LASER ELECTROCHEMICAL DETECTION TECHNIQUE IN A FLOW SYSTEM

A platinum electrode was illuminated with an intermittent Ar+ laser beam in a flowing solution from the front side of the electrode. The current induced by this laser illumination was recorded as a function of electrode potential with a lock-in amplifier and was directly observed with an oscilloscope. Experimental results for the [Fe(CN)6]4-, [Fe(CN)6]3-, Fe2+ and Fe3+ solutions indicated that the laser heating of the electrode promotes or depresses the electron transfer process, depending on the standard entropy change of the electrode reaction, promotes the mass transfer process and induces adsorption or desorption of anions. Further, the induced current was proportional to the concentration and strongly depended on the chopping frequency and the flow rate. This laser electrochemical (LEC) detection can be used as a new electrochemical detector in electroanalytical chemistry.