Infrared spectroscopy

What is infrared spectroscopy used for?

IR spectroscopy is commonly used in pharmaceuticals and other consumer industries to quickly test samples for unwanted contaminants. Infrared spectroscopy is also used across all biochemical industries, ranging from medical to food, to test for selected proteins and other organic compounds.

How does infrared spectroscopy work?

In its simplest terms, IR spectroscopy works by passing a beam of infrared light through a sample. When the beam interacts with different chemical species in the sample, it will provide enough energy to cause the bonds in those molecules to vibrate in a variety of different ways. Some might stretch, bend or even rock very rapidly. Portions of the infrared spectrum are absorbed during this process, with each absorbance corresponding to a specific type of bond and movement.

By measuring the infrared light transmitted through the molecule and taking notes of the sections of the spectrum that are absorbed, it is possible to determine which bonds are present. This provides key information about the chemical structure of the sample.

Sample requirements and preparation

IR spectroscopy can be performed on solids, liquids, and solutions, provided they are of a high enough purity. If the sample is to be tested in solution, care must be taken to ensure the solvent does not absorb infrared energy in the same region as the sample, as this may mask important information. Solid samples can be crushed into fine powder to achieve the best results.

Advantages and limitations of IR spectroscopy

Possibly the greatest advantage of IR spectroscopy is its speed. Analysis can be performed very quickly, leading to high throughput and allowing for several samples to be tested in quick succession. The wide range of suitable sample types also makes infrared spectroscopy incredibly versatile. Finally, IR is a non-destructive technique, meaning the sample is not harmed and can often be recovered afterward.

The main limitation of IR spectroscopy is its inability to provide full structural information in the way that techniques like NMR and mass spectrometry can. Therefore, IR must sometimes be used in conjunction with other techniques. Another downside is that any impurities, including water, can cause unwanted peaks to appear in the data that can mask valuable information.

What is the difference between IR and FTIR?

Fourier Transform Infrared Spectroscopy (FTIR) is a more advanced form of infrared spectroscopy. In FTIR, IR light is reflected from a series of mirrors as it passes through the sample, allowing the light to interfere with itself. The mirror then moves, allowing a spectrum of data points to be collected. This produces a new set of data which, when passed through a data processing technique called a Fourier Transform, will provide a new spectrum for the sample.

These days, the majority of IR testing that is performed is in fact FTIR, as it offers a higher signal-to-noise ratio, accuracy, and speed. 

Need an IR analysis? 

Measurlabs offers high-quality IR spectroscopy analyses for all industries. Check out our total organic carbon determination with IR and identification of chemical groups for aqueous and solid samples. If you wish to discuss your testing needs in more detail, do not hesitate to contact our experts using the form below.