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Small spectrometer with a big future

In a raid the police seize some suspicious white powder. But is it really a narcotic substance? Previously the powder would have had to be sent to a laboratory for testing. A portable infrared spectrometer now enables the analysis to be conducted on site.

Do the tablets contain enough or possibly even too much active agent? Is the medicinal yield from the raw materials adequate or are the waste products excessive? Producing pharmaceuticals and chemicals in large quantities is a complex process which has to be constantly monitored – for example using spectrometers. The principle is as follows: The tablets or other solid items are radiated with light and the spectrometers measure how much light of a certain wavelength is reflected by the sample. In the case of liquids and gases the device analyzes how much light permeates the sample. These measurements permit conclusions to be drawn on the composition of the samples, for instance the amount of active agent in tablets. Current spectrometers are large and expensive, which means that in industrial processes they can only be deployed at certain points along the production chain. Working in cooperation with colleagues at Chemnitz University of Technology and an industrial company, COLOUR CONTROL Farbmess-technik GmbH, research scientists at the Fraunhofer Institute for Reliability and Microintegration IZM have developed a portable infrared spectrometer which is now being marketed by COLOUR CONTROL. “It’s about a quarter of the cost of conventional spectrometers,” says Dr. Thomas Otto, deputy head of department at the IZM in Chemnitz. What’s more, measuring 10 x 6 x 8 centimeters, it is scarcely bigger than a packet of soap, whereas comparable devices have up to now been more like the size of a suitcase. “The key part of the development is a movable micro-mirror which precisely deflects the infrared radiation,” says Otto. “As the mirror can be tilted, it can deflect the light in various directions. This enables it to replace two quite large hollow mirrors.” A chromium and gold coating on the mirror ensures that more than 98 percent of the light is reflected. The small spectrometer has many potential applications. It could help the police to classify narcotics during raids and to determine the content of active substance. Such tests have had to be conducted in special laboratories up to now. “In the production of solar cells too, the spectrometer can do a good job in combination with an ellipsometer for determining layer thicknesses. Manufacturers can check whether the individual solar cell layers possess the right thickness and the desired properties,” says Otto. The spectrometer is so small that it can be integrated in the ellipsometer instead of taking up nearly as much room as a suitcase.


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