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

Congreso; 18th International Symposium on Analytical and Applied Pyrolisis; 2008

Instituto de Recursos Naturales y Agrobiologia de Sevilla (IRNAS-CSIC)

Humic substances (HS), found in all terrestrial and aquatic environments, represent an important and active fraction of the refractory organic matter. 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%). 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 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.