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UV-VIS-NIR absorption spectroscopy

The spectral infos contained in the ultraviolet, visible and near-infrared (UV-VIS-NIR) bands identify the intrinsic composition of a liquid, and allows for discriminating among similar liquids. In particular, the UV band is specific for the electronic transitions, while the VIS band contains infos about  pigments and chromophores. Although the true fingerprinting region is the mid-infrared, also the NIR iis advantageously used, as it includes overtones of MIR bands and some of their combinations.

Absorption spectroscopy is conveniently performed in the wide UV-VIS-NIR spectral range by means of optical fibers, as they are transparent from 200 to 2500 nm. The wide availability of bright LEDs and compact/portable spectrometers, further enhance the application areas of absorption spectroscopy, and make it possible the implementation of compact instrumentation dedicated to the monitoring of specific parameters.

We have used optical fibers and low-cost spectrometers and sources to perform UV-VIS-NIR absorption spectroscopy with a  test case liquids, that is the extra virgin olive oils. The measured hyperspectral signatures are processed by means of multivariate analysis with the twofold scope to achieve classification maps and also the correlation with important chemo-physical parameters.

A hyperspectral optical signature describing the intrinsic identity of a liquid

Typical set up for UV-VIS-NIR

absorption spectroscopy performed by optical fibers

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Extra virgin olive  oils — crop 2005/2006

  From the hyperspectral optical signature:

1) to the classification according to the geographic area of origin

2) To the correlation with fatty acids, the most important nutritional factors of olive oil

See more:

SPIE vol. 6585, 2007, pp. 65852C-1/C-6