Highly Selective Potassium Ion Responsive Liquid-Membrane Electrode

Abstract

The performance of a new liquid-membrane electrode using valinomycin as membrane component is described with respect to selectivity, working range, speed of response and accuracy. The electrode makes possible the measurement of potassium ion activities in the range of 10^?1 M to at least 10^?6 M in unbuffered systems with a selectivity of potassium over sodium ions of more than 4,000. The electrode was used for the direct titration of potassium ions.     

Amino Acid-Responsive Liquid Membrane Electrodes

Abstract

Amino acid responsive electrodes based on the use of their quaternary ammonium salts in a liquid membrane phase have been prepared for tryptophane, phenylalanine, leucine, methionine, valine, and glutamic acid.     

Electromotive behaviour of anion selective membranes with triorganotin acetates as ionophores and nucleophiles as additives

The electromotive behaviour of neutral carrier based Cl^–-selective electrodes can be improved if lipophilic nucleophiles are added to the membrane phase containing triorganotin acetates as anion carriers. The addition of about 50 mol-% octadecanethiol to diethyl-n-hexyltin acetate as ionophore leads to improved sensor response times and to slopes of the electrode response function close to the Nernstian behaviour.     

Water transfer in mixed water-in-oil emulsions studied by differential scanning calorimetry

Water transfers are observed within complex systems containing aqueous phases separated by a membrane or an oil phase, such as biological cells or multiple emulsions. In order to better understand water transfer mechanism, a system made of a mixed water-in-oil (W/O) emulsion containing two kinds of aqueous droplets — pure water and a 30 % urea solution — was developed. Water transfer from pure water droplets to urea solution droplets was evidenced by Differential Scanning Calorimetry (DSC). Finally the mixed emulsion contains one kind of droplets made of a diluted urea solution which composition is in agreement with formulation and data obtained from experiments performed on single W/O emusions which dispersed phase is a diluted urea solution of the same composition. These mixed emulsions have been pictured as a three-fluid phases system containing two aqueous phases separated by a plane oil membrane. From a homogeneous solubility-diffusion model applied to a quasi-stationnary regime, the water intra-diffusion coefficient has been obtained and compared to the value calculated from the Stokes-Einstein equation. A factor ten makes the discrepancy between the two values, the value deduced from the model being the highest. A possible influence of the emulsifier molecules has been evoked.