Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy of functional groups of humic acid dissolving in aqueous solution

Tanaka, Tadao; Nagao, Seiya; Ogawa, Hiromichi

Analytical Sciences (CD-ROM), 17(Suppl.), p.1081 - 1084, 2002/03

Structural information of humic acid dissolving in aqueous solution has been studied by ATR-FTIR spectroscopy. Two types of humic acid fractions were prepared: one is dominated by aliphatic structure and another is dominated with aromatic structure. The functional groups of both fractions have been characterized with respect to their ATR-FTIR spectral structures (ATR spectra) measured in pH range of 2 - 10. The ATR spectra were compared with the infrared spectra of the freeze-dried humic acid fractions, which were obtained using transmission Fourier transform infrared spectroscopy with KBr pellet (KBr spectra) and using diffuse reflectance infrared Fourier transform spectroscopy (DRS spectra). In a comparison between spectra obtained from the three infrared spectroscopic methods, the major absorptions of the ATR spectra for both fractions are in well agreement with those of the KBr spectra and the DRS spectra, each other. These show that the functional groups of the humic acid dissolving in aqueous solution could characterize by using the ATR-FTIR spectroscopy.