Liquid scintillation techniques

Centrifugation alone is not sufficient to separate Np solid material from the solution (j) ). Thus, the Np solution concentrations and oxidation state analyses were determined from aliquots filtered through approximately 1.8 nm pore-size Centriflo membrane cones (Amicon Corp., Lexington, MA). Each filter cone was pretreated with an initial aliquot of the suspension to be filtered. Tests using successive filtration confirmed that no significant amounts of Np were being sorbed by the filter cones. The solutions were alpha counted by liquid scintillation techniques. Major cations in the solutions were determined by inductively coupled plasma spectrometry (ICP) analyses. 

Calcium chloride solutions (pH =6.2) labeled with Ca or 36ci were displaced vertically downward through columns of homogeneous, repacked, water-saturated sandy soil by a chemically identical solution labeled with Cl or Ca, respectively. Constant water fluxes, and solution activities of 1 to 15 pCi/dm, were used. Calcium solutions were analyzed by titration with disodium dihydrogen ethylenediamine tetraacetate to a murexide end point (11). The activity of radioactively labeled solutions was obtained by liquid scintillation techniques. Concentrations of adsorbed calcium were calculated from isotope dilution. The concentration of calcium chloride in the influent solution was 0.08 N. Because exchange of calcium for itself was the only chemical process affecting transport, the calcium chloride concentration remained constant at 0.08 N throughout each experiment, both within the column and in the effluent. 

The pressure is released after a suitable time interval, and the contents of the chambers are sampled using syringes and PTFE tubing. It is important to keep the cell thermally stable during the sampling to avoid temperature-induced flows. The drop in pressure has two effects. It causes a cooling of the cell contents and a small but unavoidable amount of bulk flow of material from top to bottom. It is therefore essential to stir the cell for several minutes after reaching ambient pressure, to attain thermal stability and to ensure a uniform composition of the bottom compartment. The concentrations of labelled material in the compartments are determined by liquid-scintillation techniques. The effects of the bulk flow must be taken into account, and equations have been developed for this purpose. ... 

Liquid scintillators have a wide use for routine measurement of jU-emitters, particularly low-energy ones like and C, in liquid samples, especially in biochemistry and in hospitals. Since these isotopes are very important in biochemical applications, most of the development of liquid scintillation technique has been focused on them. 

Radioactivity was measured by liquid scintillation techniques with a Tri-Carb model 3003, using Insta-Gel as the cocktail, both of which were manufactured by Packard Instruments. 

The solutions were analyzed periodically by extracting an acidified aliquot with ethyl acetate and counting the radioactivity in the extract by liquid scintillation techniques. Paper chromatography of the extract with the benzene/propionic acid/water solvent system used in Case 4 confirmed the purity and identity of the picloram in the extract. The results of the analyses are shown in Table V. 

The liquid scintillation technique was utilized in the case of thymidine or DNA labelled with or Measurements in the homogeneous phase have shown that the counting efficiencies depend on two variables the 3 particles energy and the size of the molecule carrying the radioisotope. In the homogeneous phase, measurements are correct only if the liquid scintillation medium and the radioactive solution added give rise to a medium which is homogeneous, not only at the macroscopic level, but also at the molecular level. Experiments performed have shown that, for small sized molecules (like... 

Ei t ml of the extracted water is added to 12 ml of scintillation cocktail (Moghissi et al., 1973) and the tritium activity is then determined. Because of the nature of this conference, it should be stated that the liquid scintillation technique used is common. Nevertheless, this biological assay of soil vitality is possible only because of liquid scintillation counting of tritium and is being reported because we feel that it constitutes a new and exciting technique in soil analysis. 

Cocktail preparation difficulties and expense are also eliminated when using the detectors as opposed to standard liquid scintillation techniques in which such problems as chemiluminescence and quenching are often encountered (10). 

This enzyme catalyses the reaction which is the Hrst in the sequence which leads to the synthesis of pyrimidines. It may be assayed radiochemically (279) by using labelled carbamoylphosphate. The reaction mixture is acidified and heated to eliminate residual substrate as 002 and the acid stable product counted by liquid scintillation techniques. 

PPO and POPOP are among the most commonly used organic primary and secondary fluors, respectively. Despite their high efficiencies in both liquid and plastic scintillators, one limitation is their incompatibility with hydrophilic reagents. In liquid scintillation techniques, an efficient extraction of radioactive nuclides into the organic phase where PPO and POPOP dissolve is often mandatory. In neutron detection by plastic scintillators, the use of an efficient, yet hydrophilic, neutron absorber, Li, is strictly limited if not prohibited. 

Toribara et al. used a liquid scintillation technique for counting Pu from bio-... 

S-hydroxyheptadecatrienoic acid by studies of its vial surface adsorption using high-performance liquid chromatography and liquid scintillation technique. Chem. Phys. Lipids 99, 95-101. 

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