Development of Surface-Modified Microelectrode Arrays for the Electrochemical Detection of Dihydrogen Phosphate

Platinum and gold microelectrode arrays (MEAs), fabricated on silicon substrates with different geometric characteristics, were surface-modified by the potentiostatic electropolymerization of the pyrrole-ferrocene derivative Py(CH2)3NHCOFc, in the case of the platinum MEAs, and chemisorption of the thiol-functionalized ferrocene HS(CH2)6Nþ(CH3)2Fc, in the case of the gold MEAs. Cyclic voltammetry of these MEAs was typical of thin film behavior. The modified MEAs were investigated for the detection of the dihydrogen phosphate mono-anion in nonaqueous media via differential pulse voltammetry. This was based on electrostatic interaction and/or hydrogenbonding between the target anion and the amide-ferrocene or ammonium-ferrocene functionalized electrode surfaces. A decrease in the ferrocene (Fc) oxidation peak current with a concomitant increase in the peak current of a new peak at lower potentials was observed when the concentration of the dihydrogen phosphate was increased

Paper-Based System for Ion Transfer Across the Liquid-Liquid Interface

While ion transfer studies were shown to be a promising method for fundamental electrochemistry, pharmacokinetic studies, and sensing, they suffer from inherent instability of the interface formed between the organic and aqueous phases. This limits to some extent the range of solvents which can be used and confines these studies to the laboratory. We propose here the use of paper, which has revolutionized the way we think of miniaturized analytical devices during the past decade, as a perfect substrate for ion transfer studies across the liquid-liquid interface. We describe the design of a simple three-phase electrode paper-based setup for redox-driven transfer of anions from an aqueous to an organic phase. Electrochemical measurements of seven different anions and concentration dependence studies are in good agreement with the results obtained with traditional setups. Additionally, we show the applicability and limitations of such setups to the analysis of anion mixtures