What data is this based on?

The data is primarily sourced from Fulmer et al., 'NMR Chemical Shifts of Trace Impurities: Common Laboratory Solvents, Organics, and Gases in Deuterated Solvents Relevant to the Organometallic Chemist', Organometallics 2010.

Can I filter by multiplicity?

Yes. Select a splitting pattern (s, d, t, q, m) to narrow results to Fulmer entries that match both shift and multiplicity.

How do I interpret NMR shifts for unknown samples?

Start by referencing the residual solvent peak (e.g. 7.26 ppm for CDCl₃). Once referenced, match unknown peaks against this table. If a peak matches but the splitting is wrong, it is likely a different compound.

Why are ¹³C shifts less sensitive to solvent than ¹H?

¹³C nuclei are shielded by a larger electron cloud and are less involved in external hydrogen bonding compared to protons, so their chemical shifts are more stable across deuterated solvents.

Can I export my results?

You can copy matched results directly from the match card. Cross-reference with the original Fulmer et al. (2010) publication for formal reporting.

Is spectrum data sent to a server?

No. Matching runs entirely in your browser. Peak lists and chemical shifts never leave your device.

Jaconir NMR Lab

NMR Impurity
Solver

Identify common solvent impurities in proton NMR spectra instantly using chemical shift, multiplicity and solvent information.

InputPredictionMatchConfidenceSpectrum

Demo · CDCl₃ · ¹H

Water

Observed 1.56 ppm · singlet

Confidence 98%Δ 0.000 · Fulmer table

Workspace

Enter sample information — the prediction updates instantly.

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δ —.— ppm

Enter an observed shift to identify the impurity.

Confidence

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1H interactive spectrum

Scroll to zoom · drag to pan · hover peaks

Your inputFulmer matchSolvent / other

Why this matched

Prediction updates as you enter solvent, shift, and multiplicity.

Closest candidates

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Alternative matches

Lower-ranked Fulmer candidates (never shown as confirmed).

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Export / Report

Copy a lab-ready summary of this result for your notebook.

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Data source: Fulmer et al., Organometallics 2010 · Always verify with original spectra · Report a missing peak

Learn & understand

Concepts behind solvent impurity identification in proton NMR

Why solvent impurities occur

Deuterated solvents are never perfectly anhydrous or pure. Trace water, grease, silicone oil, and residual undeuterated solvent appear as sharp, reproducible peaks that can be mistaken for product signals.

Residual solvents

Each deuterated solvent has a characteristic residual proton peak (e.g. CHCl₃ in CDCl₃ at 7.26 ppm). Reference your spectrum to this signal before assigning unknowns.

Reference standards

TMS (0.00 ppm) or the residual solvent peak anchors the chemical shift scale. Impurity tables assume a correctly referenced spectrum — mis-referencing shifts every peak equally.

Why shifts change slightly

Concentration, temperature, pH, and hydrogen bonding move exchangeable and polar peaks by a few hundredths of a ppm. Fulmer values are typical, not absolute.

Multiplicity basics

Singlets (s), doublets (d), triplets (t), and multiplets (m) constrain identity. A shift match with the wrong splitting is usually a different compound.

Common mistakes

Ignoring water vs grease, forgetting solvent-dependent water shifts, and assigning impurities as product CH₂/CH₃ groups are the most frequent errors at the bench.

Continue your NMR workflow

A path from impurity check → prediction → assignment

1
NMR Impurity Solver
You are here
Identify common solvent impurities before assigning compound peaks.
2
NMR Chemical Shift Predictor
Available
Predict unknown proton environments after removing solvent impurities.
3
NMR Splitting Pattern Simulator
Available
Understand why peaks split into doublets, triplets and multiplets.
4
Peak Assignment Assistant
Available
Assign ¹H peaks to atoms with shift, multiplicity, and structure.

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