COSY-DQF


The COSY-DQF (Cosy Double Quantum Filter) provides two advantages over the magnitude COSY. Higher resolution is possible and multiplet fine structure can be seen. This may allow proton-proton couplings to be measured. When there are several couplings to a given proton and the multiplet is complex, however, often the cross peak is not interpretable because of cancellation of multiplet components. The E.COSY experiment is usually necessary for coupling measurement.

The DQF version reduces the diagonal dispersive peaks of the COSY experiment but sensitivity is reduced by one half. In addition, uncoupled spins such as water are removed. This experiment is seldom used for small molecules.
Below is a 500 MHz spectrum of sucrose.