University of California Water Resources Center

Perchlorate (ClO4 -) contamination of ground water is a widespread problem in the U.S., which can adversely affect human health and wildlife. Current methods for detecting and quantifying ClO4 - in water are time consuming, expensive, and subject to error due to complex procedures and various interferences. Thus, there is an urgent need to develop a method that can accurately detect and measure low concentrations of ClO4 - in the field. This study reports the construction of a ClO4 -- reductase based biosensor for rapid determination of ClO4 - in water. Using a 3 mm GCE (glass carbon electrode), we successfully constructed a ClO4 - sensing bio-electrode by coating an aliquot of the enzyme on nafion (ion-exchange matrix) layer pre-coated on the polished surface of the GCE. Amperometric [i/t] measurements revealed linear increases in current in relation to time and ClO4 - concentration. The biosensor responded strongly to ClO4 - at concentrations as low as 1 μg/L and the sensor displayed a linear response to ClO4 - concentrations in the range 25 to 100 μg/L. Linear response time to ClO4 - at 100 μg/L was approximately111±28 seconds. Kinetic evaluation of the sensor response to ClO4 - revealed linear increases (r2 > 99%) in 10 min with k values of 10.3, 24.2, 33.9 and 48.2 at 25, 50, 75 and 100 μg/L, respectively. A strong linear correlation was established between biosensor response (nA) and ion-chromatography conductivity readings (μS) in the 25 to 100 μg/L linear domain of the biosensor. Biosensor response to ClO4 - was maximal at applied potential range of –0.6 to –1.0V. ClO4 - reduction current increased with an increase in pH and was maximal in the range of 7.6 to 8.0. The ClO4 - biosensor was significantly stable after repeated use (24 analyses conducted on day 1 over a 10-h period at room temperature). This study indicates great potential for the development of a portable biosensor for real time analysis of ClO4 - in water in the field.