Pyrolysis-gass chromatography-mass spectrometry of soil humic fractions: II. The high boiling point compounds

Pyrolysis-gas chromatography-mass spectrometry studies of soil fulvic and humic acids were made. The high boiling point compounds produced by pyrolysis were separated in a column packed with Chromosorb AW DMCS 80-100 mesh coated with 10% FFAP. Humic acids with a high nitrogen content yielded a complex variety of protein derivatives, such as alkylpyridines, alkylpyrroles, alkylbenzonitriles, indoles, piperidines, pyrazines, and pyrrolidones. Humic acids with low N content yielded a smaller number of heterocyclic nitrogen compounds. Lignin derivatives were also identified, but the amount varied in different samples. Furanes were not as prominent as protein and lignin fragments. Acid hydrolysis released proteins, polysaccharides, and lignins, which could be considered as companion materials of a humic "core". The majority of the pyrolysis compounds from the residue after hydrolysis were identified as alkylbenzenes, alkylnaphthalenes, phenols, benzofuranes, indenes, and fluorenes. Alkanes and alkenes were noted in trace amounts. Pyrolysis behavior of fulvic acids differed from that of humic acids. They produced poorly resolved pyrograms with smaller number and a lower intensity of peaks, from which only furfurals, phenols, benzofuranes, and naphthalenes could be identified.