Introduction to FTIR spectroscopy
FTIR spectroscopy offers a vast array of analytical opportunities in academic, analytical, QA/QC and forensic labs. Deeply ingrained in everything from simple compound identification to process and regulatory monitoring, FTIR covers a wide range of chemical applications, especially for polymers and organic compounds. Learn more about the basics and the value of this popular technique by watching the tutorials below. Videos also provide an overview of two common detectors and the apodization function.
FTIR stands for Fourier transform infrared, the preferred method of infrared spectroscopy. When IR radiation is passed through a sample, some radiation is absorbed by the sample and some passes through (is transmitted). The resulting signal at the detector is a spectrum representing a molecular ‘fingerprint’ of the sample. The usefulness of infrared spectroscopy arises because different chemical structures (molecules) produce different spectral fingerprints.
So, what is FTIR?
- The Fourier Transform converts the detector output to an interpretable spectrum.
- The FTIR generates spectra with patterns that provide structural insights.
Watch the tutorial for a quick description of what "FTIR" means and how the "FT" and the "IR" parts work together.
The FTIR uses interferometry to record information about a material placed in the IR beam. The Fourier Transform results in spectra that analysts can use to identify or quantify the material.
- An FTIR spectrum arises from interferograms being ‘decoded’ into recognizable spectra
- Patterns in spectra help identify the sample, since molecules exhibit specific IR fingerprints
Watch the tutorial for a closer look at the heart of the FTIR and a brief examination of why it is so popular as a tool.
FTIR sampling introduction
There are four major sampling techniques in FTIR:
- Attenuated Total Reflection (ATR)
- Specular Reflection
- Diffuse Reflectance
Each technique has strengths and weaknesses which motivate their use for specific samples
Watch the tutorial for a short look at the four main ways samples are examined in FTIR.
Sampling and applications of FTIR
FTIR can be a single purpose tool or a highly flexible research instrument. With the FTIR configured to use a specific sampling device – transmission or ATR for instance – the spectrometer can provide a wide range of information:
- Most commonly, the identification of an unknown
- Quantitative information, such as additives or contaminants
- Kinetic information through the growth or decay of infrared absorptions
- Or more complex information when coupled with other devices such as TGA, GC or Rheometry
Ultimately, FTIR can be a cost-effective answer machine.
Watch the tutorial for a more extensive examination of FTIR sampling techniques, including hyphenated sampling. Examples are shown and discussed giving an overview of what is possible.
Featured FTIR detector videos
The professor provides an overview of two common FTIR detectors, DTGS and MCT, to help you choose the right detector for your FTIR applications.
Now go into the lab and see a demonstration of the DTGS and MCT detectors.
Featured FTIR apodization videos
The professor provides an easy-to-understand overview of apodization, a mathematical function applied to the FTIR spectrum.
Now go into the lab to see the effects of apodization applied to the FTIR spectrum.
Dr. Michael Bradley received his B.S. degree in Chemistry from the University of South Carolina and his Ph.D. in Physical Chemistry from the University of Illinois, and also completed his MBA in management. He taught graduate and undergraduate chemistry for 15 years, prior to becoming a field applications scientist with Thermo Nicolet, subsequently Thermo Fisher Scientific, in 2002.
Functional groups are structural units within organic compounds defined by specific atom and bond arrangements. Infrared is a powerful identification tool for functional groups because of the similar absorption frequencies for those groups in different molecules. The actual frequency is affected by the environment, so the reference chart shows wide bands rather than specific frequencies. The identification of functional groups is a cornerstone of IR spectroscopy and organic chemistry.
Flexible FTIR spectrometers – like the Thermo Scientific Nicolet iS 50 FTIR Spectrometer – can be configured to cover a wide range of performance. A part of this is spectral range as shown in this chart, where certain combinations of components provide high performance in specific ranges. There are often trade-offs, such as between high sensitivity using an MCT-A liquid-nitrogen cooled detector versus the wider spectral range but lower sensitivity of the DLaTGS room temperature detector.
Access a targeted collection of application notes, case studies, videos, webinars and white papers covering a range of applications for Fourier Transform infrared spectroscopy, Near-infrared spectroscopy, Raman spectroscopy, Nuclear Magnetic Resonance, Ultraviolet-Visible (UV-Vis) spectrophotometry, X-Ray Fluorescence, and more.