Electrochemical detection of nitrate at a copper modified electrode under the influence of ultrasound

Ultrasound has been applied to the detection of nitrate using a copper modified electrode. The electrode systems employs a macroporous copper deposit whose response to nitrate ion has been previously characterized. This report details the influence ultrasound (20 kHz) exerts on the structure of the deposit and on the response to nitrate. The deposit was substantially removed by the acoustic streaming and cavitational processes common to 20kHz ultrasound even at relatively mild power outputs and large horn electrode separations. However, bombardment with 20 kHz ultrasound does not remove the deposit entirely with a compact copper layer remaining. This portion of the deposit was found to retain significant nitrate sensitivity compared with the bare, unmodified electrode. The retention of the compact catalytic layer under the influence of ultrasound enabled the use of sonolinear sweep voltammetry which was found to provide signal enhancement significantly greater than the response observed under silent conditions. The analytical utility of the technique was assessed through the determination of nitrate in treated sewage outfall water. The silent and sonochemical results were found to be within 5% of the value obtained from an independent spectroscopic analysis.