Regular papers

Optical spectral signatures of liquids by means of fiber optic technology for product and quality parameter identification

¹ CNR-IFAC, Sesto Fiorentino (FI), Italy
² Dpto. Óptica, Universidad Complutense de Madrid – Madrid, Spain
³ Photonics Engineering Group, Universidad de Cantabria – Santander, Spain
⁴ Department of Applied Physics and Photonics, Vrije Universiteit Brussel – Brussel, Belgium
⁵ CNR-IVALSA, Sesto Fiorentino (FI), Italy
⁶ MECOIL Diagnosi Meccaniche srl, Firenze, Italy
⁷ Dipartimento di Fisica and LENS, Universitá di Firenze – Sesto Fiorentino (FI), Italy

^* a.g.mignani@ifac.cnr.it

Received: 8 January 2009

Abstract

Absorption spectroscopy in the wide 200–1700 nm spectral range is carried out by means of optical fiber instrumentation to achieve a digital mapping of liquids for the prediction of important quality parameters. Extra virgin olive oils from Italy and lubricant oils from turbines with different degrees of degradation were considered as ’case studies’. The spectral data were processed by means of multivariate analysis so as to obtain a correlation to quality parameters. In practice, the wide range absorption spectra were considered as an optical signature of the liquids from which to extract product quality information. The optical signatures of extra virgin olive oils were used to predict the content of the most important fatty acids. The optical signatures of lubricant oils were used to predict the concentration of the most important parameters for indicating the oil’s degree of degradation, such as TAN, JOAP anti-wear index, and water content.