1D H1 and C13 Detection

H1 detection is the most basic experiment a user should be familiar with before attempting other experiments. On all instruments (except Bruker NMR800) the in-house initialization script init1h sets default H1 detection parameters. The following instructions are detailed during training, and are listed only briefly here.

Sample volume:

• Keep sample volume as close as possible to 700uL. Lower volume often leads to bad signal-to-noise and lineshape. With 700uL sample volume, quick Z1/Z2 adjustment is mostly adequate if manual shimming is used.

H1 detection steps

• Enter e (or click Eject button) to eject current sample. Enter i (or click Insert button) to load your sample.
• Enter init1h in the command line. The script (or macro) does the following:
• Load standard H1 parameters
• reset shims to optimized default values
• change solvent to CDCL3
• Set lock power, gain, and phase for CDCL3. Note this lock phase setting is good for all solvents.
• Change solvent from the pulldown menu under Start→Standard
• Make sure sample spins at 20 Hz
• If not, click Start→Spin or Start→Spin/Temp to turn on spinning
• Adjust Z0 so that the H2 excitation (or lock) is on resonance
• If autolocking is available (NMR500 and NMR600), click Start→Standard→Find Z0
• If autolocking is not possible (NMR400), click Lock→Lock Scan, turn lock off and manually adjust Z0 so that a step-function is seen. Once lock is on-resonance, turn lock ON.
• Shim: optimize field homogeneity
• If autoshimming is available (NMR500 and NMR600), click Start→Standard→Gradient shim. The solvent display switches to D2O during shimming and will switch back to selected solvent after shimming.
• If autoshimming is not possible (NMR400), click Start→Shim and manually shim Z1 and Z2. Iteratively adjust Z1 and Z2 values so that the lock level (from 0 to 100%) is optimized to maximal level at set power and gain.
• Readjust gain or power to have lock level ideally at ~70-80% before data collection.
• Start experiment
• Adjust parameters:
• Set number of scans (or transients), i.e. nt=1000
• To change spectral width, go to Acquire→Default
• Enter go or ga (or click Acquire→Acquire or Acquire→Acquire & Transform)
• Process data
• Enter wft aph dc vsadj (or click Process→Autoprocess)
• Default line broadening factor lb=0.2 in Hz. Typical value to use for small molecule is 0.1 to 1. Use larger value for spectrum with broad peaks. The goal is to smooth the noise but not to add much to natural linewidth. If lb is changed, repeat the processing command above.
• To reference specrum:
• Enter setref
• Or: reference to the cursor line with command rl or under Process→Default
• Increase the vertical scale to show baseline and phase defects.
• Manually adjust phase if necessary to give all absorptive signals (via Phase Mode button on the right side)
• Baseline correction: Define baseline regions through the same integral reset points picking. Cover all peaks with green lines (regions in between green lines are defined as baseline regions). Enter bc to apply baseline correction.
• Default bs=4. New data are available every 4 scans. Stop experiment by entering aa (or click Stop) when signal-to-noise is acceptable.
• Process final data. Re-apply bc as long as baseline definition is still available.
• Pick integral reset points (manually pick zero baseline points for an integral)
• Print
• Save data
• Enter svf at the command line, or click File→Save

C13 detection steps (preferably on NMR500 and NMR600 where the X-channel is tuned to C13 at all time)

This experiment is a basic C13 detection experiment with H1→C13 NOE.

• Follow steps for H1 detection to lock and shim
• Enter setexp('C13')
• Paramater adjustment:
• nt (set to large number by default)
• Adjust spectral width in Acquire→Default
• Leave other parameters at default values
• Submit experiment with go
• Process and save data as detailed above.
• Typical lb=0.5 or 1 for C13

H. Zhou updated Aug 2011