Infrared spectroscopy applications

Where can infrared technology be used?

The technology can be used in a very broad range of applications.  Applications can for instance range from environmental monitoring (exhaust gas inspections), to production (chemical process controls, surface thickness measurements), the recycling field (plastic identification, construction debris sorting, carpet recycling), the food industry (meat), agriculture (protein content of grain) and medical care (body fat),  and also including the consumer goods field.

Our objective is to identify new applications and to replace conventional AT-Line analytics with fast and accurate low-cost sensor technology.



Exhaust gas inspections with infrared sensor technology

Infrared analysis has been used for gas detection applications for quite some time, primarily to measure carbon dioxide and hydrocarbons. This facilitates measuring the concentration of vehicle exhaust gas content directly above the road surface.

The technology can also be used in industrial applications to monitor exhaust gases in smokestacks.

Compound identification of plastics by means of NIR sensor technology

Near infrared spectroscopy is ideally suited for contactless identification of plastics, for high throughput preferably on conveyor belts.

Such a system for grade specific identification of plastics from household waste (keywords: “Yellow Bag”, ” Green Dot”), was already developed by us in 1995 as part of our activities at the Institute for Chemical and Biosensor Technology in Münster, and successfully integrated into a recycling plant. The system is capable of differentiating and sorting plastics, such as PP (Polypropylene), PET (Polyethylenterephthalate), PE (Polyethylene), PS (Polystyrole). Multiplexing is used to monitor up to 8 conveyor belts with one spectrometer system.

However, NIR technology is not only capable of differentiating household plastics, but also all plastics that were not blackened by soot. Near infrared spectroscopy cannot be used for black plastics since too much of the radiation is absorbed. The medium range IR spectrum must be employed to identify black plastics. AOTF technology is used in order to conduct contact-free measurements in these cases. We presented such a system for compound identification of black plastic at the Hanover trade fair in 2000.

Quality control on meat using infrared sensor technology

Fat, protein, and water content are important parameters when assessing the quality of foods. Near infrared spectroscopy is an outstanding tool for determining these compounds. Contact-free measurement is an enormous benefit in this case under hygiene considerations. The range of foods that can be inspected is unimaginably large; examples of existing applications are the determination of milk fat content, the sugar content of fruit, the quality of frying oil, the water content of baked goods, and monitoring the alcohol content during the fermentation process.

Quality control on grain using infrared spectroscopy

Grain analysis paved the way for near infrared spectroscopy to gain widespread acceptance. Measuring the reflection spectrums is an outstanding method for determining fat, protein, water, and fiber content. In addition to stationary measurements, determining these parameters directly on-site is increasingly gaining in significance.

Other applications include measuring the oil content on oil plants, the ripeness of melons, the quality of cotton, or the starch content of potatoes.

Measuring body fat content using infrared spectroscopy

An example for medical applications of NIR spectroscopy is determining the fat content in muscle tissue. Applications can also be found in other areas of medical diagnostics, for instance when determining cholesterol deposits in blood vessels, or for the noninvasive determination of glucose in blood, however, in this case a complete breakthrough has not yet been accomplished.
However we are currently looking for partners to implement an unconventional idea to address the problem of inadequate accuracy during glucose determination.


The general trend

is towards low-cost portable devices as a supplement or even replacement of elaborate spectrometry systems. While a wide range of filter-based portable devices are available, the information provided by certain wavelengths is typically only adequate for a limited number of applications. The examples above show that a number of uses are now possible that were inconceivable only a few years ago.

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