Continuous flow radioactivity

Figure 29. Diagram of an HPLC fitted with a continuous-flow radioactivity detector.

There are many potential advantages to kinetic methods of analysis, perhaps the most important of which is the ability to use chemical reactions that are slow to reach equilibrium. In this chapter we examine three techniques that rely on measurements made while the analytical system is under kinetic rather than thermodynamic control chemical kinetic techniques, in which the rate of a chemical reaction is measured radiochemical techniques, in which a radioactive element s rate of nuclear decay is measured and flow injection analysis, in which the analyte is injected into a continuously flowing carrier stream, where its mixing and reaction with reagents in the stream are controlled by the kinetic processes of convection and diffusion. 

Browne TR, Szabo GK, Ajami A, Wagner D (1993). Performance of human mass balance/metabolite identification studies using stable isotope (13C, 15N) labeling and continuous-flow isotope-ratio mass spectrometry as an alternative to radioactive labeling methods. J Clin Pharmacol 33 246-252... 

Pancreatic juice collected over an extended period of time by a permanent fistula may be considered an ideal material for studying the net synthesis of a series of well-defined proteins. As soon as radioactive proteins are present in zymogen granules they may appear in the juice after a certain delay, which depends upon the conditions of the next stimulation. When rats in which a continuous flow of juice is promoted by secretin or... 

Two other filtration modules, which both formed part of automated radioimmunoassay systems, have been developed. - One of these, was based on conventional continuous flow techniques. At the filtration stage, a continuously moving strip of glass fiber filter paper was strengthened and wetted, the reaction mixture was filtered, and the precipitate was washed by two streams of buffer. The strip was dried and overlaid with cellulose adhesive tape before being counted as it passed between two end-window radioactivity detectors and wound onto a take-up spool. In the second system, glass fiber filter disks are mounted at intervals over perforated segments of a flexible plastic carrier tape. The contents of five... 

As a matter of fact, the problem of radioactive decay is exactly the same as the problem of washout of particles from a perfectly mixed, continuous flow vessel. Thus, Eq. (124) of the text can be applied to yield the well-known law of radioactive decay. 

Another advantage of radioactive tracers is their ease of detection and determination. The radiating properties of the tracers are not affected at all by the physical and chemical condition of the sample, i.e., temperature, pressure, presence and concentration of chemicals, and so on. This exempts one from laborious preparation and treatment of the sample before measurement. In the measurement of a nuclide emitting a y ray, all one has to do is to put the sample near a detector and press a button to operate the electronic system. Radioactive tracers are also suitable for continuous-flow detection and some of them further for imaging. 

The VFS must provide intermittent flow of outdoor air to purge the containment atmosphere of airborne radioactivity during normal plant operation, and continuous flow during hot or cold plant shutdown conditions to provide an acceptable airborne radioactivity level prior to personnel access. 

The off gas from a boiling water nuclear power reactor contains a whole variety of radioactive trash, one of the most troublesome being Xe-133 (half life = 5.2 days). This off gas flows continuously through a large holdup tank in which its mean residence time is 30 days, and where we can assume that the contents are well mixed. Find the fraction of activity removed in the tank. 

Water containing a short-lived radioactive species flows continuously through a well-mixed holdup tank. This gives time for the radioactive material to decay into harmless waste. As it now operates, the activity of the exit stream is 1/7 of the feed stream. This is not bad, but we d like to lower it still more. 

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