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Portable NIR sensors in medicinal plant quality control

In the quest for fast and reliable ingredient analysis, Christian W Huck, Krzysztof B Bec and Justyna Grabska from the Institute of Analytical Chemistry and Radiochemistry at the University of Innsbruck, consider the use of portable NIR spectroscopy, comparing the results from standard and miniaturised sensors.

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To ensure quality from the start, beginning with plant breeding on the field and continuing through the extraction and production process, requires fast analytical techniques that can record multiple chemical and physical datapoints simultaneously. For this purpose, near-infrared (NIR) spectroscopy has shown great aptitude for more than two decades.1 Since the first appearance of a portable spectrometer, NIR sensors have demonstrated several advantages over others, including fluorescence, laser-induced breakdown spectroscopy, mass spectrometry (MS) and nuclear magnetic resonance (NMR). Recent years have brought ultra-miniaturised NIR spectrometers to fruition, working with either USB power or a built-in battery at a weight of less than 50g, making installation in drones and smart phones a reality2 (Figure 1). Nowadays, those systems can also be operated by non-experts supported by sophisticated software. Searching for “portable NIR spectroscopy” on the ISI Web of Science database results in more than 1,400 publications and 20,000 citations since 2005. Individual miniaturised NIR sensors work with different light sources, wavelength selectors, optical materials and detectors,3 facilitating the analysis of chemical, physical and other properties of the material under investigation.