title: Subnanomolar ion detection by stripping voltammetry with solid-supported thin polymeric membrane.
abstract: Subnanomolar limits of detection (LODs) are obtained for stripping voltammetry based on ion transfer at the interface between the aqueous sample and the thin polymeric membrane supported with a solid electrode. It has been predicted theoretically that a lower LOD can be obtained for a more lipophilic analyte ion, which can be preconcentrated at a higher equilibrium concentration in the solid-supported thin polymeric membrane to enhance a stripping current response. This study is the first to experimentally confirm the general theoretical prediction for both cationic and anionic analytes. Proof-of-concept experiments demonstrate that a subnanomolar LOD of (8 +/- 4) x 10(-11) M tetrapropylammonium is significantly lower than a LOD of less lipophilic tetraethylammonium. Importantly, stripping voltammetry of the cationic analytes is enabled by newly introducing an oxidatively doped poly(3,4-ethylenedioxythiophene) film as the intermediate layer between a plasticized poly(vinyl chloride) membrane and a Au electrode. On the other hand, an undoped poly(3-octylthiophene) film is used as an intermediate layer for voltammetric detection of a lipophilic inorganic anion, hexafluoroarsenate, an arsenical biocide found recently in wastewater. A LOD of (9 +/- 2) x 10(-11) M hexafluoroarsenate thus obtained by ion-transfer stripping voltammetry is comparable to a LOD of 80 pM by inductively coupled plasma mass spectrometry with anion-exchange chromatography. Great sensitivity for a lipophilic ion is potentially useful for environmental analysis because high lipophilicity of an ion is relevant to its bioaccumulation and toxicity.
authors: Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, USA.
authors: Yushin
authors: Y
authors: Kim
authors: Patrick J
authors: PJ
authors: Rodgers
authors: Ryoichi
authors: R
authors: Ishimatsu
authors: Shigeru
authors: S
authors: Amemiya
mesh_terms: D001149:Arsenates / Q000032:analysis*; D004563:Electrochemistry / Q000379:methods*; D017736:Ion-Selective Electrodes; D008567:Membranes, Artificial; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D012680:Sensitivity and Specificity; D019789:Tetraethylammonium / Q000032:analysis*
chemical_list: D001149:Arsenates; D008567:Membranes, Artificial; D000644:Quaternary Ammonium Compounds; C052377:tetrapropylammonium; D019789:Tetraethylammonium