Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device. 3. Effect of Signal Averaging on Limit of Detection

The effect of ensemble averaging on the response of a new spectroelectrochemical sensor has been investigated. The sensor consists of a selective film coated over an optically transparent electrode (OTE). The mode of detection is attenuated total reflection (ATR). For an analyte to be detected, it must first partition into the sensing film, second be electroactive at the applied potential, and third have a change in its absorbance at the wavelength of light monitored by ATR. Four different excitation potential waveforms were investigated: pulsed, step, triangular, and sinusoidal. Under the condition of continuous cycling of the excitation potential, the optical response approaches a steady-state condition within as few as five cycles. Once the response has reached steady state, ensemble averaging over successive cycles is shown to improve the signal-to-noise ratio, allowing an order of magnitude improvement in the limit of detection. A model sensor consisting of a cationically selective sol−gel-derived Nafion composite film coated on an indium tin oxide OTE is employed to demonstrate the signal acquisition techniques under investigation. Tris(2,2‘-bipyridyl)ruthenium(II) chloride was used as a model analyte.