The 1D HCP (Heteronuclear cross polarization) experiment is an alternative way of polarization transfer from high-abundant nuclei (¹H) to low-sensitive nuclei (¹³C).

Implementation on any AVANCE spectrometer is feasible. Accurate power level and pulse width optimizations in  proton and X-channels are required.

The basic pulse sequence of the 1D HCP experiment ( 78JACS5227 and 91JCP30 ) is very simple:

• A 90º 1H pulse creates transverse ¹H magnetization.
• Heteronuclear polarization transfer is achieved by applying simultaneous pulse trains in both ¹H and ¹³C channels in order to match the Hartmann-Hahn condition for both nuclei.
• Finally, carbon resonances are detected under broadband proton decoupling.

Good heteronuclear polarization transfer can be achieved using isotropic mixing sequences as MLEV-16 ( 91JMR444-91 ), WALTZ-16 ( 91JMR405-91 ), and DIPSI, and the efficiency of these schemes have been analyzed in detail ( 91MP219 and 91JMR413-91 ). A modified version has been proposed for multiplicity editing purposes ( 92JMR143-96 ) by inserting an heteronuclear spin-echo prior to acquisition.

New broadband heteronuclear Hartmann-Hahn sequences have been designed ( 94JMRA115-111 and 97JMR110-126 ).

The 1D HCP experiment can be recorded in routine/automation modes. The most important parameters to optimize are the power level and pulse width in both proton and X-channels in order to match the Hartmann-Hahn condition. In addition, mixing time must be optimized to 1/J(CH).

The 1H HCP experiment affords a ¹H-decoupled ¹³C spectrum with similar sensitivity as achieved using conventional INEPT or DEPT pulse sequences.

The HCP scheme has been used as a useful building block in other experiments:

• 2D HCP experiment
• As a preparation period in a 1D 1H-31P-13C triple resonance experiment ( 95JMRA246-112 ).
• As a preparation period in the GRECCO and 1D INADEQUATE ( 94JMRA113-109 ) experiments.
• As a building block in many multidimensional experiments. For instance: 3D HCCH-TOCSY ( 95JB207 and 97JMR459-124 ) or 4D HN(COCA)NH ( 95JB323 ) experiments