Fourier Transform Infrared Spectroscopy
Identification of functional groups and molecular characterization by infrared absorption.
O que é FTIR
How FTIR Identifies Functional Groups from Infrared Absorption Fingerprints
FTIR (Fourier Transform Infrared Spectroscopy) is a technique that passes infrared radiation through or off a sample and measures which wavelengths are absorbed as molecular bonds vibrate at their characteristic frequencies, producing a spectrum, typically plotted in wavenumbers from about 4000 to 400 per centimeter, that acts as a molecular fingerprint. Peak positions and shapes identify the functional groups present, such as carbonyls, hydroxyls or amines, and the overall spectral pattern can confirm compound identity, detect contamination or track chemical changes such as oxidation or curing. FTIR requires minimal sample preparation, particularly with an ATR accessory, and works on solids, liquids and films alike.
Variantes de FTIR
Configurações disponíveis
FTIR-ATR (Attenuated Total Reflectance)
Fourier-transform infrared spectroscopy with an attenuated total reflectance accessory for fast surface and bulk identification with minimal sample preparation.
FTIR Transmission
Fourier-transform infrared spectroscopy in transmission mode, passing the beam through a thin or diluted sample for quantitative, path-length-defined absorbance measurements.
Comparação de configurações
Resolução, o que revela e preparo por configuração
| Configuração | Resolução | O que revela | Uso típico | Preparo de amostra |
|---|---|---|---|---|
| FTIR | Typically 4 cm⁻¹ standard spectral resolution, set by the interferometer and detector rather than by the accessory used. | A general functional-group fingerprint of the sample — the vibrational bands used to confirm identity, detect impurities, and assess polymorphic form. | Applies across every configuration below; the specific accessory (ATR or transmission) is chosen based on the sample's physical form and the analytical goal. | Varies by the configuration selected — see the ATR and transmission rows below. |
| FTIR-ATR | Comparable nominal resolution to transmission, but the beam only penetrates a few micrometers into the sample surface. | Surface-region chemistry — ideal for coatings, raw materials and fast identity checks where only the outer layer matters. | Solids, pastes, gels and liquids analyzed directly against the ATR crystal — fast QC screening and samples that can't be pressed into a pellet or cast as a film. | Minimal to none — the sample is pressed against the ATR crystal as-is. |
| FTIR-Transmission | Comparable nominal resolution to ATR, generally with higher spectral fidelity since the full sample thickness is probed rather than only the surface. | Bulk-phase molecular composition through the full sample thickness — better suited to precise band-shape work and low-concentration analysis. | Thin films or KBr pellets of solids, or free-standing liquid films — used when bulk composition (not just the surface) matters or when the highest spectral fidelity is required. | Moderate to high — solids require grinding and pressing into a KBr pellet, or casting a thin film. |
What sets us apart
We don't hand over a spectrum. We hand over the interpretation.
Any lab can return peaks and numbers. Our report reads the data. Three differences define what we deliver — illustrated below with a real, anonymized case.
Multiple techniques, one integrated report
We don't hand back five loose reports. We cross-reference every technique's results into a single reading — each signal checked against the others — to reach an answer, not a pile of data.
- Contamination investigation — identifying and tracing the source of a foreign species.
- Performance degradation — explaining why a batch behaves outside expectations.
- New supplier validation — proving equivalence before switching.
3 LDPE batches · 4 techniques converge, NMR reveals the difference
In semicrystalline polymer systems, thermomechanical processing variables influence chain conformational dynamics¹. Solid-state NMR resolves chemical environments at the nanometer scale², sensitive to changes not detectable by XRD or FTIR³.
Technical justification anchored in the literature
Every technique choice and every inference in the report is backed by peer-reviewed literature — with citations in the text. The conclusion isn't loose opinion: it's a traceable argument, defensible in an audit and in front of the client.
- Numbered citations linking claim to source
- Official standards and methods referenced per analyte
- Auditable reasoning end to end
Conclusion and expert opinion
The report closes with a clear position, signed by the Principal Investigator: what the data shows, what can't yet be claimed, and the next step. It includes an honest caveat on the limits of inference — what separates a technical opinion from a guess.
- Explicit technical position, not just results
- Inference limits declared honestly
- Next-step recommendation signed by the P.I.
Four techniques confirmed equivalence; only the solid-state NMR revealed the subtle conformational change not distinguishable by conventional QC — a molecular signature consistent with the atypical filtration behavior.
Without the industrial line's parameters, no direct causal correlation can be established — a complementary step is recommended for elucidation.
Aplicações de mercado
Onde a FTIR entrega resultados
Market Applications
Pharma
- Impurity and degradant identification
- API identity verification
- Polymorphic form analysis
- Excipient-API compatibility studies
- Enteric coating characterization
Materials
- Polymer identification
- Plastic additive analysis
- Fiber characterization
- Resin curing control
- Oxidative degradation analysis
Cosmetics
- Raw material analysis
- Emulsifier characterization
- Preservative verification
- Fragrance identification
- Natural product analysis
FAQ
Frequently Asked Questions about Fourier Transform Infrared Spectroscopy (FTIR)
What functional groups or bonds can FTIR detect?
- FTIR detects vibrational absorption from bonds such as O-H, N-H, C=O, C-H, C-N and many others, each appearing in a characteristic wavenumber range. This makes it well suited to identifying functional groups present in a molecule and to fingerprinting a compound's overall spectral pattern for identity confirmation.
What is the difference between FTIR-ATR and transmission FTIR?
- ATR (Attenuated Total Reflectance) presses the sample directly against a crystal and requires little to no sample preparation, making it fast and suited to solids, pastes and liquids as-is. Transmission FTIR passes the infrared beam through the sample (often a thin film or a KBr pellet for solids) and can offer better spectral quality for some applications, but requires more preparation.
Can FTIR identify an unknown compound?
- Yes — an FTIR spectrum functions as a molecular fingerprint, and matching it against reference spectral libraries or known standards is a standard way to confirm or determine identity, particularly when combined with the sample's expected functional-group composition.
Can FTIR distinguish between different polymorphic (crystalline) forms of the same compound?
- Often yes — because a molecule's crystal packing can shift or split certain vibrational bands, FTIR can detect differences between polymorphic forms of the same chemical compound, making it a useful complementary technique to X-ray diffraction for polymorph screening and identity verification.
Does my sample need to be dry or in a particular physical state for FTIR?
- FTIR can analyze solids, liquids, pastes, and films, and ATR mode in particular tolerates a wide range of physical states with minimal preparation. Strong water absorption can interfere with some spectral regions in aqueous samples, so sample state and expected interferences are confirmed as part of method selection.
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