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Preparation of Samples for Liquid Scintillation and Gamma Counting
Published in Howard J. Glenn, Lelio G. Colombetti, Biologic Applications of Radiotracers, 2019
If tissue samples are digested in acid media, the possibility of decarboxylation and the loss of radioactive carbon dioxide exists. Therefore most solubilization is done under alkaline conditions. When tissue samples are digested by alkaline substances, heme and other pigments often cause colored solutions giving rise to various degrees of quenching. Color quenching is most severe with the red and yellow end of the spectrum, as the photomultiplier tubes in the liquid scintillation counters are most sensitive to the blue end of the spectrum.22 Bleaching is used to reduce coloration. The most commonly used bleaching agents have been hydrogen peroxide and benzoyl peroxide, the former apparently causing less chemiluminescence23 and the latter being the most effective and causing the least overall quenching.4, 19, 22 Other bleaching agents used have been chlorine water, strong sunlight, ethanolic sodium borohydride, sodium hypochlorite, bromine water, trioctyl ammonium borohydride, and ultraviolet irradiation. When hydrogen peroxide or benzoyl peroxide is used, the reaction can be run in the counting vial. Care must be taken to see that substances that can be oxidized to a volatile form are not lost. Residual oxygen from peroxide oxidation in scintillation solutions causes quenching and must be removed. This can be done by the use of an enzyme catalyst or a reducing agent (oxygen scavenger) such as a 5 to 10% solution of ascorbic acid or a 4% solution of stannous chloride in 0.1 N hydrochloric acid.24
Tissue Preparation for Liquid Scintillation and Gamma Counting — the Counting Processes
Published in Lelio G. Colombetti, Principles of Radiopharmacology, 2019
Howard J. Glenn, Lelio G. Colombetti
When tissue samples are digested by alkaline substances, heme and other pigments often cause colored solutions giving rise to various degrees of quenching. Color quenching is most severe with the red and yellow end of the spectrum as the photo-multiplier tubes in the liquid scintillation counters are most sensitive to the blue end of the spectrum.18 Bleaching is used to reduce coloration. The most commonly used bleaching agents have been hydrogen peroxide and benzoyl peroxide, the former apparently causing less chemiluminescence19 and the latter being the most effective and causing the least overall quenching.5,18 Other bleaching agents used have been chlorine water, strong sunlight, ethanolic sodium borohydride, sodium hypochlorite, bromine water, trioctyl ammonium borohydride, and ultraviolet irradiation. When hydrogen peroxide or benzoyl peroxide is used, the reaction can be run in the counting vial. Care must be taken to see that substances that can be oxidized to a volatile form are not lost. Residual oxygen from peroxide oxidation in scintillation solutions causes quenching and must be removed. This can be done by the use of an enzyme catalyst or a reducing agent (oxygen scavenger) such as a 5 to 10% solution of ascorbic acid or a 4% solution of stannous chloride in 0.1 Nhydrochloric acid.20
Technetium-Labeled Compounds
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
Suresh C. Srivastava, Powell Richards
Technetium can be effectively separated by precipitation as Tc2S7. The sulfide is extremely insoluble and as little as 3 μg/mí can be precipitated from up to 4 N HCl or 8 NH2SO4.440 To ensure that all technetium is present as Tc(VII), bromine water is usually added. At elevated temperatures the precipitation is rapid and quantitative. When rhenium and ruthenium are present, the separation method involves additional steps. As mentioned in an earlier section, tetraphenylarsonium or tetraphenylstibon-ium chlorides are very effective précipitants for pertechnetate, especially from basic solutions. The precipitates can be dissolved in alcohol and further separation of technetium carried out by ion exchange (from rhenium which also precipitates and from traces of ruthenium). Several other précipitants have also been developed and used.23
Inhibitory effects of taraxasterol and aqueous extract of Taraxacum officinale on calcium oxalate crystallization: in vitro study
Published in Renal Failure, 2018
Mahboubeh Yousefi Ghale-Salimi, Maryam Eidi, Nasser Ghaemi, Ramezan Ali Khavari-Nejad
Sodium tungstate (100 g) and 25 g of sodium molybdate were dissolved in 800 mL of water in a 1500 mL flask. Then, 50 mL of phosphoric acid and 100 mL of HCl were added and refluxed for 10 h. After cooling and adding 150 g of lithium sulfate, 50 mL of water and 4–6 drops of bromine water were added and allowed to stand for 2 h. Then, the solution was boiled for 15 min and cooled before filtration. The reagent should have no greenish tint [18].