Oxygenated optical density

Figure 13.13. Dependence of the phase angle on signal amplitude at fixed oxygen concentration. The optical densities of the filters used to attenuate tbeexcitation are as indicated on the steps. The phase angle readout remained essentially constant except foe very low signal amplitudes.

These optical probes are the most universally applicable in situ devices for on-line biomass monitoring up to now [15,16]. Konstaninov et al. [17] tested several absorbance and scattering sensors for real-time biomass concentration monitoring in mammalian cell cultivation processes and Hatch and Veilleux [18] compared optical density probes with oxygen uptake rates, packed cell volume, and off-line cell mass monitoring in commercial fed-batch fermentations of Saccharomyces cerevisiae [19]. In order to minimize influencing effects, special chemometric data treatment is necessary [20]. 

Fig. 10. Growth and metabolite production of the marine strain Hel45. OD546 Optical density at 546 nm p02 oxygen partial pressure...

In addition to the shock wave velocity it is necessary, in a system where the density does not uniquely determine the composition (and this includes all but the very simplest chemical systems of interest), to measure some concentration function in order to follow the reaction. This is one of the greatest experimental difficulties associated with the method, since the changes occur so rapidly. Where possible, the concentration change is followed spectrophotometrically. This concentration monitoring is the second function of the observation points in Fig. 3. Especially for species with line spectra, the small optical density change, coupled with the fast response-time necessary, excludes the use of a conventional spectrophotometer. An example of a detection system which has been used for the hydrogen/oxygen... 

ASTM E 906 Heat and Visible-Smoke-Release Rate Test (based on Ohio State University Release Rate Apparatus). In this test the specimen is injected into an environmental chamber through which a constant flow of air passes. A radiant-heat source is used to produce the desired heat flux in the specimen, which way be tested horizontally or vertically. Combustion may be initiated by a number of different methods. The changes in temperature and optical density of the gas leaving the chamber are monitored, and from the resultant data the heat-release rate and visible anoke-release rate are calculated. Toxic-gas release and oxygen consumption rates may also be measured. 

Prepare an analar solution of 12 g ammonium ferric sulphate in water and add 40 ml of analar nitric acid. Dilute to 100 ml. Prepare a solution containing 0.4 g of mercuric thiocyanate crystals in 100 ml of absolute alcohol. Mix 5 ml of the test solution from the oxygen flask combustion method (described above) with the ammonium ferric sulphate solution. Add 1.5 ml of mercuric thiocyanate solution. When chlorine is present an orange to red colour will develop in the test sample. If a semi-quantitative estimation of chlorine is required, set the solution aside for 10 min, then measure the optical density of this coloured solution against the blank solution at 460 nm in 20 mm cells. Typical calibration figures for the examination of plastic coatings such as PVC are as follows ... 

The hemolysate (Section 3.2) was further diluted with 0.7% Sterox SE solution until an optical density of about 0.400, measured at X = 677 nm in a layer thickness of 0.0128 cm, was reached. Of this solution 10 ml was brought into a revolving glass tonometer which was 30-cm long. The tonometer was continuously flushed with pure oxygen (1 liter/min) for... 

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