Middle infrared (ATR FT-MIR) characterization of industrial tannin extracts

In the present paper a detailed investigation of the molecular vibrations of eight industrial tannin powder extracts is presented. The ATR FT-MIR spectra observed in the spectral window between 1800 and 600 cm(-1) allow specific band profiles to be identified which are typical for the various hydroxyl-aromatic molecules that constitute the tannin extracts. Hence, it was possible to rapidly discriminate the two main families of tannin. The hydrolysable tannins show intense absorptions in the region of the C=O at around 1700 cm(-1) and also two major single bands at around 1315 and 1180 to be assigned to aromatic C-O. Conversely, the flavonoids of the condensed tannins present an overall structured profile especially in the region between 1400 and 1100 cm(-1). Spectra of tannin extract with intermediate profiles were also registered and chemometric tools such as the principal components and cluster analysis showed a noticeable potential for determining the nature of the extracts. (C) 2014 Elsevier B.V. All rights reserved.