---
title: "Fourier-transform infrared spectroscopy"
chunk: 5/5
source: "https://en.wikipedia.org/wiki/Fourier-transform_infrared_spectroscopy"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:41:27.177904+00:00"
instance: "kb-cron"
---

=== Microscopy and imaging ===
An infrared microscope allows samples to be observed and spectra measured from regions as small as 5 microns across. Images can be generated by combining a microscope with linear or 2-D array detectors.  The spatial resolution can approach 5 microns with tens of thousands of pixels.  The images contain a spectrum for each pixel and can be viewed as maps showing the intensity at any wavelength or combination of wavelengths. This allows the distribution of different chemical species within the sample to be seen. This technique has been applied in various biological applications including the analysis of tissue sections as an alternative to conventional histopathology, examining the homogeneity of pharmaceutical tablets, and for differentiating morphologically-similar pollen grains.

=== Nanoscale and spectroscopy below the diffraction limit ===
The spatial resolution of FTIR can be further improved below the micrometer scale by integrating it into scanning near-field optical microscopy platform. The corresponding technique is called nano-FTIR and allows for performing broadband spectroscopy on materials in ultra-small quantities (single viruses and protein complexes) and with 10 to 20 nm spatial resolution.

=== FTIR as detector in chromatography ===
The speed of FTIR allows spectra to be obtained from compounds as they are separated by a gas chromatograph. However this technique is little used compared to GC-MS (gas chromatography-mass spectrometry) which is more sensitive. The GC-IR method is particularly useful for identifying isomers, which by their nature have identical masses. Liquid chromatography fractions are more difficult because of the solvent present.  One notable exception is to measure chain branching as a function of molecular size in polyethylene using gel permeation chromatography, which is possible using chlorinated solvents that have no absorption in the area in question.

=== TG-IR (thermogravimetric analysis-infrared spectrometry) ===
Measuring the gas evolved as a material is heated allows qualitative identification of the species to complement the purely quantitative information provided by measuring the weight loss.

=== Water content determination in plastics and composites ===
FTIR analysis is used to determine water content in fairly thin plastic and composite parts, more commonly in the laboratory setting. Such FTIR methods have long been used for plastics, and became extended for composite materials in 2018, when the method was introduced by Krauklis, Gagani and Echtermeyer. FTIR method uses the maxima of the absorbance band at about 5200 cm−1, which correlates with the true water content in the material.

== See also ==
Discrete Fourier transform – Function in discrete mathematics − for computing periodicity in evenly spaced data
Fourier transform – Mathematical transform that expresses a function of time as a function of frequency
Fourier transform spectroscopy – Spectroscopy based on time- or space-domain dataPages displaying short descriptions of redirect targets
Least-squares spectral analysis – Periodicity computation method − for computing periodicity in unevenly spaced data

== References ==

== External links ==
Infracord spectrometer photograph
The Grubb-Parsons-NPL cube interferometer Spectroscopy, part 2 by Dudley Williams, page 81
Infrared materials Properties of many salt crystals and useful links.
University FTIR lab example Archived 2017-01-10 at the Wayback Machine from the University of Bristol