Fourier Transform Infrared Spectroscopy for Material Identification
Fourier Transform Infrared Spectroscopy (FTIR Analysis or FTIR Spectroscopy) is an analytical technique used to identify organic, polymeric, and in some cases, inorganic materials. The FTIR analysis method uses infrared light to scan test samples and observe chemical properties. During FTIR analysis, an absorbance spectra of the sample is created which provides information about the unique chemical bonds and molecular structure of the material. This profile is in the form of an absorption spectrum which shows peaks representing components in higher concentration. Different types of bonds, and thus different functional groups (e.g. alkanes, ketones, acid chlorises), absorb infrared radiation of different wavelengths. Although the analysis is performed in absorbance, it can be converted to transmittance, since they are simply the inversions of each other.
Fourier Transform Infrared Spectroscopy is extremely useful for assessing purity and identifying base polymer composition, additives, organic contaminants and the general types of materials being analyzed when there are unknowns. Both quantitative and qualitative information can be provided about the test sample. Samples in a variety of forms can be analyzed by the FTIR spectroscopy method:
- Solids placed on a crystal
- Liquids placed between two sodium chloride plates
- Thin film placed in a cassette
- Powdered sample mixed with potasium bromide and placed in a pellet
Laboratory Testing Inc. performs FTIR analysis with a high-tech Thermo Scientific Nicolet iS10 FT-IR spectrometer. FTIR spectroscopy compliments the wide-range of instrumental and wet chemistry services performed at LTI for materials characterization and failure analysis. In addition to identification of polymers by FTIR, qualitative and quantitative element analysis, even at trace levels, is available for a variety of materials including metals, powdered metals, ores, ferroalloys, composites and ceramics. Laboratory Testing Inc. is fully capable of preparing test specimens for all analysis.
The Test Process
FTIR analysis can be accomplished by Attenuated Total Reflectance (ATR), Nujol and thin film. Enough sample is required to obtain an absorption spectrum during FTIR analysis. Solid samples are usually prepared by shaving some material off of the sample that is thin enough to obtain a good spectrum.
The first step is to collect a background spectra to subtract from the test spectra to ensure the actual sample is all that is analyzed. Next, the sample is analyzed by LTI’s fully-computerized Fourier Transform Infrared Spectroscopy system which generates the spectrum showing the molecular structure of the sample material. Absorbance peaks on the spectrum indicate functional groups. The analytical spectrum is then compared in a reference library program with cataloged spectra to identify components or to find a “best match” for unknown material using the cataloged spectra for known materials. See the process in our FTIR Analysis Video:
- Identification of organic, polymeric, and in some cases, inorganic materials including sample composition, additives, contaminants and unknown materials
- Library of reference spectra