Simultaneous Detection of Two Analytes Using a Spectroelectrochemical Sensor

摘要

Spectroelectrochemical sensors developed in our groupnachieve three modes of selectivity by combining electrochemistry,nspectroscopy, and a chemically selective membranenin a single device. Analyte detection is based uponna change in the optical response due to the conversion ofnthe analyte between two oxidation states that results fromnthe cycling or stepping of the applied potential. We havendemonstrated a novel approach to simultaneously detectntwo metals by combining optical stripping voltammetry fornone metal (Pb2+) and the in situ ligand complexationnin a film for the other metal (Fe2+). Using an indiumntin oxide (ITO) sensor platform with a 50 nm Nafionnfilm to preconcentrate the analytes, equimolar mixturesnof Pb2+ and Fe2+ in 0.1 M sodium acetate buffern(pH 5) were detected. Pb2+ was detected by opticalnstripping voltammetry, in which lead was deposited asnmetal on the ITO and detected by the optical changenas it was removed by stripping. The ferrous ion wasndetected by the in situ ligand complexation method innwhich Fe2+ was complexed with 2,2′-bipyridyl in thenNafion in the film to form an intense red complex thatnwas detected by absorbance at 520 nm. Detectionnlimits of 300 and 400 nM were obtained for Pb2+ andnFe2+, respectively. The presence of the film had noneffect on the optical signal that results from the depositionnand stripping of the Pb2+. In addition, competitionnbetween the Pb2+ and Fe2+ for sites in the film and fornthe organic ligand was investigated.