High liquid scintillation counting

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. 

On the other hand, nonspecific analytical methods (such as liquid scintillation counting, spectrophotometry, and titration procedures) may not distinguish between the solute under study and certain impurities. When using such methods, the solid state of interest should be highly pure and the amount of solid in excess of that required to saturate the solution should be minimized. 

Commonly, in vitro determination of HDAC activity is a manual assay utilizing a coupled two-step process, including enzymatic deacetylation of a substrate followed by reaction termination and readout [10]. Assays utilize nuclear extracts and substrates containing labeled (radioactive or fluorescent) acetylated histones. For the isotope-based assays, the enzymes are incubated with acetate-radiolabled histones prepared from chicken reticulocytes or chemically [ Hjacetylated peptide substrates, and the enzymatic activity is determined by liquid scintillation counting [11]. Alternatively, histones may be obtained from cells following treatment with [ H]acetyl-CoA [12]. The caveats of these approaches include the variability of prelabeled acetylated core histones within preparations, potential high costs, their labor-intensive nature and the presence of radioactive waste. 

Moody, R.P., Carroll, J.M., Kresta, A.M.E. (1987) Automated high performance liquid chromatography and liquid scintillation counting determination of pesticide mixture octanol/water partition rates. Toxicol. Ind. Health 3, 479 -90. 

Tritium as a low energy beta-emitter is most conveniently measured by liquid scintillation counting. In general, the tritium measurement is the most complicated of all the radionuclide labels. The difficulties are related to the character of the sample which is tritium labeled. Tritium labeling is not suitable in all cases ir. which the system yields high chemiluminiscence the samples are coloured or turbid. Recently, however, new types of liquid scintillation counters appeared which make it possible to count tritium even under such complicated conditions (Beckman, Packard, Kontron, Berthold). 

The main advantage of liquid scintillation counting is the relatively high counting efficiency, which can amount to about 90 to 100%. 

Liquid scintillation counting of high-energy beta emitters - beta particles with energies greater than 1 MeV can be counted in water (Cerencov radiation), with no requirement for additional fluors (e.g. 52P). 

Tritium is measured by liquid scintillation counting of a portion of a distilled sample. Several reagents (such as sodium sulphite and silver iodide) can be added in the distillation to prevent interference by radioiodine. The allowed concentration of tritium in water for human consumption is relatively high thus the method presented here is normally adequate for routine determinations. However, if required, lower concentrations of tritium in water can be determined by electrolytic enrichment. The principles of the tritium determination procedure are as follows. 

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