SpectralBench
Automatic peak detection and functional group assignment
Identifying functional groups from an FTIR spectrum traditionally means cross-referencing peak positions against printed correlation charts or multi-page reference tables. It's time-consuming, error-prone, and especially difficult for beginners learning to interpret spectra.
SpectralBench automates FTIR peak identification: upload your FTIR data, and the peak identifier detects absorption bands, matches them against a curated database of over 80 functional group entries, and returns ranked assignments with confidence scores. You can tune the sensitivity, inspect alternative assignments, and click any peak to highlight it on the chart — all without leaving your browser. Once you have identified your peaks, use the unit converter to express peak positions in wavelength or energy units, or the Beer-Lambert calculator to determine concentrations from measured absorbance values.
Upload an FTIR spectrum in any supported format — JCAMP-DX, SPC, Bruker OPUS, CSV, or TXT. SpectralBench parses the file client-side and renders the spectrum on an interactive chart. The peak detector then applies a prominence-based algorithm to locate absorption bands, filtering out baseline noise and minor shoulders based on your sensitivity settings.
Each detected peak is matched against a curated database of over 80 functional group entries spanning common organic, polymer, and inorganic IR bands. Assignments are ranked by confidence — high, medium, or low — based on how well the observed wavenumber and band shape match the expected ranges for each functional group.
Click any peak in the results table to highlight it on the chart. Expand a row to see alternative assignments and potential interferents — other functional groups whose absorption ranges overlap. Adjust the prominence threshold to detect weaker bands, or reduce the max peaks count to focus on the most significant absorptions. All processing runs in your browser; your spectral data is never uploaded.
Infrared spectroscopy works because molecular bonds absorb infrared light at characteristic frequencies determined by the masses of the atoms and the stiffness of the bonds connecting them. These absorptions appear as peaks (or dips, in transmittance mode) in the spectrum, and each one corresponds to a specific type of bond vibration — stretching, bending, rocking, or wagging.
Functional group correlation is the practice of mapping observed peak positions to known absorption ranges for molecular groups such as O-H, C-H, C=O, and N-H. The infrared spectrum is conventionally divided into characteristic regions where specific bond types absorb, making it possible to identify functional groups even in complex mixtures. SpectralBench's database covers the most commonly encountered functional groups in organic chemistry, polymer science, pharmaceuticals, and environmental analysis.
While correlation charts provide a quick visual reference, automated FTIR functional group assignment goes further by considering exact peak positions, band shapes, and the relative likelihood of each assignment. This is especially helpful for students learning to interpret FTIR spectra and for researchers working with unfamiliar compound classes.
The reference table below summarizes the major spectral regions used in FTIR peak identification. SpectralBench's full database contains over 80 entries with more detailed sub-ranges, band shape descriptors, and interferent information than this summary.
| Region | Wavenumber (cm⁻¹) | Key Functional Groups |
|---|---|---|
| O-H / N-H Stretch | 3200–3600 | Alcohols, amines, carboxylic acids |
| C-H Stretch | 2800–3100 | Alkanes (sp³), alkenes/aromatics (sp²) |
| Carbonyl (C=O) Stretch | 1630–1850 | Ketones, aldehydes, esters, amides, carboxylic acids |
| C=C / C=N Stretch | 1500–1680 | Alkenes, aromatics, imines |
| Fingerprint Region | 600–1500 | Complex overlapping; unique to each compound |
Upload your FTIR data file to SpectralBench in any supported format (JCAMP-DX, SPC, OPUS, or CSV). The peak identifier automatically detects absorption bands and matches each one against a curated database of over 80 functional group entries. Results are ranked by confidence so you can focus on the most likely assignments first.
A strong absorption near 1700 cm⁻¹ typically indicates a carbonyl (C=O) stretch. Depending on the exact position and band shape, it could be a ketone (~1715 cm⁻¹), aldehyde (~1725 cm⁻¹), carboxylic acid (~1710 cm⁻¹), or ester (~1735 cm⁻¹). SpectralBench lists all possible assignments with confidence scores to help narrow the identification.
Automated identification is highly accurate for well-resolved, isolated peaks in standard organic compounds. Overlapping bands, complex mixtures, and unusual matrices may produce multiple candidate assignments — SpectralBench shows all possibilities ranked by confidence so you can apply your chemical knowledge to select the best match.
Peak prominence measures how much a peak stands out from the surrounding baseline and neighboring peaks. A high-prominence peak is a strong, well-defined absorption band, while a low-prominence peak may be a shoulder or noise artifact. Adjusting the prominence threshold lets you control detection sensitivity.
Yes. SpectralBench provides two controls: the prominence threshold, which sets the minimum peak height relative to surrounding data, and the max peaks slider, which limits how many peaks are reported. Lower the prominence threshold to detect weaker bands, or raise it to focus on the strongest absorptions.