The diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectrum of the peeled wood of kenaf (Hibiscus cannabinus L.), cotton (Gossypium barbadense), and pine (Pinus brutia) revealed three broad absorptions in the region of 1800-1540 cm-1. The deconvolution of spectra in this region revealed the existence of 10 major peaks contributing to that spectrum in the aforementioned region. The absorption peaks at 1710 and 1608 cm-1 have been assigned to carboxylic (-COOH) and carboxylate (-COO-) groups, respectively. Since their relative size is pH dependent, the ratio of their area was used as a pH indicator. A linear relationship was then established between that ratio and the amount of acid need to bring the pH of the wood to 3, as it is measured by the pH determination of a water extract of the wood. This is the pH at which the wood is processed during manufacturing of chipboards.
C. Pappas, P. Rodis, P. A. Tarantilis, and M. Polissiou, "Prediction of the pH in Wood by Diffuse Reflectance Infrared Fourier Transform Spectroscopy," Appl. Spectrosc. 53, 805-809 (1999)