Determination of Water in Lubricating Oils by Mid- and Near-Infrared Spectroscopy

Marcelo Blanco, Jordi Coello, Hortensia Iturriaga, Santiago Maspoch, Ramón González

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25 Citations (Scopus)


Mid-infrared (MIR) and near-infrared (NIR) spectroscopy were used to determine water in lubricating oils with high additive contents that introduce large errors in determinations by the Karl-Fischer and hydride methods. MIR spectra were obtained in the attenuated total reflectance (ATR) mode and exhibited water specific band absorption in the region 3100-3700cm-1, which facilitated calibration. Multivariate (partial least-squares regression, PLSR) and univariate calibration (based on peak height and band area as independent variables) were tested. Both led to errors of prediction less than 5%. NIRS determinations rely on absorbance and first-derivative spectra, in addition to two different types of multivariate calibration, viz. inverse multiple linear regression (MLR) and partial least-squares regression (PLSR). Both approaches gave similar results, with errors of prediction less than 2%. For none of the proposed approaches any sample pretreatment for recording spectra is required.
Original languageEnglish
Pages (from-to)235-239
JournalMikrochimica Acta
Issue number3--4
Publication statusPublished - 1 Dec 1998


  • FTIR
  • Lubricating oils
  • Multivariate calibration
  • NIR
  • Water determination


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