Many experiments on samples dissolved in H₂O solution require some method to minimize the strong resonance belonging to the solvent. This suppression can be performed of several ways, depending of the selected method and depending in which part of the pulse sequence is incorporated. Solvent suppression can be included during the relaxation period just prior to the conventional pulse sequence.

A lot of methods are available (see solvent suppression schemes) although the classical solvent presaturation is one of the most widely used.

However, presaturation can also reduce the signal intensities of exchangeable protons. For this reason, other schemes, as the WET and CHESS schemes, have been proposed.

In HPLC-NMR applications it is mandatory to suppress multiple-solvent resonances. The incorporation of specific multiple-solvent suppression schemes into pulse sequences is made in analogy with classical methods.

Easy implementation on AVANCE spectrometers.

For further details about implementation of solvent suppression  schemes in AVANCE spectrometers see:

• Tutorial: Solvent Suppression schemes.

The standard way to implement solvent presaturation during the relaxation delay  in a pulse program is:

... d12 pl9:f1 d1 cw:f1 ph29 d12 do:f1 d12 pl1:f1 ... ph29 = 0

in which:

• d1 is the presaturation delay (usually 1.5-2 seconds)
• pl9 is the power level for presaturation (around 55-60dB). f1 means that the f1 channel is used for this purpose. Usually the presaturation pulse is applied along an specific axis defined by the phase program ph29.
• A short delay d12 (20 usec) is needed to set the power levels and to stop the irradiation with the do:f1 command. In addition, another power level change to pl1 is usually required at the end of this block to apply the following pulses in the common way.

Example of basic pulse sequences using presaturation: Other solvent suppression methods: