Geiger counter, thin-window

Adsorption onto activated charcoal (Norit A) has been used for small oligonucleotides, up to tetranucleotides (Crane and Lipman 1953 Mandeles and Kammen 1966). The method is quicker and more convenient than DEAE-cellulose chromatography. Mandeles and Kammen (1966) used Norit A suspended in 1 mM phosphate 1 mM pyrophosphate buffer at pH 6.0 at a concentration of 100 mg/ml. The nucleotide solution is adjusted to pH 3 and 5 mg Norit for every optical density unit ( 40 pg) of nucleotides is added. The charcoal is collected on a filter paper and washed with water. (A good quantitative measure of or radio-activity may be obtained by counting the dry filter paper in a Geiger-Muller thin window counter.) The nucleotide material is eluted with a small volume of a mixture of ethanol, water and ammonia (600 400 6.5 v/v/v) which is then removed by drying under reduced pressure at 40°C. 

All gaseous sulfur products obtained as a result of incubation of sulfur-treated fruit were oxidized with alkaline hydrogen peroxide, precipitated as barium sulfate, and counted with a thin window Geiger counter. The peel and peel proteins were oxidized with magnesium nitrate, the sulfur was precipitated as barium sulfate according to standard methods, and counted as in the case of the gaseous products. Counting data, as reported, are fully corrected. 

Seimiya, T., K. Sekine, and T. Sasaki Counting of tritium with a thin windowed Geiger-Miiller counter tube. J. Scient. Instr. 42, 906... 

A common gas ionization counter is the Geiger-Miiller counter (Figure 26-5). Radiation enters the tube through a thin window. Windows of different stopping powers can be used to admit only radiation of certain penetrating powers. 

Isotopic. Sulfur-35 emits j8-particles of 0.167 M.e.v. maximum energy and has a half-life of 87.1 days. It is readily assayed as a solid with a thin-mica-end-window Geiger counter. 

Isotopic. Iron-55 is an electron-capture isotope with a half-life of 2.94 years. Iron-59 is a mixed /3-7 emitter the main radiations of which areO.27 M.e.v. 8 (46%), 0.46M.e.v. /8 (54%), 1.10 M.e.v. 7 (57%), and 1.29 M.e.v. 7 (43%). The half-life of Fe is 45.1 days. The radioactive samples are most readily assayed with a standard thin-mica-window Geiger counter which will detect mainly the Fe /3-particles. Decomposition of ferrocene and ferricinium salts in a boiling mixture of four parts by volume of concentrated nitric acid and one part of 75% perchloric acid and the subsequent electrodeposition of iron on copper disks gives samples which exhibit excellent counting reproducibility. 

Fig. 7.3 A Geiger counter tube. Radiation which passes through the thin window ionizes the gas in the tube. The electrons are accelerated by the high voltage creating (500-1,200 V), creating a pulse which is detected electronically...

Solid samples containing high-energy p emitters can be measured with end-window Geiger-Muller counters, whereas proportional counters are suitable for the measurement of a and p emitters. Self-absorption of a and p rays in solid samples may play an important role and requires special attention in the case of a and low-energy p radiation. Very thin and homogeneous layers can be obtained by electrolytic or vapour deposition of the radionuclides to be measured or by solvent extraction and subsequent evaporation of the solvent. 

A. With these radio-autographs as guides, the corresponding paper strips are cut into squares or, where necessary, rectangles, in such a way as to avoid having parts of different penicillin zones on the same square. The squares are then fitted into planchettes and measured ra-diometrically in a thin end-window Geiger-Miiller counter. From the total counts for each penicillin species, the proportions by weight (more strictly, the molar proportions) can readily be calculated... 

Stick with sellotape a piece of Sr (pure p emitter) ( Sr) foil to a thick aluminium plate (AI) ( 5 mm thick) and hold it in position (with thick tape) to a thin aluminium plate which fits just under the end-window of a Geiger-MOller (G-M) counter inside its lead castle. The Sr foil will be separated from the counter by thick aluminium which absorbs its p particles. Both aluminium plates have a circular hole opposite the end window of the counter. (See Fig. 18.1)... 

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