The aim of this work was to determine Fulvic Acids (FAs) in sediments to better know their composition at the molecular level and to propose substructures and structures of organic precursors. The sediment samples were obtained from a priority area for the conservation of ecosystems and biodiversity in Mexico. FAs were extracted and purified using modifications to the International Humic Substances Society method. The characterization was carried out by 1D and 2D nuclear magnetic resonance (NMR) and high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) in positive (ESI+) and negative (ESI−) modes. Twelve substructures were proposed by the COSY and HSQC experiments, correlating with compounds likely belonging to lignin derivatives obtained from soils as previously reported. The analysis of spectra obtained by HPLC-ESI-MS indicated likely presence of compounds chemically similar to that of the substructures elucidated by NMR. FAs studied are mainly constituted by carboxylic acids, hydroxyl, esters, vinyls, aliphatics, substituted aromatic rings, and amines, presenting structures related to organic precursors, such as lignin derivatives and polysaccharides.

Ultrasound-assisted pretreatment under mild operating conditions has been investigated for intensification of delignification to facilitate the obtaining of ethyl levulinate from biomass. The effect of pH (2 -12), temperature (30˚C -70˚C) and pretreatment time (0 -120 minutes) has been studied for different biomass samples. The most favorable conditions were basic pH, temperature of 70˚C and pretreatment time of 2 h, obtaining values of delignification near 80 percent. The ethyl levulinate is obtained in microwave directly via from samples before and after delignification and analyzed for GC-MS. The results evidenced better yields for the delignified samples.

The chemical composition of n-hexane extractives from lignocellulose residual contained in different agroindustrial wastes was studied. The n-hexane extract, which accounted for 1.6% of total lignocellulose residual weight, was analysed by 1 H-NMR and gas chromatography/mass spectrometry. The most predominant compounds identified were aliphatic hydrocarbons (lineal alkanes, branched alkanes, alkenes). Additionally, terpenes, ketones, fatty alcohols, fatty acids and steroids were also found together in minor amounts. The lipophilic compounds in n-hexane extracts in three lignocellulosic wastes, which is highly valuable information for a more complete industrial utilization of these lignocellulosic materials.