Detector radioactivity

Radioactivity detectors, which count the number of nuclei that decay, provide an example of a conversion from number of particles to moles. If a radioactivity measurement on a blood sample from a patient receiving radiation... 

Gas ionization detectors are widely used in radiochemistry and X-ray spectrometry. They are simple and robust in construction and may be employed as static or flow detectors. Flow studies have received attention in the interfacing of radioactive detectors with gas chromatographs. A radio-gas chromatograph (Figure 10.9) uses a gas flow proportional counter to monitor the effluent from the gas chromatography column. To achieve... 

A radioactivity detector is used to measure radioactivity in the HPLC eluent, using a flow cell. The detection principle is based on liquid scintillation technology to detect phosphors caused by radiation, though a solid-state scintillator is often used around the flow cell [17,31]. This detector is very specific and can be extremely sensitive. It is often used for conducting experiments using tritium or C-14 radiolabeled compounds in toxicological, metabolic, or degradation studies. 

Traditional exploration for sandstone-type uranium deposits has centered on genetic models and radiometric methods (Morse 1969 Harshman 1970 Rubin 1970). However, these methods have become prohibitive for sandstone-type uranium deposits hidden at a depth of hundreds of metres (Riese et al. 1978). Radioactivity detectors are ineffective in regions where there is a relatively thin inactive overburden (Bowie etal. 1970). 

Frey BM, Frey FJ. Three radioactivity detectors for hquid-chromatographic systems compared. Clinical Chemistry 28, 689-692, 1982. 

Nassar AEF, Bjorge SM, Lee DY. On-line liquid chromatography-accurate radioisotope counting coupled with a radioactivity detector and mass spectrometer for metabolite identification in drug discovery and development. AnaZyft caZ Chemistry 75, 785-790, 2003. 

Figure 4.38 Schematic illustration of a self-diffusion experiment in which (a) a thin layer of radioactive nickel is deposited on one surface of a nonradio active nickel specimen. After heating and time (b), the radioactive nickel has diffused into the sample, as monitored with a radioactive detector. From K. M. Ralls, T. H. Courtney, and J. Wulff, Introduction to Materials Science and Engineering. Copyright 1976 by John Wiley Sons, Inc. This material is used by permission John Wiley Sons, Inc.

Boemsen, K. O., Floeckher, J. M., and Bmin, G. J. M. (2000). Use of a microplate scintillation counter as a radioactivity detector for miniaturized separation techniques in drug metabolism. Anal. Chem. 72 3956-3959. 

The CdTe radioactivity detector was computer interfaced to a laboratory microcomputer (IBM PC-XT) by using the open collector... 

Our second on-line radioactivity detector consisted of a plastic scintillator material (BC-400, Bicron Corp., Newbury, OH) that was machined from 1-inch-diameter rod stock into a 5/8-inch-diameter (front face) solid parabola (see Figure 2). A special rotating holder was constructed for the plastic scintillator and the curved outer surfaces were coated by vacuum deposition with a thin film of aluminum in order to reflect the emitted light toward the front face of the scintillator. A detection length of 2 mm was defined within the parabola by aluminum mounting rods (0.250 inch outer diameter) that were press-fit (coaxial to the separation capillary) in the sides of the scintillator, as illustrated in Figure 2. 

Regardless of cell size, the faster you push a radioactive peak through the cell, the smaller that peak will appear to the radioactivity detector (Figure 5). Thus low level samples cannot be run at high flow rates. With the usual 4.6mm x 25cm HPLC columns, flow rates of 0.5-1.0ml/min. are used routinely with no difficulty. 

Analog versus Digital. Most detectors produce analog (continuous) signals that must be digitized before they can be manipulated by a digital computer. The main exception is the radioactive detector. 

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