Running Deuterium (H2) NMR at SCS NMR facility

Transcription

1 Running Deuterium (H2) NMR at SCS NMR facility (A) on ui600 using AutoX probe or triax probe (B) on VXR500 using lock channel (C) on ui500nb using lock channel L Zhu 5/8/2012 There are 2 ways to collect a H2 NMR spectrum, one is using the lock channel (lower sensitivity); the other is treating it as a normal X nucleus and collecting the H2 NMR spectrum on a broadband channel. Using lock channel is quick easy and is typically recommended for most of Deuterium NMR experiment. However if your sample concentration is low, performing the experiment on ui600 using AutoX probe is recommended. Important: (1) Sample should be prepared in a non deuterated solvent to avoid overflow of solvent signals. The H2 isotopic peak of the non deuterated solvent can often be observed and used as a reference signal. (2) The natural abundance H2 signals of the solvent are observable. (3) The H2 chemical shifts are equivalent to the H1 chemical shifts. (4) H2 NMR data are collected without locking (no lock signal), so you should shim the sample in FID mode; or preparing a sample with a 90% protonated with 10% deuterated solvent (no compound needed), shim on this sample, then insert the real sample using the shimmed values just obtained; or the best method: is to do H1 gradient shimming on the sample (see instruction below). (A) On ui600 using AutoX Probe (A1) using AutoX probe X channel: (1) Setup H2 experiment: click on Main Menu > Setup >Nuc,Solv > H2 > solvent, then type su (2) autotune H2 (a separate user handout) (3) The H2 reject filter that is normally used on the Broadband of Preamp (at port J5311) should be taken off, as well as the lock cable (lk) (one end to the probe, the other end connects to H2 filter) which should be disconnected at the end of the H2 filter. The H2 filter is located on the floor between the Preamp stand and the Mag leg (see Fig 1 and Fig 2) (4) Set the Z0 value to the number given on page 3 of the document for the corresponding deuterated solvent. If the solvent you are using is not given, you can measure it using the deuterated solvent before running the H2 experiment (5) Gradient shim on H1 signals, procedure given below (page 3). (6) Collect H2 spectrum. The sensitivity of H2 is about 1/6 of H1 signal for an isotope enriched sample. If you are looking at the natural abundance H2 signal (0.0155%), do expect a weak signal, if any peak at all. Page 1 of 10

2 After you re done, connect the H2 reject filter and lock cable to the original configuration (Fig. 2). Fig 1. When performing H2 experiment Page 2 of 10

3 Fig. 2. Original configuration Page 3 of 10

4 Proton (H1) gradient shimming on ui600 (1) Using the menu buttons click on: Main Menu > Setup > H1 experiment and choose the solvent (2) Type: gmapsys (gradient menu buttons appeared) (3) Click on Shim Maps > Current Mapname. If the current mapname is autox H2O , you can click on Return. If the current mapname is not the above, click on shimmap files > Cd to Userdir > highlight the file name map, click on Load Shimmap and Parameter. Then click on Return. (4) Make sure tn= H1, nt=1, and gzsize=4 click on Autoshim on Z (5) The shimming will take a couple of minutes, while shimming the spin goes to zero (6) Once the shimming is finished, Click on Quit to go back to the normal experiment (7) Open the acqi windon, set SPIN ON and LOCK OFF (7) Proceed to collect the spectrum: Setup H2 experiment: click on Main Menu > Setup >Nuc,Solv > H2 > solvent. Note: the names of the shimmap on vxr500 and ui500nb are QUADG H2O and hcn 45mm, respectively. Z0 values of AutoX probe (8May 2012) solvent Z0 D 2 O 252 CD 2 Cl 2 (DCM) 488 CDCl 3 (Chloroform) 3929 C 6 D 6 (benzene) 4547 DMSO d Acetone d Toluene d 8 (lock on CD 3 ) 5273 (A2) using AutoX probe lock channel: This method is fast and easy to perform (no H2 tuning needed) but the sensitivity is lower than the method above. (1) Disconnect the J5 PT cable (one end at the Protune Preamp stand (the far left box at the Preamp stand), the other end connects to H2 reject filter and low pass filter on port J5311 of the Preamp) at the connection between the two filters (2) Disconnect the lock cable at the top of the H2 filter (a foot long cylindrical) next to the Mag leg. (3) Find the spare cable (~ 1 foot long) on the floor next to the Mag. Leg (4) Connect this new cable to top of the H2 filter, and connect the other end to the probe port (J5311) of the broadband of the Preamp after the low pass filter (Fig. 3) (5) Set Z0 as described above, and turn OFF lock Page 4 of 10

5 (6) Perform H1 Gradient shim (7) Set up the H2 experiment: click on Main Menu > Setup >Nuc,Solv > H2 > solvent. (8) Type tpwr=45 pw=100 dm= nnn, nt=16 or more, ga to collect H2 spectrum (please note: you are using lock channel and lock coil to perform H2 experiment. Lock coil cannot handle high power, therefore, use lower tpwr power such as 45) (9) When you re done, put the J5 PT cable, H2 reject filter and lock cable to their original positions (Fig 2). Fig 3: Configuration when using lock channel for H2 experiment. (A3) Using Triax probe lock channel: This method is fast and easy to perform (no H2 tuning needed) but the sensitivity is lower than observing H2 using X channel of AutoX probe. Page 5 of 10

6 (1) Disconnect the lock cable at the top of the H2 filter, and use a spare cable: one end to the H2 filter, the other end connects to the open port on the broadband of Premap (J5311) after the low pass filter. Don t forget to remove the H2 reject filter that is usually connects to the lowpass filter (Fig. triax 1). (2) Set Z0 as described above, and turn OFF lock (3) Perform H1 Gradient shim (4) Set up the H2 experiment: click on Main Menu > Setup >Nuc,Solv > H2 > solvent. (5) Type tn= H2, or lk, tpwr=45 pw=100 dm= nnn, nt=16 or more, ga to collect H2 spectrum (please note: you are using lock channel and lock coil to perform H2 experiment. Lock coil cannot handle high power, therefore, use lower tpwr power such as 45) (6) When you are done, put everything back to its original position (Fig triax 2). Fig triax 1: configuration during deuterium NMR experiment Page 6 of 10

7 Lock cable H2 reject filter open end spare cable H2 filter Lock cable Fig triax 2: Original configuraiton Page 7 of 10

8 (B) Using the lock channel on VXR500 spectrometer: A deuterium module was installed on this spectrometer, therefore collecting deuterium H2 NMR on this spectrometer is the quickest and easiest among 3 spectrometers. Note: theoretically you can perform H2 NMR on any spectrometer using lock channel (lk). However due to practical reason especially the ease of shimming, the spectrometers equipped with a probe with gradient capability are highly recommended. That is: vxr500, ui500nb and ui600 spectrometers. (1) logon to vxr500 spectrometer as usual (2) When the Nalorac QUADG probe is installed on the spectrometer (default probe), you can perform H1 gradient shimming. For probes other than the QUADG, shimming on FID or on a 90% protonated/10% deuterated solvent. (3) Turn the LOCK OFF in acqi window (4) Perform H1 gradient shim (see document on page 3, please pay attention to the name of the shimmap: QUADG H2O ) (5) After setting up a normal proton spectrum, changing tn= lk (6) Lock channel only handles low power, therefore the tpwr should be reduced, type tpwr=45, pw=100 for using lk coil. (7) You may need more scans (nt), and also use smaller sw value (8) Collect the H2 spectrum Please note, the chemical shifts of deuterium is random (due to the lack of locking during data collection), please reference your spectrum using the natural abundance H2 signals of the solvent or spike (add a few microliter) your sample with deuterated solvent. (C) Using the lock channel on ui500nb spectrometer (1) logon to ui500nb as usual (2) The default probe on ui500nb is the hcn probe, you can perform H1 gradient shimming on your sample as described on page 3 in this document (3) After shimming is done, turn the LOCK OFF in acqi window (4) Re cable the lock cable as follows (Fig 4 and Fig 5): (a) Locate the lock cable labeled lock or lk (red tape), one end of the lock cable connects to the large cylindrical H2 filter (~ 1 foot long, lock filter) normally located between the Mag leg and the Preamp stand, the other end of the lock cable goes to the probe lk port. (b) The top end of the cylindrical H2 filter connects to a cable on the side of the Mag Leg (the vertical gray magnet/interface rectangular box) (Fig 4), disconnect this cable from the top of the H2 filter (c) Find another spare cable on the floor next the Mag leg Page 8 of 10

9 (d) Connect this new cable to the top of the H2 filter (e) Connect the other end of this new cable to the Probe port (J5311) of the broadband of the Preamp stand (the one has tune interface indicator in the middle of the unit) after low pass filter (Fig 4). Please note, you need to disconnect the cable that is already there (normally labeled as X cable), and also take off the H2 reject filter which connects to the low pass filter (h) Above setup allows the observation of H2 or lk signals through lock channel (lock coil). (5) After setting up a normal proton spectrum, changing tn= lk or tn= H2 (either one works). Again we are using lock coil, lower power should be used. Type: tpwr=45, pw=100, nt=16 or more. Collect H2 spectrum. When you are done, put everything back to their original configuration (Fig 4). top of the H2 filter H2 filter Lock (lk) cable H2 reject filter spare cable X-cable Fig 4: original configuraiton Page 9 of 10

10 Fig 5: configuration for deuterium NMR Page 10 of 10