Oxygen measurements

FIG. 24-14 Dissolved-oxygen electrodes a) polarographic (impress breakdown voltage for oxygen measure current) (h) voltametric (measure electromotive force). 

The reactivity of a series of hydrocarbons toward oxygen measured under a standard set of conditions can give some indication of the susceptibility of various structural units to autoxidation. Table 12.10 gives the results for a series of hydrocarbons. These data indicate the activating effect of alkyl, vinyl, and phenyl substituents. 

Calvet microcalorimeters are particularly convenient for such studies. Figure 19 show s, for instance, the evolution of the differential heat of adsorption of oxygen, measured at 30°C with a Calvet calorimeter, as a function of the total amount of oxygen adsorbed on the surface of a sample (100 mg) of nickel oxide, NiO(200) (19, 73). The volume of the first... 

The experimental set-up for cellular oxygen measurements (p02) consists of following components p02 measuring micro chamber (volume 0.6 microliter), polarographic microelectrode, water-bath for constant temperature, chemical microsensor connected to a strip-chart recorder and gas calibration unit. 

Wolfbeis O.S., Leiner M.J.P., Posch H.E., A new sensing material for optical oxygen measurement, Mikrochim. Acta (Vienna) 1986 HI 359. 

Optical sensors for oxygen measurement are attractive since they can be fast, do not consume oxygen and are not easily poisoned. The most common method adopted in construction is based on quenching of fluorescence from appropriate chemical species. The variation in fluorescence signal (I), or fluorescence decay time (x) with oxygen concentration [O2] is described by Stem-Volmer equation91 ... 

The first enzyme biosensor was a glucose sensor reported by Clark in 1962 [194], This biosensor measured the product of glucose oxidation by GOD using an electrode which was a remarkable achievement even though the enzyme was not immobilized on the electrode. Updark and Hicks have developed an improved enzyme sensor using enzyme immobilization [194], The sensor combined the membrane-immobilized GOD with an oxygen electrode, and oxygen measurements were carried out before and after the enzyme reaction. Their report showed the importance of biomaterial immobilization to enhance the stability of a biosensor. 

The lead content of biological samples is usually very small, rendering gravimetric methods impracticable, and methods have often relied upon the formation of coloured complexes with a variety of dyes. More recently, the development of absorption spectroscopy using vaporized samples has provided a sensitive quantitative method. Oxygen measurements using specific electrodes offer a level of sensitivity which is unobtainable using volumetric gas analysis. 

X.-M. Li, F.-C. Ruan, and K.-Y. Wong, Optical characteristics of a ruthenium(II) complex immobilized in a silicone rubber film for oxygen measurement, Analyst 118, 289-292 (1993). 

Figure 9.15 presents an example of the in vivo measurements of the oxygen content in the arterial blood of dogs over a period of 10 h. The dots represent the batch gas analysis performed with a Nova Biomedical blood gas analyzer. The solid lines represent the analyses monitored by the instrument. Blood oxygen measurements were obtained continuously (not shown in the figure) about every 3 sec. Two different polymer solutions are shown. The measurements performed by the instrument are not affected by the presence of unmetabolized clots and/or anesthetics in the blood stream. Additionally, no deterioration of the signal was found after 10-h periods. 

J. R. Alcala, I. Scott, J. Parker, B. Atwater, C. Yu, R. Fischer, and K. Bellingrath, Real time frequency-domain fiber optic sensor for intra-arterial blood oxygen measurements, in SPIE 1885, Proceedings of SPIE Biomedieal Optics (J. R. Lakowicz, ed.), Los Angeles, pp. 306-316 (1993). 

Figure 13.1. A typical Clark electrode for oxygen measurement (Adapted from Ref. I.)...

The current method measures water vapour indirectly based on oxygen measurements in wet and dry flue gas. There are two disadvantages with this solution (a) the measurement uncertainty is relatively high it is very sensitive to system errors, for example bad calibration (b) if hydrocarbons are present in the flue gas they will interfere with the water vapour analysis. 

The evolution of the a elements is well understood (except for the latest oxygen measurements in halo stars, which are still uncertain), assuming that iron is produced by type la supernovas in the galactic disk as well as by type 11 supernovas. 

Filling the Gas Meter with Oxygen. Measure the volume of the meter. Write the equation of potassium permanganate decomposition. Calculate how many grammes of the salt have to be taken for the evolved oxygen to fill the gas meter up to two-thirds of its volume. 

Historically, the alpha factor, a, was developed from oxygen mass transfer studies in the aerated basins of municipal waste water treatment plants. It thus denotes the ratio of the mass transfer coefficient for oxygen measured in the waste water (WW) to that measured in tap water (TP). 

The oxygen measured in the stack is the sum of the unused oxygen from the firebox plus the oxygen from tramp air, drawn into the convective section and stack. 

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