Electrodes continued reference

Fig. 16. Small-scalo laboratory cell for preparative electrolysis. A, Pt gauze working electrode. B, Pt sheet secondary electrode. C, Reference electrode. D, Luggin capillary on a syringe barrel so that the position of the tip of the Luggin probe relative to the working electrode is readily adjustable. E, Glass sinter to separate anode and cathode compartments. F, Gas inlet to allow stirring with inert gas or the continuous introduction of reactant. G, Three-way tap where a boundary between the reference electrode and the working solutions may be formed.

Potentiometry with ISEs is the electroanalytical technique most frequently used with continuous segmented configurations. Figure 5.15 shows an assembly designed for the simultaneous determination of sodium and potassium In animal urine [33], The system Is in fact composed of two distinct units for the determination of each analyte. The sample is aspirated and split prior to the peristaltic pump into two channels, which are subsequently mixed with an appropriate buffer (Tris/acetlc acid of pH 8.15 for sodium and diethylamine/acetlc acid for potassium) and de-aerated before they reached their respective selective electrodes. The reference electrode Is an ordinary one and Is connected to both streams, Into which are Introduced two platinum wires connected to the... 

A microvial with electrodes in the wall is used in this method. The volume of fluids can be calculated by exhaustive reduction of current under the effect of continuous changed voltage (Fig. 3). Recessed microdisk (RMD) electrode, tubular nanoband (TNB) electrode and reference electrodes were installed on the bottom, sidewall and... 

Electrochemical reduction was conducted in a three compartment cell, at constant potentials corresponding to the E1/2 of the first one-electron wave for each compound. The cathode was a mercury pool (area 12 cm ) stirred magnetically with a teflon-coated bar, with a saturated calomel electrode as reference electrode. The cell was continuously flushed with argon during electrolysis. Model OH-404 C integrator (Radelkis, Hungary) was used to determine the number of electrons involved in the reduction process. 

TABLE 8.20 Potentials of Reference Electrodes in Volts as a Function of Temperature Continued)... 

Each of these two procedures can be varied by proceeding from a low to a high current density (or potential) or from a high to a low current density (or potential) the former is referred to as forward polarisation and the latter as reverse polarisation. Furthermore, there are a number of variations of the potentiostatic technique, and in the potentiokinetic method the pwtential of the electrode is made to vary continuously at a predetermined rate, the current being monitored on a recorder in the pulse method the electrode is given a pulse of potential and the current transient is determined by means of an oscilloscope. 

Prepare an approximately 0.1 M silver nitrate solution. Place 0.1169 g of dry sodium chloride in the beaker, add 100 mL of water, and stir until dissolved. Use a silver wire electrode (or a silver-plated platinum wire), and a silver-silver chloride or a saturated calomel reference electrode separated from the solution by a potassium nitrate-agar bridge (see below). Titrate the sodium chloride solution with the silver nitrate solution following the general procedure described in Experiment 1 it is important to have efficient stirring and to wait long enough after each addition of titrant for the e.m.f. to become steady. Continue the titration 5 mL beyond the end point. Determine the end point and thence the molarity of the silver nitrate solution. 

Potentiostatic conditions are realized with electronic potentiostats. The potential of the working electrode is monitored continuously with the aid of a reference electrode. When the potential departs from a set value, the potentiostat will adjust the current flow in the cell automatically so as to restore the original value of potential. Important characteristics of potentiostats are their rise time and the maximum currents which they can deliver to the cell. Modem high-quality potentiostats have rise times of 10 to 10 s. 

Catheter-type ion selective electrodes have been developed for continuous in vivo monitoring of ion activities and blood gases A miniature ion selective and reference... 

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