INFRARED AND FLUORESCENCE SPECTROSCOPY OF GLYPHOSATE-HUMIC ACID COMPLEXES

The herbicide glyphosate is increasingly used for its low toxicity and high rate of degradation in soils. Glyphosate is known to interact in soils with iron and aluminum oxides and to form insoluble complexes, whereas limited attention has been devoted to the study of chemical interactions of glyphosate with soil organic components. The objective of this investigation was to evaluate the possible occurrence of glyphosate-humic acids complexes. Samples were freeze-dried and analyzed by infrared and fluorescence spectroscopy in the emission, excitation and synchronous-scan excitation modes. Spectroscopic results showed an apparent disaggregation of the humic molecule with increasing glyphosate content, probably due to an increasing extent of hydrogen bonding interactions between the phosphono groups of glyphosate and the humic polymer.