Electrochemical monitoring of the oxidative degradation of glyphosate with UV/H2O2

Abstract

A voltammetric method optimized for the sensitive and reliable study of the UV/H2O2 oxidation of glyphosate (N- (phosphonomethyl) glycine) (GPS). The cell consisted of three electrodes in a compartment, silver wire coated with silver chloride as a pseudo reference electrode, platinum electrode as working electrode and stainless steel as auxiliary electrode. GPS cyclic voltammetric analysis suggests the formation of a GPS-Pt complex on the electrode surface, with an enhanced signal in perchloric acid between 1.3 to -1.3V; sensitive to protonation of the amino group, no response observed at pH values greater than 5.00. The oxidative degradation of GPS with UV/H2O2 is evident at pH 3.0, it exhibits first order pseudo kinetics with a half-life of 40 ± 4min. Two degradative routes are estimated depending on the concentration of H2O2: at low concentrations (H2O2/GPS 1: 100 ratio), the formation of sarcosine and then glycine is favored; at H2O2/GPS 1:20 and 1:10 ratios predominate the formation of glycine.