Molecular features of dissolved HA fractions at different extraction times

J. A. GONZÁLEZ-PÉREZ; M. AVENA; M. BRIGANTE; G. ZANINI; T. VERDEJO; R. GONZÁLEZ-VÁZQUEZ; F.J. GONZÁLEZ-VILA

Lanzarote, Islas Canarias, España.

Simposio; 18th International Symposium on Analytical and Applied Pyrolysis; 2008

Advances in Analytical and Applied Pirolysis

Humic substances (HS), found in all terrestrial and aquatic environments, represent an important and active fraction of the refractory organic matter [1]. Humic substances are operationally defined in terms of their solubility in aqueous media as a function of pH. Humic acid (HA) is the fraction of HS that is soluble at high pH values. The HA was originally extracted and purified from a soil with andic characteristics according to the procedures recommended by the IHSS (elemental composition: N 4.86%, C 52.57%, H 5.06%, O 37.18%, S 0.33%). For detailed information about this HA and dissolution kinetics see Brigante et al. (2007) [2]. Double-Shot Py-GC/MS was used to investigate the molecular features of HA that enters in solution in aqueous media (pH 8.5) at different extraction times. Total desorption (280º C) and pyrolysis (500º C) products (Fig. 1) were analysed in the original HA and in six fractions obtained after re-precipitation of the dissolved HA (pH 1.5). Alkylic (alkane/alkene pairs), aromatic (methyl napthalenes), other polyaromatics (PAHs) and lignin markers (methoxyphenols) were also investigated. Differences were found in the products released by desorption and pyrolysis from the six fractions. It is found that lignin markers are typical desorption products and that the sequential technique used (Double-Shot Py-GC/MS) provide complementary windows of information to elucidate molecular features of complex organic matrices such are HAs References 1.   P. MacCarthy, Soil Sci. 166 (2001) 738. 2.   M. Brigante, G. Zanini, M. Avena, Colloid Surf. A. 294 (2007) 64.