Electroanalysis at Salt - Cotton - Electrode Interfaces: Preconcentration Effects Lead to Nano-Molar Hg2+ Sensitivity

Hydrogen peroxide detection in wet air with a Prussian Blue based solid salt bridged three electrode system

We report on a novel electroanalytical system for hydrogen peroxide (H2O2) detection in humidity or droplets of aerosol, formed by air bubbling through a washing chamber; the resulting flow mimics the exhaled human breath. The system is based on a planar three-electrode structure (with a Prussian Blue based H2O2 transducer modified working electrode) bridged by a solid salt-saturated filament material (filter paper, cotton textile). Respective to the hydrogen peroxide content in the washing valve, the response of the aerosol-sensing system is linear in the concentration range of 0.1-10 μM, which overlaps the generally accepted H2O2 content in exhaled breath condensate (EBC), with the sensitivity of 8 A M(-1) cm(-2). The response to the upper limit of the calibration range is stable for more than 50 injection cycles recorded within 3 days. Both the stability and the suitable calibration range allow one to consider the reported aerosol-sensing system as a prototype for a simple (avoiding intermediate EBC collection) noninvasive diagnostic tool for pulmonary patients.

Nano-TiO(2)-flavin adenine dinucleotide film redox processes in contact to humidified gas | salt electrolyte

Redox processes in nano-TiO(2)-flavin adenine dinucleotide (TiO(2)-FAD) layer-by-layer assembled films on ITO substrate electrodes are investigated and compared in contact to aqueous electrolyte media (for dilute and saturated electrolyte) and in contact to solid humidified salt electrolyte (for extreme salt levels and different types of salts). Under these unusual conditions an aqueous microphase present at the gas | salt | electrode interface allows voltammograms to be obtained and redox processes to be analysed. It is demonstrated that the 2-electron 2-proton reduction of FAD can be used as reporter redox system to determine local pH at the electrode | gas | salt interface as pH 15, 12, 7 for contacts to K(3)PO(4), K(2)HPO(4), and KH(2)PO(4), respectively. Exposure to gases such as carbon dioxide is shown to lead to unexpected changes in surface pH. In the future, bio-electrochemical microphase processes under halophilic conditions could be useful for air-quality and rapid gas sensing devices.