03387naa a2200229 a 450000100080000000500110000800800410001902400520006010000130011224502140012526000090033952026370034865000140298565000150299965000110301465000090302565300090303465300150304370000190305870000200307777300600309721507782023-03-24       2023    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1007/s11368-022-03390-x2DOI1 aSONG, G.  aVindication for uses of urea-amended aqueous alkali and of concentrated H2SO4-amended DMSO in an exhaustive extraction sequence for the isolation of humic and of humin components of SOM.h[electronic resource]  c2023  aA combination approach of urea-amended aqueous base and H2SO4-amended dimethyl sulfoxide (DMSO) was recently developed in our laboratories to extract the most refractory soil humin fractions. With this approach, up to 95% of the humified soil organic matter (SOM) could be isolated. However, it is still not fully known whether the uses of these amended solvent systems will alter the compositions or structures of the humic fractions isolated. Commercially available lignin and cellulose products were selected as humic-related model compounds with possible contributions to the compositions of soil humin. These were subjected to extraction sequences with solvents (6 M urea + 0.1 M NaOH and DMSO + sulphuric acid (94:6, v/v), respectively) used in our studies for the isolation and characterisation of soil humin. Spectroscopic comparisons (FTIR and 13C NMR) were carried out to investigate their compositional differences before and after treatment with the solvents. Furthermore, soil humic acids extracted in a basic solution and a humic acid-like fraction extracted in urea-amended aqueous base were compared for their similarities and compositional differences. Also, a soil humin, isolated in DMSO + H2SO4, was compared with a humin material isolated following the destruction of the clay to which it was sorbed. The inclusion of urea in the base system gives rise to the isolation of humic components that would be 'contaminants' in the soil humin materials. Its inclusion in the basic solvent will result of interactions with carbonyl functionalities in the organic substrates giving a slight increase in the N contents of the fractions isolated. Otherwise, the spectroscopic evidence indicates that the composition of the urea-amended isolate is the same as that of the equivalent base solution extract at pH 12-13. The compositions of the cellulose and lignin materials used were not altered by the base/urea solvent. The DMSO + H2SO4 solvent enabled a 'true' soil humin to be isolated and did not alter the compositions of the cellulose and lignin materials used. Exhaustive urea-amended base extractions of soil allow the isolation of humic and fulvic acids-free, unaltered soil humin when H2SO4-amended DMSO solvent is applied in sequence. These solvents do not give significant alterations to the compositions of the lignin and 'crystalline' cellulose, insoluble biomass components with significant contribution to the soil humin fraction obtained by ordinary methods (e.g., HF/HCl demineralisation). The same can be considered to apply for the cuticular materials, which have higher resistances to transformations.  aCellulose  aExtraction  aLignin  aUrea  aDMSO  aSoil humin1 aNOVOTNY, E. H.1 aHAYES, M. H. B.  tJournal of Soils and Sedimentsgv. 23, 1146-1155, 2023.