Utility of Nuclear Magnetic Resonance for Determining the Molecular Influence of Citric Acid and an Organosilicone Adjuvant on Glyphosate Activity

In the discipline of Weed Science, nuclear magnetic resonance (NMR) has been used extensively for obtaining structural information on herbicide compounds in the areas of herbicide synthesis, metabolism, and environmental degradation. However, little research has been published with regard to the utilization of NMR in determining molecular interactions in the spray solution. The molecular influence of citric add and an organosilicone adjuvant on glyphosate was analyzed with NMR spectrometry. 14 C-glyphosate absorption studies showed a decrease in glyphosate absorption by sunflower when Ca 2+ was added to the spray solution. This absorption antagonism was overcome with the inclusion of an organosilicone adjuvant. 1 H-NMR was used to stow that the organosilicone adjuvant did not directly interact with the glyphosate molecule nor did it prevent the formation of Ca-glyphosate. Citric add was effective in overcoming the Cat 2+ antagonism of glyphosate activity when the citric add concentration was 2× or 4× the Ca 2+ molar concentration based on plant fresh weight and plant height, respectively. 1 H-NMR was utilized to show that citric acid reacted with Ca 2+ in solution to produce Ca-citrate and prevent the formation of Ca-glyphosate. NMR was an effective technique for characterizing chemical interactions among the spray solution components.