Electrochemical deposition of sol-gel films for enhanced chromium(VI) determination in aqueous solutions.

A pyridine-functionalized sol-gel film has been formed by electrodeposition at a glassy carbon electrode surface. When this protonated film is exposed to a Cr(VI) solution, the Cr(VI) anions are preconcentrated at the electrode surface. Using square wave voltammetry, the Cr(VI) species are reduced to Cr(III), and a peak current corresponding to this reduction is generated at 0.17V. The peak currents can be correlated with the Cr(VI) concentration. The functionalized sol-gel films demonstrated an enhanced sensitivity for Cr(VI) in aqueous solutions, providing a limit of detection at the low ppb level. Interference studies also displayed the high selectivity of the films for Cr(VI), and the system was able to tolerate a large excess of Cr(III) with no adverse affects. The reported electrodeposition method of film formation uses commercially available reagents and yields films quickly and reproducibly. The growth of these sol-gel films was monitored using an electrochemical quartz crystal microbalance (EQCM), and they were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The reported work shows the promise of such an electrode for use in Cr(VI) sensing applications.