Polarographic probes, oxygen

In air with a normal composition, the oxygen partial pressure is 0.21 atm, the O2 solubility would become 2.56 x 10 mol dm. The solubility of oxygen in water has been the subject of much literature. Currently the oxygen polarographic probe is usually used to measure solubility of O2 in aqueous solutions. ... 

Similar to the polarographic probe, the galvanic probe is constrained by the rate-limiting step of oxygen diffusion across the probe membrane. Thus, the current output of the probe is linearly related to the dissolved oxygen concentration in the bulk fluid. 

The mechanical properties of films were determined on an Instron Model 4500 using ASTM methods 1708 and 1938. Oxygen permeability (Dk) was determined using the polarographic probe method (72). 

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. 

On-site, dissolved oxygen is commonly measured using a membrane electrode of the polarographic type in a flow-through cell. The zero is commonly set using a saturated solution of sodium sulphite and the 100% saturated environment by holding the probe close to the surface of clean water. Below 1 ppm, electrodes provide only a qualitative measure of D02 due to slow electrode response (Wilkin et al., 2001). 

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 the pioneer work of Updike and Hicks (40), the enzyme glucose oxidase (GOD) was maintained in a layer of acrylamide gel over a polarographic oxy n electrode (actually the Clark oxygen electrode). The current output of this probe results from the reduction of oxygen at a platinum electrode and thus is a function of the oxj n tension. When oxygen is not rate limiting and the glucose concentration is below the apparent for the immobilized GOD, there... 

Wong RK, Fyles A, Milosevic M, Pintilie M, Hill RP (1997) Heterogeneity of polarographic oxygen tension measurements in cervix cancer an evaluation of within and between tumor variability, probe position, and track depth. Int J Radiat Oncol Biol Phys 39 405 412... 

Independent of the brand of polarographic oxygen sensor, a general calibration procedure has to be followed. The geometry and the membrane of the sensor define, within limits, the diffusion layers and consequently the temperature dependence of the oxygen probe. 

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