How to Set Up Solvent Suppression

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1. Set up your solvent suppression standard file (you only need to do this once).

(a) edc to create a new file.

(b) click the Experiment button, select “…/user” directory on the top right corner dropdown menu, then select WATERSUP1 (more robust) or ZGPR1 (requires more laborious optimization).

(c) check getprosol

 

2. Find the frequency of the solvent (most frequently water) peak. You will need to do this every time you run a solvent suppression experiment. Water suppression only works when the frequency of your pulses is exactly on the water peak.

(a) create a regular proton file and collect a spectrum;

(b) zoom in your solvent peak on the screen;

(c) click this button (set RF by cursor):

watersup-2

(d) left click on solvent peak top, and the following window will pop up. Write down the frequency shown in the pink blank:

watersup-1

(e) click Cancel.

 

3. Run water suppression experiment.

(a) load the water suppression file that you created in step 1;

(b) type o1 (o stands for offset), enter the value you recorded in Step 2.

(c) run your expt like you do any other NMR expt (rga, zg).

(d) use manual phase correction, as apk often has a hard time dealing with the somewhat distorted water peak. Phase it such that your solute peaks are correctly phased, which might mean that the solvent peak has to be left out of phase. This will be addressed in the next step.

4. Optimization

Often the spectrum you obtained above has already achieved good quality water suppression. However, if you wish to improve a bit more (especially if you choose ZGPR1), follow these steps:

(a) display a spectrum range of ca. 1 ppm wide with the solvent peak roughly in the middle. Type dpl1. This defines the spectral range that will be displayed during parameter optimization.

(b) type paropt (which stands for parameter optimization). You will be asked several questions: (1) parameter to optimize. enter o1. (2) beginning value. e.g. if the o1 determined in the last step was 2350Hz, enter 2345. (3) increment. enter 1. (4) number of experiments. enter 11. This will run 11 experiments with o1 ranging from 2345 to 2355.

(c) tighten the paropt step size and find the best solvent suppression. When the suppression is best, the out-of-phase water peak problem will be minimized. You might have to use 0.01 Hz step size to find the best suppression.