Determination of MCPA through Electrocatalysis by Manganese Species

MnO2-modified carbon paste (CP) electrodes and Mn-modified glassy carbon (GC) electrodes show the electrochemistry of Mn species which strongly depends on the solution pH. Both types of modified electrodes are capable of catalytically reducing monochlrophenoxy acetic acid (MCPA), a herbicide. However, the catalytic wave appears at a lower potential at the MnO2-modified CP electrode than that at the Mn-modified GC electrode, thus enabling the modified CP electrode for the determination of MCPA. Amperometric determination of MCPA at the MnO2-modified CP electrode results in a very low detection limit of 0.20 ppm. The application of the proposed method for quantitative analysis of an MCPA formulation provides reliable results. Interaction of MCPA with MnO2 is observed even in the absence of applied potentials mimicking the real situation in the environment where MCPA, when introduced to farmland, would interact with MnO2 if present in soil.