The sodium-amalgam reduction of soil and fungal humic substances

Two soil humic acids and a “humic acid” synthesized in the laboratory by Stachybotrys chartarum were reduced with Na-amalgam. The reduction products were methylated, separated by preparative gas chromatography and identified by matching their mass and micro-infrared spectra with those of authentic specimsens.Yields of reduction products identified ranged from 2.7 to 4.2% of the initial weights of the humic materials. Major products identified were N-methyl-benzylsulfonamide, methylated phenolic acids, aromatic aldehydes and C₆C₂ - and C₆C₃ - compounds with 0 in the side chains. Since the Na-amalgam reduction of both soil and fungal humic materials produces the same or similar compounds, the method provides little information on the origin of these compounds, that is, whether they are lignin- or flavonoid-derived or synthesized by microorganisms. Compared with oxidative degradation methods, Na-amalgam reduction appears to be inefficient and tells little about the chemical structure of humic acid polymers.