ELECTROCHEMICAL DETECTION OF HERBICIDES AND PLANT-GROWTH REGULATORS AT MEMBRANE GLASSY-CARBON ELECTRODES

Membrane glassy carbon electrodes modified with cation-exchangers (Eas tman AQ-29D, laponite, or polystrene sulfonate) entrapped between the membrane and the carbon surface were used to study the electrochemical behavior of herbicides and plant growth regulators from the quarterna ry ammonium family, Cations are shown to incorporate in the entrapped solutions containing negatively charged cation-exchangers, because of favorable electrostatic interactions. In the case of nonelectroactive cations, collection of mepiquat, chlormequat and difenzoquat from the bulk solution is assessed from the competition in ion-exchange equilib rium between one of the above-mentioned cations and the electroactive diquat cation. An attractive property results from the use of spinach ferredoxin as cation-exchanger inside the membrane electrode. Promotio n of ferrsedoxin is shown to be evidenced as a result of the collectio n of nonelectroactive cations from the bulk solution. Prospects of suc h modified membrane electrodes In the environmental field are discusse d.