Assessing a Spectroelectrochemical Sensor’s Performance for Detecting [Ru(bpy) 3 ] 2+ in Natural and Treated Water

A spectroelectrochemical sensor that combines three modes of selectivity in a single device was evaluated in natural and treated water samples using tris‐(2,2′‐bipyridyl) ruthenium(II) dichloride hexahydrate, [Ru(bpy) 3 ] 2+ , as a model analyte. The sensor was an optically transparent indium tin oxide (ITO) electrode coated with a thin film of partially sulfonated polystyrene‐ block ‐poly(ethylene‐ ran ‐butylene)‐ block ‐polystyrene (SSEBS). As the potential of the ITO electrode was cycled from +0.7 to +1.3 V, the analyte changed from the colored [Ru(bpy) 3 ] 2+ complex to colorless [Ru(bpy) 3 ] 3+ complex and the change in absorbance at 450 nm was used as the optical signal for quantification. Calibration curves were obtained for [Ru(bpy) 3 ] 2+ in natural well water, river water and treated tap water with detection limits of 108, 139 and 264 nM, respectively. A standard addition method was developed to determine an ‘unknown’ spike addition concentration of [Ru(bpy) 3 ] 2+ in well water. The spectroelectrochemical sensor determined the concentration of [Ru(bpy) 3 ] 2+ spiked into a sample of Hanford well water to be 0.39±0.03 µM versus the actual concentration of 0.40 µM.