What absorbs at 3230 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 3230 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.

Possible functional-group assignments

Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.

Possible materials

Materials are shown only when the same literature pool supports this band and at least one additional characteristic peak.

Spectrum logic

This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 3230 cm⁻¹ is usually not enough for material identification by itself.

Real-world usage

This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.

Common mistakes

• Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
• Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
• Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.

Verification advice

When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.

Literature behind these assignments

• Water (H2O) confidence 1.0

  “Explicit: 'a shoulder at about 3230 cm-1'.”

  Ashraf 等 - 2021 - Identification and properties of ion-pairs in the DOI: 10.1016/j.molliq.2020.114891
• Hydroxyl (O-H) confidence 1.0

  “The absorption cm-1 -OH peak at 3230 representing the stretching vibration caused by absorbed water on the surface of the spheres shifted cm-1 toward 3480 and reduced the intensity with the increase”

  Kim 和 Kang - 2012 - Fabrication of a Crack-Free Large Area Photonic Cr DOI: 10.1021/cg3005147
• Hydroxyl (O-H) confidence 1.0

  “When MSA bonds to the surface of of the The obvious but relatively weak absorption cm-1 gold nanoparticles and forms carboxylate during nanoparticle peak at 3230 is therefore attributed to the OH vibrational preparation, a water molecule st”

  Wang 等 - 2004 - Inclusion-water-cluster in a three-dimensional sup DOI: 10.1021/ja031822
• Alkyl C-H confidence 1.0

  “2911 CH2 Asymmetric stretching Polyethylene 2846 CH2 Symmetric stretching 3230”

  Modification of surface characteristic and tribo-electric properties of polymers by DBD plasma in atmospheric air DOI: 10.1051/epjap/2017170149
• Hydroxyl (O-H) confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Galvez 等 - 2008 - Trapping and adsorption of CO2 in amorphous ice A DOI: 10.1016/j.icarus.2008.05.016
• Hydroxyl (O-H) confidence 1.0

  “at 957 cm-1 and 1033 cm-1, the internal hydroxyl band at 3230~3550 cm-1.”

  Properties and Mechanism of Hydroxyapatite Coating Prepared by Electrodeposition on a Braid for Biodegradable Bone Scaffolds DOI: 10.3390/nano9050679
• Hydroxyl (O-H) confidence 1.0

  “The low-intensity broad peak at the 3230 cm-1 band corresponds to the elongation of -OH groups found in D-glucose units [15,35].”

  Development and Characterization of Yellow Passion Fruit Peel Flour (Passiflora edulis f. flavicarpa) DOI: 10.3390/metabo13060684
• confidence 1.0

  “Furthermore, in case of the orthopyroxenes and clin- ~3230cm-1 (<3600cm-1 is linked to hydrogen incorporation into octahedral (Mg) opyroxenes bands at lower wavenumbers and<3630 cm-1, vacancies [Mg] (e.g.”

  Extremely low structural hydroxyl contents in upper mantle xenoliths from the Nógrád-Gömör Volcanic Field (northern Pannonian Basin)_ Geodynamic implications and the role of post-eruptive re-equilibration DOI: 10.1016/j.chemgeo.2018.12.017