Fourier transform infrared spectroscopy (FTIR) is an analytical technique used to identify the functional groups of a molecule. FTIR analysis is suitable for liquids, solids, and gases with covalent bonds.
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What is FTIR spectroscopy used for?
FTIR is an effective analytical tool for material identification. Some of the most common applications include identifying chemical components in solid and aqueous matrices. FTIR can also be used to identify microplastics in water samples. The results will yield the number of particles by plastic type and size range.
The operating principle of FTIR
During FTIR analysis, the material (solid, liquid, or gas) is subjected to an infrared light spectrum. When different molecules absorb IR light, molecular vibration occurs. Different molecules and bonds vibrate in a way characteristic to them, leading to different amounts of light being absorbed at specific wavelengths depending on the sample's composition.
The amount of IR light that passes through the sample is measured with a detector and the data is converted to a spectrum-friendly form via a mathematical process called Fourier transform. The final spectrum represents light intensity as a function of wavenumber.
Advantages of FTIR compared to traditional IR spectroscopy
FTIR allows precise and simultaneous spectral data collection with a wide spectral range, made possible by fixed and movable mirrors in the interferometer. The broad spectral range allows multiple frequencies of light to be directed at the sample at once, making FTIR more effective time-wise when compared to a traditional dispersive IR spectroscopy technique. FTIR also has a higher signal-to-noise ratio and high wavelength preciseness, making it more accurate than conventional IR spectroscopy.
Often, FTIR measurement does not require any sample preparation, especially when using the ATR-FTIR setup. Tricky samples can be ground with IR transparent potassium bromide (KBr) and pressed into a pellet form. Liquids can either be measured directly, or an IR transparent solvent can be used to prepare a dilution. Gas samples are placed in a cylinder-shaped cell with IR-transparent windows.
Suitable sample matrices
- Liquid, solid and gaseous materials
- Organic materials, such as plastic, paper, cardboard, biomass and solvents
- Inorganic compounds that absorb IR light
Ideal uses of FTIR
- Identification of functional groups
- Identification of unknown materials
- Comparing the chemical composition of different chemicals and materials
Frequently asked questions
This technique is used to identify the functional groups present in the sample. FTIR is suitable for the identification of polymeric materials and for comparing the chemical composition of different chemicals and materials.
Metals do not absorb light in the IR range and are therefore not suitable for FTIR spectroscopy. Complex molecules and their mixtures cannot be reliably identified. FTIR also cannot detect diatomic or noble gases, such as N2 or He.
FTIR spectroscopy is suitable for solids, liquids and gases.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
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