Relationships between polarity, aliphaticity/aromaticity, fluorescence, and molecular size of soil ha electrophoretic fractions

Abstract

Reverse-phase ultra-performance liquid chromatography (RP-UPLC) with online absorbance and fluorescence detection was used for analysis of chernozem soil humic acids (HAs) and their fractions A, B, and C + D with different electrophoretic mobility (EM) and molecular size (MS). A strong relationship between fluorescence properties, EM, MS, polarity, and aliphaticity/aromaticity of HAs fractions was found. Humic and protein-like fluorescence had different polarity nature. Protein-like fluorescence is located in humic material which irreversibly adsorbed on the reversed-phase column and was not subjected to RP-UPLC characterization. The humic-like fluorescence is mostly located in the hydrophilic part of fraction C + D. Taking into account that high MS fraction A consists mainly of aliphatic components, it is reasonable to suggest that these associations are capable of organizing into micellar structures.