The DEPT Experiment and Some of Its Useful Variants

The DEPT (distortionless enhancement by polarization transfer) experiment, proposed in 1982, has revolutionized NMR spectroscopy for signal assignment, particularly for obtaining information with respect to, e.g., the type (multiplicity) and the number of Cq, CH, CH2, and CH3 in the investigated molecule and for calculating corresponding carbon type-specific subspectra (spectral editing). In this chapter, we have explored various DEPT pulse sequences and have discussed how the pulse sequence elements cooperate and contribute to the final shape and appearance of the observed signals. In addition, we have compared the results with other experiments designed for the determination of multiplicities like the spin echo (SE)-based experiments SEFT, APT, and SEMUT, and the experiments where the signal intensity is enhanced by heteronuclear polarization transfer such as the INEPT-based experiments INEPT and PENDANT, and the DEPT-based experiments DEPT, POMMIE, and DEPTQ. After a short introduction, this chapter, with the aid of product operator formalism, provides a comprehensive description of these experiments. Building from basic principles, the DEPTQ variant, for including the signals of quaternary carbons, the ACCORDEPT, for equalizing intensities in case of a wide range of heteronuclear coupling constants, and the QDEPT and QDEPT+ sequences, for obtaining quantitative DEPT data are explained in detail.