence must be reflected in the line listings displayed on the monitor. No matter what technique is used, J values between spin-coupled nuclei should always be reported as identical. 

Integration. As we saw in Section 1-6, H NMR spectra are almost always recorded in such a manner that the detected signals are directly proportional to the number of protons giving rise to those signals. For most H-decoupled spectra, however, a spread of Tfs and the nuclear Overhauser effect (Section 5-4) combine to produce signals whose intensities are not proportional to the number of carbons present. 

Like shimming, there are many ways to perform integration. The following parameters of Card, Pagel, and Yang represent a general approach to obtaining precise H NMR quantitative measurements  

Increase the filter bandwidth by 500-1,000 Hz if there are signals near the edges of the spectral window. 

Take enough scans to ensure a good S/N ratio and thus smoother integrals. 

---