Fourier Transform Infrared Spectroscopy – FTIR

Fourier Transform Infrared Spectroscopy

Fourier transform infrared spectroscopy (FTIR) is an optical analytical technique frequently used to identify organic and polymeric compounds in solid, liquid and gaseous samples. It is widely used for gaining structural information of unknown compounds in samples, residue and contaminants analysis, product development, failure analysis, investigative studies, etc.

FTIR uses infrared light to irradiate a sample and polymeric and organic compounds, present in the sample, produce their distinctive fingerprint in the form of an infrared absorption spectrum (interferograms). The FTIR software applies fourier transformations to convert this interferogram to IR spectra that are unique to the various functional groups and chemical bonds present in the sample. Comparing these spectrographs against available databases can give quantitative analysis of the compounds present in the materials.

There are different sampling techniques such as transmission, specular reflectance, diffuse reflectance, and Attenuated Total Reflection (ATR). Specular reflectance is used for both organic and inorganic samples having large, flat, and reflective surfaces. In diffuse reflectance, powder samples are examined in the form of a KBr pellet. In ATR, insoluble, multi-layer, or solid samples are analyzed using hard crystal material.

In order to get over the restrictions imposed by dispersive devices, Fourier Transform Infrared (FT-IR) spectroscopy was created. The lengthy scanning procedure was the biggest challenge. It was necessary to develop a technique for sensing all infrared wavelengths simultaneously as opposed to separately. An interferometer, a very basic optical tool, was used to create a solution.

All of the infrared frequencies are “encoded” into a special kind of signal that the interferometer generates. The measurement time for the signal is typically on the order of one second or less. As a result, the time element per sample is decreased from several minutes to a few seconds.

Infrared spectroscopy now provides a number of important practical benefits thanks to the Fourier Transform Infrared (FT-IR) technology. It has enabled the creation of numerous new sampling approaches that have been intended to solve difficult situations that were insurmountable with earlier technologies. It has almost unlimited the application of infrared analysis.

Video 01: Introduction to Infrared Spectroscopy (IR)

Fourier Transform Infrared Spectroscopy (FTIR) Common Uses

• Determination of water content in thin plastic and composite parts
• Interfacial characterization of rubber nanocomposites
• Indication of a different degree of polymerization (curing) of a sample by recording its deviations from an expected IR spectrum
• Monitoring of oxidation of the aluminium film
• Investigation of proteins in hydrophobic membrane environments
• Quantitative detection of contaminants and additives in the sample induced by handling and processing
• Indication of oxidation and degradation of the sample
• Identifies the presence of organic and inorganic compounds in the sample
• Detection of fillers in the gemstones

Advantages

• Short scan time as all wavelength measurements are performed simultaneously
• Precise and reproducible measurements
• The wavelength scale is calibrated by a HeNe laser, which is stable and accurate – the user does not need to calibrate the instrument
• The detectors are quite sensitive, and the optical throughput is much higher
• Mechanically simple equipment because of only one moving part
• Less interference on the analysis by the stray light

Limitations

• The results remain true if there is no change in atmospheric conditions throughout the experiment
• Several molecules such as water may interfere with the sample analysis as they completely absorb infrared light
• The glass is not an appropriate substrate for FTIR analysis as it absorbs infrared light
• Can not detect atoms or monoatomic ions such as entities that contain no chemical bonds
• Can not detect homonuclear diatomic molecules such as O2, N2, and Cl2
• Some inorganic species exhibit an FTIR spectrum such as silicates, carbonates, nitrates, and sulfates

Industries

• Pharmaceuticals
• Paints, Coatings, and Laminates
• Advanced Materials
• Polymer
• Petrochemical
• Food Testing
• Forensic analysis
• Gemology

Fourier Transform Infrared Spectroscopy (FTIR) Laboratories

• EAG Laboratories, Inc.
• Intertek
• Jordi Labs
• ATS Applied Technical Services, Inc.
• RTI Laboratories
• Laboratory Testing, Inc.
• EMSL Analytical, Inc.
• MVA Scientific Consultants

More Details

• Working principle of FTIR
• Uses of FTIR
• Advantages of FTIR