Membranes amperometry

Flow injection analysis (FIA) (Ruzicka and Hansen), since 1975 In continuous flow, stopped flow or with merging zones (FIA scanning or intermittent pumping) Adapted voltammetric electrodes Membranes for Partial dialysis Membrane amperometry (Clark) Differential techniques (Donnan) Computerization, including microprocessors Special measuring requirements in plant control (to avoid voltage leakage, etc., Section 5.5)... 

Membranes. Apart from the role of membranes180 in ISEs, there are at least three important applications of membranes as measurement aids in flow analysis. viz., as diffusion membranes in (1) (partial) dialysis and in (2a) membrane amperometry (MEAM) and (2b) membrane voltammetry (MEVA), and as Donnan membranes in (3) differential ionic chromatography. 

One important application of amperometry is in the construction of chemical sensors. One of the first amperometric sensors to be developed was for dissolved O2 in blood, which was developed in 1956 by L. C. Clark. The design of the amperometric sensor is shown in Figure 11.38 and is similar to potentiometric membrane electrodes. A gas-permeable membrane is stretched across the end of the sensor and is separated from the working and counter electrodes by a thin solution of KCl. The working electrode is a Pt disk cathode, and an Ag ring anode is the... 

Hypochlorous acid can be distinguished from other chlorine species by amperometry using a membrane electrode (135). Spectrophotometry can also be used to measure HOCl via its absorbance maximum at 235 nm. Gaseous mixtures of CI2, CI2O, HOCl can be analyzed by mass spectrometry. 

In measurements of conductivity, no electrochemical reactions occur. Differences in conductivity are due to differences in the ionic strengths of solutions. An alternating potential is applied to the solution at a known potential. The current is measured and the conductivity in Siemens/cm calculated.16 In potentiometry, the analyte is presumed to undergo no electrochemical reaction. The potential at the electrode changes due to changes in potential across the surface of the membrane in a membrane electrode or at the electrode surface of a solid electrode. The most familiar example of a potentiometric electrode is the pH electrode. In amperometry, current does flow, due to reduction or oxidation of the substance being analyzed. 

We wish only to remind readers that there are three main methods of electrochemical re-vealment conductivity, direct current (d.c.) amperometry, and integrated amperometry (pulsed amperometry is a form of integrated amperometry). In revealment by conductivity, the analytes, in ionic form, move under the effect of an electric field created inside the cell. The conductivity of the solution is proportional to the mobility of the ions in solution. Since the mobile phase is itself an electrolytical solution, in order to increase the signal/noise ratio and the response of the detector, it is very useful to have access to an ion suppressor before the revealment cell. By means of ionic exchange membranes, the suppressor replaces the counterions respectively with H+ or OH , allowing only an aqueous solution of the analytes under analysis to flow into the detector. 

Physical entrapment between membranes Physical entrapment Amperometry 39, 93, 94... 

Sequential injection has proven itself especially useful for a variety of separation and preconcentration schemes, It has been applied to analvtical procedures involving such methods as membrane separations, pi I adjusinienLs. solid-phase e.xiraction. precipitation, and titration. In addition to colorimetry, ion-selective elecirodes. amperometry. Huoresccncc, IR abs >rplion. chemiluminescence, and conductimeiry have been used as detection methods wi(h SlA. 

Kunnecke and Schmid [40] introduced a gas-diffusion separation system combined with an immobilized alcohol oxidase column used for the determination of ethanol in beverages by amperometry. Ethanol vapour from the samples diffused through a silicone-modified polypropylene membrane and was collected in a potassium phosphate buffer acceptor stream before passing through the immobilized enzyme column where the ethanol was transformed into hydrogen peroxide. The peroxide was determined using an amperometric detector with excellent precision (cf. Sec. 8.4). 

Rain, fog, snow Direct measurement Amperometry 0.08-0.8 mgr Membrane-based separation... 

Different miniaturized flow injection analyzers have been constructed using spectrophotometry as a leading detection technique. Besides, electrochemical techniques such as amperometry and potentiometry with chemically modified solidstate electrodes and tubular membrane-based ISEs, respectively, have been proved to be well adapted to multiparametric measurements of inorganic species present in wastewater, using multiple sensor arrays. 

See also. Amperometry. Conductimetry and Oscillometry. Coulometry. Electrogravimetry. Ion-Selective Electrodes Oven/iew Glass Solid-State Liquid Membrane Gas Sensing Probes Water Applications. pH. Polarography Overview. Process Analysis Sensors. Sensors Overview Amperometric Oxygen Sensors. Sulfur. Voltammetry Overview Anodic Stripping. Water Analysis Industrial Effluents. 

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