Manual Phase Correction
A taste for symmetry is widely distributed among human beings, therefore no particular skill is required to become a master in this technique. Just follow these steps:
- Choose the command: 'Process/Phase Correction' to bring the phase window into the foreground.
- If the spectrum has 2 dimensions, select either the 'vertical' or the 'horizontal' button. [The former is dimmed if you forgot to activate the “ HyperComplex” button]
- Visually examine the spectrum and find the peak nearer to the 'in phase' condition.
- Place a mark on it. A vertical mark if you are phasing the horizontal dimension, an horizontal mark if you are phasing the vertical dimension.
- Change the first order coefficient. You can use the numerical field, the small arrows or the slider on the right.
- Continue until the peaks farther away from the mark are in phase.
- If you feel to have little control over the coefficient, move the selector at the bottom from 'Coarse' to 'Fine'.
- If the thumb reaches the end of the slider, move the 'Coarse/Fine' selector into any position other than the current position.
- Locate the peak which has become by now the most symmetric one and move the red mark on it. You can drag the mark with the mouse.
- If the spectrum isn't in phase yet, go back to step 5.
Some rules can be precious for the beginner, especially in difficult cases:
- The numerical values of the first-order correction coefficient rarely exceed ±200°. If you arrive at such a value and feel you are still far from the solution, reset all coefficients to zero.
- While you correct the phase, the window should be as large as possible and the spectrum is to be magnified ten times more than normal
- You should exclusively look at the tails of the peaks. Your aim will be to make the tails as short as possible (that's what phase correction is all about).
- Sometimes you can put in phase all the peaks but one outlier, typically a solvent peak. Don't care about outliers. Don't care at all.
- In 13C spectroscopy, apply an exponential broadening before attempting phase correction; this is a good rule when using automatic correction too. Do not work on the whole spectrum. Cut away regions of pure baseline, making repeated use of both the zoom tool and the cutter tool.
- Although an expert will prefer to phase a 2D matrix as a whole, the beginner should start working on 1D extracts exclusively.