Gold electrode potentiometric

For many systems the gold electrode is as satisfactory as the platinum electrode. Both rhodium and palladium as well as carbon have been used for specialized systems as inert potentiometric electrodes. 

Horrocks et al. (74) performed similar tip-substrate voltammetric experiments where the potentiometric pH tip response was recorded while scanning the potential of a substrate electrode. Significant pH variations in the vicinity of a gold electrode reducing oxygen were observed with antimony tips. 

Urease EC 3.5.1.5 adsorbed on a gold electrode nh Liquid membrane ISE, potentiometric 30... 

Triazenes ArN=NNHAr are formed as by-products of the diazotization reaction of primary aromatic amines. They can be determined by liberating the amine ArNH2 in strong acid, followed by potentiometric titration with nitrite in hydrobromic acid, using a gold electrode and a standard calomel electrode... 

The principle used is similar to that used for sensors made with tin dioxide or beta-alumina, the only differences being located at the level of the electrodes two gold electrodes for the tin dioxide used as a resistant sensor, a gold electrode and a platinum electrode for beta-alumina, used as a potentiometric sensor. 

Many conductometric titrations have been carried out in solutions of molten mercury(II) bromidei o. Por potentiometric work a gold electrode has been found to give nearly reproducible potential values i. It has been suggested that conductometric and potentiometric methods could be used for the estimation of certain electrolytes in molten mercury(II) bromidei i. For example mercury(II) oxide may be readily titrated with mercury(II) perchlorate in the bromide melt. 

It was also found that this approach based on use of composites has apparently contributed to sensor stability. For example, the use of nanocomposites of Au-MeO seems to resolve the instability of gold electrodes (Westphal et al. 2001). It was established that electrodes made from Au-Ga Oj, containing 20 wt% Ga Oj nanoparticles, in a potentiometric YSZ sensor, kept working and remained stable up to 850 °C. These Au-Ga Oj nanocomposite electrodes were prepared by using thick film technology and were sintered at between 900 and 950 °C. 

A five-electrode system was used with an SBDP with a gold electrode to measure potentiometric response correlated to local pH change through a porous membrane. The same SBDP fabrication method reported for redox probe diffusion was used, but electropolymerization of aniline to polyaniline (PANi) film on the Au portion of the probe enabled pH measurement. A porous polyimide membrane was mounted in... 

Numnuam et al. (2008) reported the first potentiometric aptasensor nsing ion-selective microelectrodes for THR detection. In the sandwich design, the THR was captured by a thiolated aptamer attached to the surface of the gold electrode and the measurements were based on cadmium sulfide quantum dot (CdS-QDs) label of the secondary aptamer. The potentiometric aptasensor presented good sensitivity allowing the detection of up to 28fmol of THR in PBS buffer solutions (detection limit of 0.14 nM). 

Although a few amperometric pH sensors are reported [32], most pH electrodes are potentiometric sensors. Among various potentiometric pH sensors, conventional glass pH electrodes are widely used and the pH value measured using a glass electrode is often considered as a gold standard in the development and calibration of other novel pH sensors in vivo and in vitro [33], Other pH electrodes, such as metal/metal oxide and ISFETs have received more and more attention in recent years due to their robustness, fast response, all-solid format and capability for miniaturization. Potentiometric microelectrodes for pH measurements will be the focus of this chapter. 

Metal/metal oxides are the materials of choice for construction of all-solid-state pH microelectrodes. A further understanding of pH sensing mechanisms for metal/metal oxide electrodes will have a significant impact on sensor development. This will help in understanding which factors control Nemstian responses and how to reduce interference of the potentiometric detection of pH by redox reactions at the metal-metal oxide interface. While glass pH electrodes will remain as a gold standard for many applications, all-solid-state pH sensors, especially those that are metal/metal oxide-based microelectrodes, will continue to make potentiometric in-vivo pH determination an attractive analytical method in the future. 

Potentiometric EDTA titrations are best carried out with a mercury pool electrode (Figure 5.6) or a gold amalgam electrode. When this electrode dips into a solution containing the analyte together with a small amount of added Hg-EDTA complex, three interdependent reactions occur. For example, at pH = 8 the half cell reaction (a) which determines the electrode potential is related to the solution equilibrium by (b) and (c). 

Redox-based biosensors. Noble metals (platinum and gold) and carbon electrodes may be functionalized by oxidation procedures leaving oxidized surfaces. In fact, the potentiometric response of solid electrodes is strongly determined by the surface state [147]. Various enzymes have been attached (whether physically or chemically) to these pretreated electrodes and the biocatalytic reaction that takes place at the sensor tip may create potential shifts proportional to the amount of reactant present. Some products of the enzyme reaction that may alter the redox state of the surface e.g. hydrogen peroxide and protons) are suspected to play a major role in the observed potential shifts [147]. 

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