What absorbs at 550 cm⁻¹ in an FTIR spectrum?
A band near 550 cm⁻¹ can point to several functional groups. Below are the most likely assignments, ranked by how much published evidence supports each — every one traceable to literature (DOI) and cross-validated against our 130,000+ reference spectra and knowledge graph.
Backed by 8 cited sources
Quick answer
A band near 550 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
| Functional group | Supporting facts | Cited sources | Top confidence |
|---|---|---|---|
| Metal oxygen | 13 | 12 | 1.0 |
| Hydroxyl (O-H) | 7 | 7 | 1.0 |
| Phosphate (PO4) | 6 | 5 | 1.0 |
| Ring structure | 4 | 3 | 1.0 |
| Chlorine | 2 | 2 | 1.0 |
| Metal hydroxyl | 2 | 2 | 1.0 |
| N-O bond | 2 | 2 | 1.0 |
| Amide | 2 | 2 | 1.0 |
| Silicon-oxygen (Si-O) | 1 | 1 | 1.0 |
| Protein | 1 | 1 | 1.0 |
| Phosphorus | 1 | 1 | 1.0 |
| Anhydride | 1 | 1 | 1.0 |
| Borate | 1 | 1 | 1.0 |
| Metal halide | 1 | 1 | 1.0 |
| Siloxane (Si-O-Si) | 1 | 1 | 1.0 |
| Carbonyl (C=O) | 1 | 1 | 1.0 |
| Alkene (C=C) | 1 | 1 | 1.0 |
| Carboxyl (COOH) | 1 | 1 | 1.0 |
| Water (H2O) | 1 | 1 | 1.0 |
| N h | 1 | 1 | 0.6 |
Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.
Possible materials
| Material | Supporting peaks | Overlapping groups | Cited sources |
|---|---|---|---|
| silver nanoparticles | 550, 1636, 1631 | Hydroxyl (O-H) | 2 |
| CeO2 | 550, 1554, 1630 | Hydroxyl (O-H), Metal oxygen | 1 |
| hydrogel | 550, 1632, 1062 | Hydroxyl (O-H) | 1 |
| poly(vinyl alcohol) | 550, 1700, 2993 | Hydroxyl (O-H) | 1 |
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 550 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
-
N-O bond confidence 1.0
“At T ≥ 550 °C no peak can be resolved from the background.”
Deprotonation of Fe-dominant amphiboles: Single-crystal HT-FTIR spectroscopic studies of synthetic potassic-ferro-richterite DOI: 10.2138/am-2017-5859 -
confidence 1.0
“[16] have specified that the peaks at 550 and 440 A are due to the overlapping of Fe-O and Bi-O vibrations.”
Francis 等 - 2016 - Optical nonlinearity in multiferroic bismuth ferri DOI: 10.1016/j.jallcom.2016.07.094 -
Water (H2O) confidence 1.0
“The hydrogel composites showed the large water absorption capacity up to 550 % and could retained water in its matrix for almost 3 weeks.”
Hendrawanh 等 - 2019 - Poly (vinyl alcohol)glutaraldehydePremna oblongi DOI: 10.1088/1757-899X/509/1/012048 -
Carboxyl (COOH) confidence 1.0
“The FTIR spectrum exhibited strong peaks at 550 1500 and cm-1, 3000 which correspond to the presence of carboxylic, alkene groups, and carbonyl groups, respectively [29].”
Biomedical and Textile Applications of Alternanthera sessilis Leaf Extract Mediated Synthesis of Colloidal Silver Nanoparticle DOI: 10.3390/nano12162759 -
Ring structure confidence 1.0
“It showed by the presence of strong band cm-1, around 550 in which the band is assigned to asymmetric stretching vibrations of double 5-ring from MFI structure [12].”
Effect of secondary template polarity to the properties of mesoporous ZSM-5 zeolites DOI: 10.1063/1.4991190 -
confidence 1.0
“Another band observed at cm-1 550 corresponds to the C-Cl bond.”
Synthesis and Catalytic Evaluation of Silver Nanoparticles Synthesized with Aloysia triphylla Leaf Extract DOI: 10.1007/s10876-016-1062-3 -
Amide confidence 1.0
“The differences between pleural mesothelioma and normal pleural tissues identified by comparison of their respective Fourier transform infrared spectra were as follows: (1) a cm-1 higher relative intensity of the protein amide I band at 164”
Qiu 等 - 2020 - Analyses of the Fourier Transform Infrared Spectra DOI: 10.1134/S0030400X2008041X -
Hydroxyl (O-H) confidence 1.0
“Notable bands at 1578cm-1, 1562cm-1 may be assigned to O-C-O stretching or N -coordination through alkaloids 1474cm-1, 1370cm-1 1361cm-1 and ascribed to -O-O-H stretching in the extract Bands at 550cm-1and 500cm-1 vibrations respectively of”
Synthesis of nanostructured CeO2 by chemical and biogenic methods: Optical properties and bioactivity DOI: 10.1016/j.ceramint.2020.02.204
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