Studies on soil humic compounds, fungal melanins and model polymers by pyrolisis mass-spectrometry

8 pages, 4 figures, 15 references.Biopolymers or synthetic polymers are frequently characterized by pyrolysis in combination with gas chromagraphy, mass-spectrometry or gas chromatography and mass-spectrometry. Curie-point pyrolysis technique in conjunction with low-voltage electron impact ionization mass-spectrometry was used to characterize several soil humus fraction including whole soil, and to compare them with humic acid-like melanins from soil fungi, model phenolic polymers and several biopolymers such as polysaccharides, lignins or proteins. Humic acids from different soil types gave complex pyrolysis spectra. Although the chemical structure of individual compounds cannot be assigned with certainty, the spectra show a marked qualitative and even quantitative correspondence through the presence of similar series of homologous ions. They are probably related to protein-like materials, aromatic and phenolic compounds and to polysaccharides. Similar series were observed in the spectra of whole soil and with humins, but more prominent peaks corresponding to complex polysaccharide materialS were present in addition. Spectra from fulvic acids so far investigated differed largely from those of humic acids, and showed a greater relation to polysaccharides. With some exceptions spectra from humic acid-llke melanins from fungi were similar to those from soil humic acids, and showed a similar series of homologous ions. Model oxidative polymers, prepared by phenolase oxidation of phenols in a neutral buffer medium, with and without the addition of amino acids or a peptide mixture, showed marked differences from melanins and humic acids if only simple phenols together with amino acids were used. However, the spectra became more and more similar to the melanins if a more complex phenol mixture was oxidized together with a complex peptide mixture. Most soil humic acids or even soil showed in addition ion series with characteristics of lignin-type phenols. However, these were in general weak signals or sometimes absent.Peer reviewe