Potentiometric gas sensing electrodes

Abstract

A num her ofpotentiometric gas sensing electrodes using a hydrogen or other ion sensing electrode and agaspermeable mem brane have been st udied. A theoretical model has been developed describing the time response, electrical potential behaviour and Iimit of detection as a function of membrane properties, geometry, and internal electrolyte composition. Electrodes responding to carbon dioxidc, ammonia, amines, sulphur dioxide, nitrogen dioxidc, hydrogen sulphidc, hydrogen cyanide, hydrogen fluoride, acetic acid, and chlorine have been constructed and their response characteristics are found to be in good agrecment with thc theorctical predictions.

Determination of Free Sulfur Dioxide in Wine by Using a Biosensor Based on a Glass Electrode

“…Some biosensors 6 10) based on the glass electrode have been developed for sugar, urea and penicillin, but have not yet been reported for sulfur dioxide determination. While a sulfur dioxide electrode 11) was developed earlier, the electrode was not specific to sulfur dioxide, and the internal solution of the electrode was unstable during measurement.…”

The development of pH and pCO2 microelectrodes for studying the carbonate chemistry of pore waters near the sediment‐water interface

“…In principle, the rate of the electrode response depends on partitioning and diffusion of CO2 into the silicone membrane, hydration of CO2 in the NaHCO, layer, and diffusion and species intcrconversions as C02, HC03-, and C032-come to equilibrium in the NaHC03 layer. The partitioning of CO2 between solution and the hydrophobic membrane is usually instantaneous (Ross et al 1973). When the [CO,] of the sample solution changes from Ci to C,, the outer surface of the membrane will change instantly from C, to C,, while the internal surface will change from C, to C2 gradually.…”

“…This delay can be expressed in terms of the sensor's response time, t (Ross et al 1973 CO,-permeable hydrophobic membrane; c = EC2 -c2) 1 C, -C 1 /C, -the fractional approach to equilibrium; C-CO2 concentration in the Na The terms are defined as follows: I-thickness HC03 thin layer; at t = 0, C = C, , when 100% of the NaHCO, thin layer; m -thickness of the response is reached, or c approaches zero, C = C2; dC,/dC-changes of total carbon as a function of [CO,] change in the NaHCO, layer; D-diffusion coefficient of CO2 in the hydrophobic membrane phase; K-partitioning coefficient of CO2 between the aqueous solution and the membrane material, K = C/C,,; Cm-CO2 concentration in the hydrophobic mcmbrane; &-total C.…”

“…It was assumed to be close to one and constant in the model of Ross et al (1973). As Jensen and Rechnitz (1979) pointed out, dCT/ dC can exceed 1 if [CO,] is low (<O.…”

Chemically modified electrodes: Recommended terminology and definitions (IUPAC Recommendations 1997)

“…While CMEs can operate both amperometrically (or voltammetrically) and potentiometrically, they are generally used amperometrically, a faradaic (charge transfer) reaction being the basis of experimental measurement or study, whereas ISEs are generally used in potentiometric formats where a phase-boundary potential (interfacial potential difference) is the measured quantity [2]. Gas-sensing electrodes (e.g., for C02, NH3, NOx) are also potentiometrically based [3] although the oxygen electrode, which functions amperometrically, is an exception [4]. Chemically sensitive field effect transistors (CHEMFETs) are basically non-faradaic electrode systems in which electric field variations in the semiconductor gate region control the magnitude of the source-drain current [5].…”