Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 3. Effect of signal averaging on limit ofdetection

The effect of ensemble averaging on the response of a new spectroelectroche mical sensor has been investigated. The sensor consists of a selective him coated over an optically transparent electrode (OTE), The mode of detection is attenuated total reflection (ATR), For an analyte to be detected, it mu st first partition into the sensing film, second be electroactive at the ap plied potential, and third have a change in its absorbance at the wavelengt h of light monitored by ATR. Four different excitation potential waveforms were investigated: pulsed, step, triangular, and sinusoidal. Under the cond ition of continuous cycling of the excitation potential, the optical respon se approaches a steady-state condition within as few as five cycles. Once t he response has reached steady state, ensemble averaging over successive cy cles is shown to improve the signal-to-noise ratio, allowing an order of ma gnitude improvement in the limit of detection. A model sensor consisting of a cationically selective sol-gel-derived Nafion composite film coated on a n indium tin oxide OTE is employed to demonstrate the signal acquisition te chniques under investigation. Tris(2,2'-bipyridyl)ruthenium(II) chloride wa s used as a model analyte.