F

2[2SxI2]I3sin©cos2© )1-2 > 2[Sy]I3sin©cos2© 2Sy I3 sin ©cos2© 1/(2/(H(3 > -Sx sin©cos2©

When we combine this with the other two identical terms that come from I2 and I3, we have -Sx [3sin©cos2©], so we can say that the intensity of in-phase 13C coherence in the FID is edited by the factor 3sin©cos2©, which works out to 1.060, 0, and 1.060 for DEPT-45, DEPT-90, and DEPT-135, respectively.

This analysis assumes that both the 13C peak and the 1H peak are on-resonance with respect to their reference frequencies (pulse frequencies), but we tried to show at least conceptually how this is not important because all chemical shift evolution, 1H or 13 C, is refocused by the two overlapping spin echoes. The result of this analysis is that the observable (i.e., SQC) magnetization at the beginning of the FID will be

CH group: -Sx [sin©] CH2 group: —Sx [2sin©cos©] CH3 group: -Sx [3sin©cos2©]

These editing factors are the same we observe for the refocused INEPT experiment, if we replace © with n/A, where A is variable refocusing delay.

Further Reading

1. Hennel JW, Klinowski J. Fundamentals of NMR. Longman Scientific and Technical; 1993.

2. Shaw D. Fourier Transform NMR Spectroscopy. 2nd ed. Elsevier; 1984.

3. Shriver J. Product operators and coherence transfer in multiple-pulse NMR experiments. Concepts Magn. Reson. 1992;4:1-33.

4. S0rensen OW, Eich GW, Levitt MH, Bodenhausen G, Ernst RR. Product operator formalism for the description of NMR pulse experiments. Prog. NMR Spectrosc. 1983;16:163-192.

0 0

Post a comment