Scintillation counting cocktail

Econofliior-2. [DuPont/Medical Prods.] liq. scintillation counting cocktail... 

Commercially available, highly efficient liquid and solid scintillators were tested as standards for comparison with our samples. Ultima Gold (PerkinElmer) is a standard liquid scintillation counting cocktail, containing PPO (ca. 1 wt %) in a mixture of aromatic compounds, and phosphate and succinate surfactants. BC-400 (Bicron) is a plastic scintillator composed of organic fluors, PPO and POPOP, at <3 wt % in PVT. KG2 (Bicron) is a cerium-activated lithium silicate glass scintillator, containing 7.5 wt % of Li (95% i) as a neutron absorber, and Ce as a scintillation material. 

Liquid scintillation counting is by far the most common method of detection and quantitation of -emission (12). This technique involves the conversion of the emitted P-radiation into light by a solution of a mixture of fluorescent materials or fluors, called the Hquid scintillation cocktail. The sensitive detection of this light is affected by a pair of matched photomultiplier tubes (see Photodetectors) in the dark chamber. This signal is amplified, measured, and recorded by the Hquid scintillation counter. Efficiencies of detection are typically 25—60% for tritium >90% for and P and... 

Liquid scintillation counting has been used frequently for the measurement of environmental technetium. The specimens to be analyzed are treated by chemical procedures to obtain a technetium-bearing sample solution, which is mixed with a cocktail for scintillation counting. A low background scintillation counter with an anticoincidence system can be used for high precision measurements at a detection limit of 1-25 mBq. 

Measurement of radioactive decay can also be affected by various components present in, or added to, the scintillation cocktail. These components can cause quenching that is, they can decrease the efficiency of the scintillation process. Scintillation counting provides data in counts per minute (cpm). Quenching dictates that the counts per minute detected is less than the actual decay rate, or disintegrations per minute (dpm). Almost every sample encountered experimentally is quenched to some degree for example, 02 picked up by the scintillation fluid from contact with air serves as a quencher. Therefore, researchers frequently count an additional sample containing a standard of known de-... 

Incomplete solubility and associated point quenching constitute a major problem in scintillation counting. Efficient scintillation counting requires that the sample be fully soluble in the excitable organic solvents of the scintillation fluid. However, biological systems, which are usually aqueous systems or assays, frequently contain water or hydrophilic molecules that will not dissolve in standard toluene-based scintillation cocktails. 

After solubilisation, the sample is added to a sdntillation cocktail suitable for aqueous solutions. Solubilisation of tissues often produces chemiluminescent materials which can distort measurements of radioactivity. To reduce or remove this problem, it is recommended that samples should be kept in the dark before counting. An expensive alternative to scintillation counting for tissue samples, and one which is only justified when handling highly repetitive samples, is combustion of the sample in an appropriate furnace the 14C and 3H labelled material is converted respectively into C02 and H20 which are collected in suitable wash bottles. 32P label is converted into phosphate which remains in the ash following combustion. 

For liquid scintillation counting (LSC), a Packard Tri-Carb 460 CD microprocessor controlled liquid scintillation spectrometer, with automatic external standarization, quench correction, and conversion of counts per minute (cpm) into disintegrations per minute (dpm), was utilized. An appropriate scintillation cocktail was selected according to sample characteristics Insta-Gel II (Packard) was used for aqueous solutions and organic extracts, Dimilume-30 (Packard) for NaOH solutions and... 

Analyses. Liquid scintillation counting was used to measure the Pu activity in all samples. Aqueous samples (1.00 or 2.00 ml) were added to 18 ml of Insta-Gel scintillation cocktail (Packard Instrument Co.) in glass scintillation vials and thoroughly mixed. A Packard Tri-Carb Model 1550 liquid scintillation analyzer was used to count all the samples. 

As discussed in Chapter 7, a source may also be deposited by volatilization or electrodeposition for alpha or beta particle counting by Si diode or proportional counter, or added as a solution or suspension to scintillation cocktail for liquid scintillation counting. For electrodeposition, as indicated by Eq. (3.20), the... 

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