Polarographic electrodes

Increased pressure [hyperbaric chamber, respiratory ventilators (eg, PEEP or CPPB)] P02 polarographic electrode "error" due to halogenated hydrocarbons (eg, llalothane) t P02 usually <50... 

Poa polarographic electrode "error" due to halogenated hydrocarbons (eg, Halothane)... 

Implementation Confirmation of the in situ monitors results is obtained when river water samples are brought to the lab and tested for dissolved oxygen using a lab dissolved oxygen probe (a polarographic electrode-based measurement) and the classic Winkler oxygen titration method. 

Mitochondrial function and potential dmg effects such as uncoupling and inhibition of OXPHOS are most directly studied by monitoring oxygen consumption or membrane potential, using polarographic electrodes and fluorescent dyes, respectively, but other techniques are available, as noted below. 

Second in popularity only to the pH electrode is the oxygen electrode. This device is a polarographic electrode system that can be used to measure oxygen concentration in a liquid sample or to monitor oxygen uptake or evolution by a chemical or biological system. 

Immobilized xanthine oxidase with a polarographic electrode (fish freshness) Pegasus Industrial Specialties Ltd., Canada... 

Dissolved oxygen polarographic electrode (InPro 6050, Mettler-Toledo, 2006) The cathode, where the half-reaction with 02 (02 + 2H20 + 4e —> 40H ) takes place, is in contact with a membrane, that allows the transport of the dissolved oxygen from the external medium. At the anode, the silver oxidation (Ag + Cl- —> AgCI + e ) takes place. 

The method is usually adopted when the transferring component is 02, since it is possible to monitor the dissolved oxygen concentration with a polarographic electrode(Clark cell). The method requires some precautions. The probe has an intrinsic time constant tp (the time needed to attain 63% of the reading after a stepwise concentration change) so that its output is not directly related to the actual concentration, especially when the concentration in the liquid phase changes rapidly. Indeed the measurement may be... 

In continuous reactors, for perfect mixing in each phase a measurement of the difference in concentration between outlet and inlet permits determination of kLaL. In practice, this method can be used for a reacting system when the liquid-phase concentration is maintained at a low value. Mukhopadhyay and Ghose (1976) employed this technique in large fermenters, where they measured gas-phase concentrations of oxygen at the inlet and outlet and the liquid-phase concentration in the fermenter using polarographic electrodes. 

FIGURE 4 O2 (upper) and force (lower) recordings from an a-toxin-permeabilized guinea pig ileum strip incubated in a closed chamber with a polarographic electrode (cf. Hellstrand and Paul, 1983). Solutions contain PCr (12 mM) and MgATP (3.2 mM). Pyruvate (10 mM) -I- malate (5 mM) added as indicated. Arbitary units. Numbers above O2 record show O2 consumption (background subtracted) relative to first period after addition of pyruvate -1- malate. 

Because these methods are so deeply rooted in the polarographic tradition and even now are frequently used with polarographic electrodes, we begin with a discussion of phenomena at dropping mercury electrodes and then develop the subject through conventional polarography and into various forms of pulse voltammetry. 

Fig. 7. Reduction of dissolved oxygen concentration in a suspension of Hydro-genomonas H16 stirred under an atmosphere of 10 per cent oxygen, 10 per cent carbon dioxide, and varying concentrations of hydrogea 4.5 g cells dry weight per liter gas flow rate 300ml/min temperature 30°C 700rpm. Oxygen was measured using a polarographic electrode...

Polarographic Electrodes. Polarographic electrodes usually contain a platinum or gold cathode, a silver/silver chloride anode, and a potassium chloride electrolyte. Figure 4.3a shows a schematic representation of a polarographic electrode. When the anode of the electrode is polarized by an external power supply, the following reactions take place at the surface of the electrode (Linek et al., 1985 Turner and White, 1999 van Dam-Mieras et al., 1992) ... 

Figure 4.4 Typical polarographic electrode polarogram. Adapted from Lee and Tsao (1979).

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