Deuterium H2 Detection

Deuterium (H2) Detection

Please use the new 400 for H2 detection using the lock channel with the following protocol. This works well with an H2-enriched sample. For best sensitivity if needed, detection through the X-channel is possible.

Note that for the cleanest result, don't use deuterated solvent for detection of D (H2) in your sample. In some cases, however, 10% D-solvent could be used for H2 shimming and locking during the experiment as long as the solvent H2 resonance doesn't interfere with the resonances of your interest.

If 10% deutered solvent is present, try to lock and shim on H2 as usual. Lock signal may be weak. Adjust lock gain and power, or simply click "Lock Find Resonance" button on Start panel for an automatic adjustment.
Enter setexp('H2') to load default H2 detection parameters (using the lock channel). Adjust spectral width and scan numbers (in Acquire panel) and collect and process data as usual.

If your sample doesn't contain deuterated solvent, the experiment has to be run unlocked. You cannot shim on deuterons in this case, which may be Ok if sharpness of the signal isn't of critical interest. Alternatively, you may attempt shimming on a strong H1 signal (in this case it will be the solvent H1 signal. See Manager for steps).

Go to Start->Lock panel and turn lock OFF.
enter alock='n' to turn off autolock adjustment at the start of the experiment.
Enter setexp('H2') to load default H2 detection parameters (using the lock channel). Adjust spectral width and scan numbers (in Acquire panel) and collect and process data as usual.

Referencing H2 Spectrum

If a solvent H2 signal is present in the spectrum, you can use it to reference the spectrum manually just like for H1 spectrm. If not or ambigous, as a valid alternative method, you can also use a referenced H1 spectrum from this sample, collected within the same brief period, to indirectly reference the H2 (or any other) sprectrum.

Using a separate experiment setup (a different exp. number), i.e. under exp2 if the H2 spectrum is under exp1, collect a H1 spectrum and reference it properly.
Go to the H2 spectrum (i.e. use jexp1 if it is under exp1). Then, enter mref(2,1) to reference exp1 (H2 spectrum in this case) using the reference present in exp2. Change exp# according to your situation.

The following applies to H2 detection using the 500.
Deuterium has similar chemical shifts as H1 but its bandwidth in Hz is 7 times smaller (~1600 Hz at 500Mhz) which makes it easier to excite. Accurate integration is achievable. Deuterium detection can be done in one of two ways with wildly different sensitivity, depending on the probe:

Recommended: On a broadband probe (such as SWP on nmr500), the best signal is obtained via pulsing/detection through the broadband X-channel similar to other X-nucleus detection with small cabling changes.
On most probes including an indirect detection probe (such as IDP of nmr400), you can also use the lock channel for H2 detection, albeit with much lower sensitivity depending on probe design. On an IDP probe, pulsing through X-channel is not possible.

In both cases, run the experiment unlocked although a lock diplexer (available on nmr500) offers a choice of locking in between scans when not pulsing if the 2nd method is used.

Sample preparation

In general, two samples of identical sample volume (~700uL) with the same solvent (one with 10% deuteration) are recommended.

Sample 1:

90% protonated with 10% deuterated solvent. Optionally, up to 1% TMS can be added for accurate referencing of H2 spectrum. This sample is mainly used for shimming and testing before running your sample with the compounds.

Sample 2:

100% protonated solvent with your compounds. Use of protonated solvent increases the dynamic range of the receiver/digitizer and reduces interference of solvent signal with H2 signal of interest at natural abundance
Optionally, add up to 1% TMS in this sample for accurate reference.

Procedure for using the X-channel of SWP on nmr500

Step 1: Lock and shim with Sample 1.

Check and set temperature intended for the actual experiment
Insert Sample 1.
Turn spin off for best stability unless slightly better resolution is desired.
Under exp1 (or another experiment), type init1h to load standard shims and 1H parameters. Set solvent, lock and shim. If spin is off, adjust Z1/Z2, then X1/Y1 and re-adjust Z1/Z2.
If TMS is present, collect a 1H spectrum with nt=4 (or multiple of 4) and reference the TMS peak to 0.0ppm. If TMS is not present, type etrefsetref for rough referencing.

Step 2: Set up H2 detection experiment

Type jexp2 (or cexp(2) jexp(2) if exp2 does not exist).
Type setexp('H2') su to retrieve standard H2 detection parameters.

Step 3: Recable and tune X-channel

Insert a tuning stick, labeled 7PF, to the bottom of the probe stick slot.
Turn the top tuning control for the X-channel to display ~46 in the small window on the side of the probe bottom.
Tune/match the probe according to this instruction.
Before reconnect the X-channel probe-to-preamp cable, remove the small square H2 reject filter attached between the preamp (filter has a label NR-76.75-....). Connect the cable to the other filter attached to preamp.
Replace the 1/4-wavelength cable (default cable is for C13 detection) with a cable for H2 detection. The cable should have a frequency coverage including ~76 Mhz.
Disconnect the lock channel cable either from the probe end or the lock filter end.

Step 4: Optional: Test H2 detection with 10% deuterated solvent signal

In exp2, type nt=4 gain=40 go
Type wft, check spectrum width and referencing. Type setref to reference spectrum. If the H1 spectrum is referenced with TMS in exp1, type mref(1,2) to reference the H2 spectrum more accurately.
If no solvent peak is detected, check cable connection, tuning, and parameters.

Step 5: Run actual experiment with sample 2

Insert Sample 2
Turn lock off (lock status displays Off)
Type bs=4 nt=10000 (or another large number) go
Type wft during data collection, aa to stop experiment if signal is good enough or you want to adjust parameters.
To center the spectrum at the solvent signal:
Put single cursor on the solvent peak and type movetof and re-collect data.
To reference the spectrum:
If you have done Step 4, the spectrum should already been referenced. But vnmrJ may change the reference if the spectral width (sw and tof) is changed.
If you need to reference the spectrum again:
If 1H spectrum is referenced by TMS in exp1, type mref(1,2)
OR, for rough referencing, reference the spectrum by the solvent signal.
Alternative method for accurate referencing if TMS is present in Sample 2:
In exp1, collect a H1 spectrum with gain set low (gain=10 or gain='n' to use autogain) to prevent receiver/ADC overflow. Reference TMS peak to 0.0ppm.
In exp2, collect and process H2 spectrum. Type mref(1,2) to reference the H2 spectrum.

Step 6: Finishing up: recable and tune X-channel for C13

After your experiment is done, type tn='C13' su under any experiment
Remove H2 tuning stick from bottom of probe
Turn the top portion of the X-channel tuning control to display ~30 in the small window on the side the probe.
Tune X-channel back to C13
Re-attach the square no-pass H2 filter back to the end of the other filter attached to the broadband preamp.
Re-connect the lock channel cable between the probe and lock bandpass filter.
Replace the 1/4-wavelength cable for H2 with the one for C13.

H. Zhou updated Dec 2010