2D Phase Correction

Phase Correction is used to make the resonances in the Fourier Transformed data purely positive (TOCSY, gHSQCSE), positive and negative (NOESY, ROESY, gHSQC) or positive/negative (DQF-COSY).

The Phase Correction menu is located under the Processing tab then Phase Correction.

There are 4 options under the Phase Correction menu- Automatic (with Options below it) for both dimensions, Manual Correction, Magnitude and Power. In most cases, Automatic Phase Correction will work well, but if it does not then you will need to use the Manual Phase Correction. The Magnitude and Power options are used to make all parts of the spectrum positive and lead to long tails on resonances.

1) In most 2D spectra, the Automatic Phase Correction will work well in both dimensions. To confirm, increase the vertical scale to see the base of the cross peaks or diagonal peaks. If you observe noise on either side of the peak, note the color of the noise. If it is blue on one side and red on the other, that is a phase problem. If the noise is the same color, that is a baseline problem, see baseline correction:
2D Baseline Correction

2) If Automatic Phase Correction is not optimal, then choose Manual Phase Correction. The most likely reasons for imperfect phasing are low signal-to-noise, poor shimming, very broad resonances, or some issue with data acquisition.

3) The 2 phase parameters are PH0 and PH1, the zero-order and first-order phase corrects, so frequency independent and frequency dependent (rp and lp in VNMR). The PH0 should change the phase equivalently across the spectrum, the PH1 will change the phase differently across the spectrum as it has a frequency component.

4) Set the pivot parameter to the biggest peak in the spectrum (you can click on Biggest to do this). The pivot point will not change when adjusting the PH1 parameter. Next adjust the PH0 parameter with the left mouse button until the biggest peak is phased well. Finally, adjust the PH1 with the right mouse button until the rest of the spectrum is phased.