The COSY-DQF block is a simple extension of the COSY block in which a multiple quantum filter is inserted to select specific double (or higher) multiple quantum coherences as a function of the used phase cycle or gradient strength ratios.

Easy implementation on AVANCE spectrometers.

 See  2D COSY-DQF and related experiments.

The standard way to implement a COSY-DQF block is:

... p1 ph1 d0 p1 ph2 d13 p1 ph3 ...

in which:

• p1 is the high power 90 degree pulse applied at pl1 from the f1 channel.
• All phases may be specified at the end of pulse program in order to select double, triple or higher-order quantum orders.

. In the case of coherence selection using gradients, the multiple quantum can be specified as:

... p1 ph1 d0 p1 ph2 50u UNBLKGRAD p16:gp1 d16 p1 ph4 ...

or

... p1 ph1 d0 p1 ph2 d20 UNBLKGRAD p2 ph3 d13 p16:gp1 d16 p1 ph4 ...