Methods / ATR-FTIR

ATR-FTIR analysis

Attenuated total reflectance (ATR) is a popular FTIR spectroscopy sampling technique that enables fast characterization of various sample types with minimal preparation. ATR-FITR is utilized widely in industries including polymers, pharmaceuticals, food, and fuels.

FTIR-ATR
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What is ATR-FTIR used for?

ATR-FTIR is used in various research areas and industries. Examples of applications include material identification in the plastics industry, pharmaceutical industry quality control, and protein analysis in biological research. The method is also used for chemical characterization in industries including consumer goods, food, fuels, and biorefinery.

One increasingly popular application of ATR-FTIR is identifying microplastics released from textiles during laundering. The analysis can be supplemented with the SEM-EDX method to obtain further information on the identified particles.

How does attenuated total reflection work?

The ATR-FTIR apparatus consists of an infrared light source, a detector, and a crystal with a high refractive index, such as diamond, germanium, or zinc selenide. The sample is placed on the crystal and infrared light is directed at it. The light passes through the crystal and reflects at the crystal-sample interface, where it partially penetrates the sample, creating an evanescent wave.

Some of the light is absorbed within the evanescent wave, which means that the reflected light now carries information about how the sample absorbs IR radiation. The reflected light passes to the detector, allowing an FTIR-ATR spectrum to be produced. When compared with a library of known spectra, the obtained spectrum can help identify the sample's chemical composition.

ATR-FTIR diagram
A simplified diagram of a single-reflection ATR-FTIR setup.

The advantages of ATR in FTIR sampling

ATR allows for various sample types, including liquids, solids, powders, and solutions, to be tested whilst yielding consistent, reproducible results. It generally requires very little sample preparation compared with other forms of FTIR and only requires a small amount of sample to produce high-quality results. In most cases, the sample can be recovered after analysis.

Single-reflection vs. multi-reflection ATR sensors

In single-reflection ATR-FTIR analysis, the infrared light is reflected from the surface boundary a single time before being detected. Multi-reflection ATR sensors have a larger crystal which allows the light to reflect multiple times before being detected. The benefit is increased sensitivity for particularly weak absorbances, making multi-reflection sensors ideal for harder-to-detect chemical groups and for testing low-concentration solutions.

Suitable sample matrices

  • Powders
  • Solid objects
  • Liquids
  • Solutions

Ideal uses of FTIR-ATR

  • Identification of unknown compounds
  • Quality control of consumer goods
  • Biological research
  • Microplastic identification

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Frequently asked questions

What is ATR-FTIR analysis used for?

ATR-FTIR can be used to analyze the chemical composition of solid and liquid sample materials, including polymers, pharmaceuticals, fuels, and food.

What are the advantages of ATR-FTIR?

The ATR-FTIR setup yields consistent, reliable, and comparable results quickly with little to no sample preparation.

What is Measurlabs?

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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