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This article explains how to suppress solvent peaks in 1H and 13C NMR using robust pulse programs, parameter tuning, and sample preparation so spectra remain quantitative and interpretable.
1. Start with the highest leverage controls
Choose an appropriate deuterated solvent. Match solvent polarity to solute. Verify solubility at target concentration. Filter particulates with 0.2 µm PTFE. Add 0.01–0.03% TMS only when needed. Use fresh, dry solvents for exchangeable protons. Degas if paramagnetic oxygen affects T2. Use 5 mm tubes with correct filling height. Shim to line widths ≤ 0.8 Hz on 1H. Lock and reference correctly.
Caution: Avoid non-deuterated co-solvents unless the pulse program and power settings were designed to suppress them.
2. Pick a solvent suppression method aligned to chemistry and goals
| Method | Best use case | Strengths | Pitfalls | Key parameters |
|---|---|---|---|---|
| Simple presaturation (1D) | Quantitative 1H where solvent far from analyte peaks. | Fast. Robust. Low setup cost. | Can distort integrals near the sat band. NOE artifacts. | O1P offset. PLdB or B1 field. Sat time d1sat. Shaped pulse type. |
| Excitation sculpting (PFG) | Crowded regions near solvent. Minimal excitation of analyte. | Narrow stopband. Clean baselines. | Gradient calibration required. More sensitive to shim. | Shaped 180° pair. Gradient strengths. Sweep width centered at solvent. |
| WATERGATE | Water suppression in aqueous or H2O/D2O mixes. | High dynamic range. Minimal NOE transfer. | Requires accurate pulse calibration. Sensitive to J and B1 inhomogeneity. | Flip angles. Gradient ratios. Delay tuning for chemical shift evolution. |
| WET (multiple band) | Multiple solvents or impurities to null. | Multi-frequency notches. Flexible shapes. | Longer sequence. More parameter coupling. | Number of bands. Bandwidth per shape. Inter-pulse delays. |
| DPFGSE (double PFG spin echo) | 1D spectra near strong solvent with diffusion filtering. | Suppresses convection and artifacts. | Signal loss for small molecules with high diffusion. | δ, Δ, gradient strength. 180° pulse calibration. |
| Perfect-echo solvent suppression | Samples with strong homonuclear J coupling near solvent. | J-refocusing improves resolution. | Sequence-specific delays must match J. | τ = 1/(2J). Phase cycle. Gradient scaling. |
| T2 filter (CPMG) | Remove broad residuals or macromolecular background. | Attenuates short-T2 signals. | Also reduces broad analyte peaks. | Echo count. τ-echo. Total filter time. |
3. Parameter selection that prevents analyte loss
Center the selective irradiation exactly at the residual solvent frequency. Use a narrowband shape when analyte peaks are nearby. Use a broader shape if the solvent drifts with temperature. Keep the saturation field B1 as low as possible while achieving target suppression ratio. Validate with a control scan without suppression to confirm integral fidelity.
Caution: Do not place the sat band within 30–50 Hz of any analyte peak intended for integration.
4. Practical presets in common environments
These examples are starting points. Fine-tune on your system with actual line widths, gradients, and temperature.
# Bruker TopSpin: 1D presaturation getprosol rpar "zgpr" # gradient-enabled presat o1p = 4.700 # water at 25 °C, adjust for solvent plw = 3.0 # start low; calibrate B1 d1 = 3.0 # relaxation delay; increase for quantitative work d1s = 2.0 # presaturation duration within d1 ns = 16 zg
Bruker TopSpin: Excitation sculpting near residual CHCl3 at 7.26 ppm
rpar "zgesgp"
o1p = 7.260
p1 calibrated for 90°
gpz1 = 30 # gradient percent; calibrate on your probe
gpz2 = 17
ns = 32
zg
Agilent/Varian VNMRJ: WATERGATE for H2O/D2O
go(watergate)
satfrq = 4.700
satpwr = -10 # dB; adjust to just reach target suppression
satdly = 2.0
nt = 16
ga
5. Compute safe selective bandwidth before you suppress
The nutation frequency ν1 sets the approximate selective saturation bandwidth in Hz. Calibrate on your probe.
# Selective saturation bandwidth estimate # ν1 ≈ γ * B1 / (2π) [Hz] # For a 1H 90° pulse of length p90 (s), ν1 ≈ 1 / (4 * p90). # Example: p90 = 10 µs → ν1 ≈ 25 kHz. Use shaped pulses to narrow this by 10–100×. Caution: Large B1 fields increase sample heating and can saturate nearby analyte peaks. Favor shaped low-power pulses for selectivity.
6. Residual solvent chemical shifts to set O1P quickly
| Solvent | Residual 1H (ppm) | 13C (ppm) | Notes |
|---|---|---|---|
| D2O | 4.79 at 25 °C | Not applicable | Shift depends on temperature and pH. |
| CDCl3 | 7.26 | 77.16 triplet | Add drying agent if water shoulder appears. |
| DMSO-d6 | 2.50 | 39.52 | Water appears near 3.33 ppm. |
| Acetone-d6 | 2.05 | 29.84 | Water near 2.84 ppm. |
| MeOD-d4 | 3.31 | 49.00 | Exchange broadening common. |
| Acetonitrile-d3 | 1.94 | 118.69, 1.32 | Watch for temperature drift. |
| Toluene-d8 | 2.09 and 7.09 | 137–125 region | Viscosity increases T1. |
Caution: Verify your spectrometer reference. Report chemical shifts versus TMS or internal standard for reproducibility.
7. Quantitative work without bias
Use long relaxation delays. Set d1 ≥ 5× the longest T1 among quantified peaks. Disable presaturation during acquisition windows of quantitative experiments such as inverse-gated 1D 13C. Where suppression is mandatory, report conditions and validate linearity with a standard mixture.
8. Troubleshooting checklist
- Suppression not deep enough. Increase presat duration. Re-center O1P. Use a narrower shaped pulse. Improve shim on Z2 and Z3.
- Analyte peaks attenuated. Reduce B1. Shorten presat. Switch to excitation sculpting or WATERGATE.
- Baselines distorted. Recalibrate gradients. Reduce gradient strengths by 10–20%. Lengthen recovery delays after gradients.
- Solvent drift with temperature. Track peak position and enable real-time O1P updates or widen the stopband slightly.
- Exchangeable protons lost. Use WET or sculpting rather than continuous presat. Lower temperature if compatible.
9. Example reporting language
"1D 1H NMR (400 MHz, CDCl3). Solvent suppression by excitation sculpting centered at 7.26 ppm. Shaped pulses calibrated to 90° at 10 µs. Gradients 30%/17%. Residual CHCl3 < −50 dB relative to TMS. Relaxation delay 5 s. 16 scans." FAQ
How do I keep integrals accurate with suppression on?
Place the stopband far from peaks used for integration. Use minimal B1 power. Validate with a non-suppressed control. Prefer excitation sculpting over continuous presat when peaks are close.
What if my sample needs a non-deuterated co-solvent?
Use multi-band WET or excitation sculpting with multiple notch frequencies. Consider reducing the co-solvent fraction. Re-reference with an internal standard.
Why does water suppression vary with temperature?
The water chemical shift and exchange rate change with temperature and pH. Re-center O1P after each temperature change. Consider broader but low-power shapes to maintain selectivity.
Can I combine diffusion filters with solvent suppression?
Yes. Use DPFGSE or DOSY-type modules followed by a selective notch. Expect some loss of small-molecule signal. Tune gradients to avoid over-attenuation.
How much suppression is enough?
Target at least −30 dB for routine work and −50 dB for aqueous samples with strong water signals. Confirm on the same receiver gain and processing.