Organic Liquid Scintillators

Organic Scintillators and Liquid Scintillation Counting , Academic Press, NY (1971)... 

Hirayama, F. Lipsky, S. Saturated Hydrocarbons as Donors in Electronic Energy Transfer Processes New York. In Organic Scintillators and Liquid Scintillation Counting Horrocks, D.L., Peng, C.-T., Eds. Academic Press, 1971 205 pp. 

Low-Level Waste Low-level waste (LLW) consists of contaminated dry trash, paper, plastics, protective clothing, organic liquids such as liquid scintillation samples, and the like. LLW is produced by any facility that handles radioactive materials such as nuclear power plants, medical facilities, colleges, and so forth. In the United States, commercial LLW is sent to one of three disposal sites (Barnwell, South Carolina, Richland, Washington, and Clive, Utah). Due to the limited size of these sites (and similar disposal sites through the world) and steeply escalating costs for waste disposal, the primary goal of LLW treatment prior to disposal is volume reduction, either by incineration or compaction, followed... 

There are three common types of organic scintillator. The first type is a pure crystalline material, such as anthracene. The second type, the liquid scintillator, is the solution of an organic scintillator in an organic liquid, such as a solution of p-terphenyl in toluene ( 3 g solute/L solution). The third type is the solution of an organic scintillator, such as p-terphenyl, in a solid plastic, such as polystyrene. 

Horrocks, D. L., and Peng, C. (1971). Organic Scintillation and Liquid Scintillation Counting. New York Academic Press. 

Scintillators Materials used for the measurement of radioactivity, by recording the radioluminescence. They contain compounds (chromophores) which combine a high fluorescence quantum efficiency, a short fluorescence lifetime, and a high solubihty. These compounds are employed as solutes in aromatic Hquids and polymers to form organic liquid and plastic scintillators, respectively. 

D. S. Tinti and M. A. El-Sayed, Organic Scintillators and Liquid Scintillation Counting, Academic Press, New York (1971), p. 563. 

In both scintillator and gas detectors, the absorption of radiation causes excitation and ionization however with the scintillation process, the absorbed energy produces a flash of light, rather than a pulse of current. The principal types of scintillation detectors found in the clinical chemistry laboratory are the sodium iodide crystal scintillation detector and the organic liquid scintillation detector. Because of the crystal detector s relative ease of operation and economy of sample preparation, most clinical laboratory procedures have been developed to measure nucfides, such as which can be counted efficiently in a crystal detector. A liquid scintillation detector is used to measure pure (3-emitters, such as tritium or C. 

Each animal was sacrificed by captive bolt after the appropriate withdrawal interval (4, 6, 14 and 28 days after the 2nd dose) and processed as in an abattoir. The entire liver, kidneys and udder were excised and 1-2 kg samples of muscle from both the flank and the udder diaphragm and 1-2 kg samples of fat from the abdominal area were collected. Each organ and tissue was minced and processed three times through a commercial meat grinder to prepare respective homogenate samples. Sub-samples (200-300 mg) were prepared in triplicate for total residue analysis. Total radioactivity concentrations, expressed as pirlimycin free base equivalents, were determined by direct liquid scintillation counting (liquids) or combustion analysis (solids) following standard techniques. 

The organic liquid scintillators consist of a mixture of a solvent with one or more solutes. Compounds that have been used successfully as solvents include xylene, toluene, and hexamethylbenzene (see Table 6.2). Satisfactory solutes include p-terphenyl, PBD, and POPOP. 

In addition to sodium iodide crystals, a number of organic scintillators such as stilbene, anthracene, and terphenyl have been used. In crystalline form, these compounds have decay times of 0.01 and O.l ps. Organic liquid scintillators have also been developed and are used to advantage because they exhibit less selfabsorption of radiation than do solids. An example of a liquid scintillator is a solution ofp-terphcnyl in toluene. 

The measurement of the radon content of water is based on extraction processes that exploit the high partition coefficient of radon either between gas and water or between organic liquid scintillators and water. In particular, by introducing fine gas bubbles to water, it is possible to extract radon very efficiently. Radon is thus bubbled out from water and collected in a Lucas cell. The detection limit for this method is very low, 50Bqm . ... 

The scintillation process in an organic liquid scintillator (From Kessler 1989 used by permission of Perkin Elmer)... 

Scintillators which have hydrogen as a constituent, such as organic liquids for example, may be used for fast neutron detection, since the protons produced by fast neutron collisions create the ionization required to operate the detector. In order to adapt a sodium iodide scintillator for the detection of slow neutrons, a small concentration of boron may be distributed in the crystal, giving a particles on neutron capture as discussed above. Alternatively, it is possible to add a neutron absorber which emits 7 rays following the (n, y) capture reaction. Another possibility is the use of lithium iodide (Lil) which, in addition to its own suitability as a scintillator, interacts with neutrons through the reaction... 

Where it is required to measure neutrons in the presence of a significant y-ray background, it is possible to make use of the properties of certain scintillators to distinguish the pulses produced by neutrons from those due to y rays. This is known as a pulse-shape discrimination (PSD) system. In stilbene and some organic liquid scintillators, the pulse rise time for the fluorescence caused by the secondary electrons from a y-ray interaction is considerably shorter than that due to the recoil protons produced by neutron scattering. By the use of fast timing discriminators, it is possible to separate the pulses caused by neutrons from those due to the y rays. 

Separate solid and liquid wastes. Radioactive wastes must be separated into solids (absolutely no liquids are permitted) and liquids. Liquid wastes must be kept separate according to chemical reactivity. For example, do not mix wastes containing acids with liquids containing bases, and do not mix aqueous liquids with organic liquids. Keep flammable organic solvent radioactive wastes in safety cans. Animal carcasses and liquid scintillation vials are also kept separate. 

Laser dye. Organic liquid scintillator. Lemon yellow plates with blue green fluorescence (cyclohexane). Mp 178°. 

The emitted P particles excite the organic molecules which, in returning to normal energy levels, emit light pulses that are detected by a photomultiplier tube, amplified, and electronically counted. Liquid scintillation counting is by far the most widely used technique in tritium tracer studies and has superseded most other analytical techniques for general use (70). 

Ross HJE, Noakes E, Spalding JD. Liquid Scintillation Counting and Organic Scintillators, Lewis, Chelsea, MI, 1991. 

DDT Metabolism.-- The metabolism of DDT has been studied in R and S fish, following similar protocols to chlorinated cyclodiene metabolism organic extraction (acetonitrile), thin layer chromatography of organic extracts, and liquid scintillation counting of the resultant spots (4). When S and R fish were exposed to 60 yg/l of 14C-labelled , -DDT for 4 hr, radioactivity was found in the spots which co-chromatographed with... 

Both the organic and water layers from the radioactive insecticides were counted in a liquid scintillation counter (Isocap/300, Searle). The results are expressed as nanomoles or micrograms equivalent of the substrate per mg protein. 

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