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Keywords:

  • absorption spectrum;
  • gel filtration;
  • hydrophobic interaction;
  • PEON;
  • size exclusion

Abstract

To examine whether neutral phosphate buffer (NPB) extractable soil organic matter (SOM) is a homogeneous compound, we isolated NPB-extractable SOM using preparative size exclusion chromatography (PSEC) and analyzed them with high performance liquid chromatography using two different separation modes: size exclusion chromatography (SEC) and hydrophobic interaction chromatography (HIC). Fractions isolated using PSEC had different retention times in both SEC and HIC. Their apparent molecular weights based on SEC retention time and a protein standard ranged from 2,100 to 34,000 Da. These fractions also had a different adsorption ratio to a HIC column, which implies a difference in the hydrophobicity of the components between fractions. The magnitude of these differences varied among the four soil types investigated (Haplic Andosol, Low-humic Andosol, Cambisol and Gleysol). These results suggest that NPB-extractable SOM, rather than being uniform, is an assembly of compounds with diverse constituents and molecular weight distributions.