Measured oxygen concentration

For trace quantities of less than 100 ppm, the most successful method — and the most costly— is neutron activation. The sample is subjected to neutron bombardment in an accelerator where oxygen 16 is converted to unstable nitrogen 16 having a half-life of seven seconds. This is accompanied by emission of (J and 7 rays which are detected and measured. Oxygen concentrations as low as 10 ppm can be detected. At such levels, the problem is to find an acceptable blank sample. 

As shown below, the influence of three quite distinct dynamic processes play a role in the overall measured oxygen concentration response curve. These are the processes of the dilution of nitrogen gas with air, the gas-liquid transfer, and the electrode response characteristic, respectively. Whether all of these processes need to be taken into account when calculating KLa can be seen by examining the mathematical model and making simulations. 

Measured oxygen concentration response curve 534 Measurement... 

Electrochemical cells where ions dissipate through a solid electrolyte are mainly used for measuring oxygen concentrations. The most common sensors based on this principle are the A-probe for monitoring combustion engines in motor vehi-... 

Supernatant BOD5 was measured by the standard method of the American Public Health Association (24), but using the EIL dissolved oxygen probe model no. 8012 to measure oxygen concentration (Electronic Instruments Ltd., Richmond, Surrey, UK.)... 

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. 

In the above-described set-up (Fig. 8.16), the physical absorption of oxygen in water was used to measure the gas to liquid mass transfer. Thin-film fluorescence quenching-based sensors were installed to determine the oxygen concentration at the inlet and exit of the reactor. From the measured oxygen concentrations, the mass transfer coefficient was calculated based on the reactor-based liquid velocity ... 

Enzyme electrodes play a vital role in the operation of - biosensor and -> biofuel cells. The term enzyme electrode was coined by Clark and Lyons after their first demonstration of a -> glucose sensor in which glucose oxidase was entrapped at a - Clark oxygen electrode using a dialysis membrane. The decrease in measured oxygen concentration was proportional to the glucose concentration. 

Measured oxygen concentrations in ocean surface waters as a function of temperature from the WOCE data base. The line marks the saturation value with atmospheric oxygen at a salinity of 35. 

The H2O2 feed rate is divided by 2 because of the stoichiometry of oxygen formation. As liquid temperature and salinity change during a measurement, oxygen concentrations in the liquid must be corrected accordingly. In addition, use of this method requires the following assumptions ... 

Proton resolution of CTPO is unusually good, with best resolution near 10°C, where the accidental degeneracy is nearly perfect. This resolution is lost when oxygen is present in the system, and the effect has been used by Lai et al. [40] to measure oxygen concentration. This technique is called spin-label oximetry . Lai s extensive calibration charts will be found useful for readers interested in this method. 

Heisenberg exchange between spin-labels and fast relaxing paramagnetic species including dissolved molecular oxygen or transition metals provides a thermal contact with the lattice and is an effective T, mechanism [43]. The effect has been used to measure oxygen concentrations [44]. 

MEASURING OXYGEN CONCENTRATION IN LEAD-BISMUTH HEAT CARRIERS... 

A good fit of the measured oxygen concentrations by a curve calculated from the eddy diffusion-advection model has been obtained by... 

There are a few common methods of measuring oxygen concentration in the gas phase. Electrochemical sensors and paramagnetic sensors are typically used to measure oxygen concentration on a wet and dry basis, respectively. Carbon monoxide (CO) is most commonly measured using a nondispersive infrared technique. A gas sample flows between an infrared radiation source and an infrared detector. Carbon monoxide absorbs infrared radiation, hence the difference in intensity proportional to the concentration of CO in the gas sample. 

In situ oxygen analyzer. The oxygen analyzer in this unit is not actually located in the stack. However, the sensing element is very close to the sample location to minimize lag time. Flue gases are rapidly educted across an electrochemical sensor that measures oxygen concentration in real time. 

The probe used is an in-situ type stabilized zirconia oxygen analyzer. The zirconium oxide cell is able to measure oxygen concentrations in hot, dirty gases without sample conditioning. In addition, the moisture content of the gas has no effect on the analyzer. 

The most successful SECSs are those which use zirconia-based electrolytes to measure oxygen concentrations. The three most common applications of these electrolytes are to measure oxygen concentrations of steel melts and in combustion gas environments and to control the air-fuel ratio in automobile engines. In the latter two applications, there is increasing interest in lowering the sensor temperature below 600°C, the current minimum temperature of operation because of low ionic conductivity and slow charge-transfer reactions at electrode-electrolyte interfaces. 

FIG. 6.12. Electrochemical meter for measuring oxygen concentration in sodium... 

Recently Catros et al. [89] measured oxygen concentration profiles in a 17.2 cm plexiglass column and a bed containing 0.508 mm particles. It was observed that axial dispersion was limited... 

Wilson DF, Rumsey WL, Green TJ, Vanderkooi JM. The oxygen dependence of mitochondrial oxidative phosphorylation measured by a new optical method for measuring oxygen concentration. J Biol Chem 1988 263 2712-2718. 

The CE, the amount of consumed alumina and the amount of produced aluminum, can be calculated during electrolysis based on the measured oxygen concentrations generated on the anode. 

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