16.6 : 非灵敏核的极化转移增强（INEPT）

Insensitive nuclei enhanced by polarization transfer, or INEPT, uses protons or other sensitive, abundant nuclei to strengthen NMR signals originating from low-abundance, low-sensitivity nuclei, like carbon-13 and nitrogen-15.

For example, the proton–carbon-13 pulse sequence involves a combination of 90-degree and 180-degree pulses applied to the high-sensitivity and low-sensitivity nuclei.

Coupling-constant-based delays between pulses allow precise relaxation through space or bond interactions and transfer polarization to low-sensitivity nuclei via spin coupling.

The pulses and delays together invert the net magnetization of protons coupled to carbon-13 in only one of its spin states, ultimately enhancing the carbon-13 signals more than NOE does.

INEPT's effectiveness is seen in the proton-coupled carbon-13 spectrum of pyridine. The three types of pyridine carbon nuclei are all split into doublets of some additional multiplicity. For example, C2 is a doublet of multiplets and is located farthest downfield at about 40 ppm.