What absorbs at 1391 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 1391 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.

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 1391 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

• Borate

  Reported band

  1391 cm-1

  Assignment

  Borate

  Material / context

  boric acid; alcohol; reticulated three-dimensional network ablative composites

  Reticulated three-dimensional network ablative composites for heat shields in thermal protection systems DOI: 10.1039/c4ra05811a
• Phosphate (PO4)

  Reported band

  1391 cm-1

  Assignment

  Phosphate (PO4)

  Material / context

  Acidovorax citrulli; Acidovorax oryzae

  Differentiation in MALDI-TOF MS and FTIR spectra between two closely related species Acidovorax oryzae and Acidovorax citrulli DOI: 10.1186/1471-2180-12-182
• Hydroxyl (O-H)

  Reported band

  1391 cm-1

  Assignment

  Hydroxyl (O-H)

  Material / context

  Izu-Bonin arc; melt inclusions; silicic volcanic glasses

  Spectroscopic FTIR imaging of water species in silicic volcanic glasses and melt inclusions: An example from the Izu-Bonin arc DOI: 10.1016/j.jvolgeores.2006.03.024
• Alkyl C-H

  Reported band

  1391 cm-1

  Assignment

  Alkyl C-H

  Material / context

  bio-char

  Co-pyrolysis of rice straw and water hyacinth: Characterization of products, yields and biomass interaction effect DOI: 10.1016/j.biombioe.2019.105281
• C-O single bond

  Reported band

  1391 cm-1

  Assignment

  C-O single bond

  Material / context

  XN molecule; xanthohumol cocrystals

  Formation of Prenylated Chalcone Xanthohumol Cocrystals: Single Crystal X-ray Diffraction, Vibrational Spectroscopic Study Coupled with Multivariate Analysis DOI: 10.3390/molecules24234245
• Hydroxyl (O-H)

  Reported band

  1391 cm-1

  Assignment

  Hydroxyl (O-H)

  Material / context

  polymer coated alumina; Polymer Coated Alumina Surfaces; modified alumina

  Characterization of Modified and Polymer Coated Alumina Surfaces by Infrared Spectroscopy DOI: 10.1155/2013/706960
• Carbonate

  Reported band

  1391 cm-1

  Assignment

  Carbonate

  Material / context

  Topolița-Neamț County; Chalcolithic Pottery from Topolița-Neamț County; Chalcolithic Pottery

  Archaeometric Investigations of the Chalcolithic Pottery from Topolița—Neamț County, Romania DOI: 10.3390/coatings13030488
• Alkyl C-H

  Reported band

  1391 cm-1

  Assignment

  Alkyl C-H

  Material / context

  Lithium-ion Batteries; SEI layer; composite electrodes of lithium-ion batteries

  In-operando FTIR Spectroscopy for Composite Electrodes of Lithium-ion Batteries DOI: 10.5796/electrochemistry.83.874