Design and fabrication of a microelectrode array for iodate quantification in small sample volumes

A method for the simple manufacture of microelectrode arrays is described. The construction technique is based on microelectronics technology by conventional sputtering deposition of layers of Ni/Cr and Au, photolithography and a final treatment to improve the chemical stability of the device. Cyclic voltammetry at both sulphuric acid and ferricyanide solutions was employed to inspect the operation of the microelectrodes, which can be individually addressable. This microelectrode system has been used successfully for indirect amperometric measurements of the iodate content in very small volumes (typically 50–200 μL) of solutions prepared from the dissolution of commercial Brazilian salt samples, which illustrates its potentiality as useful tools in electroanalytical chemistry. The possibility of modifying the surface of the gold microelectrodes by electrodeposition of molybdenum oxides was also investigated. The results indicated that the device can also be used as a practical sensor for measuring directly iodate owing to the enhancement of the reduction signal by an electrocatalytic process.