Scintillation counter radioactivity

RECOVERY. A dual label recovery experiment, from plasma and PBS, was performed using 3H-all trans and 14C-cis retinoic acid. The normal extraction procedure was followed up to and including the HPLC purification step. No LC/MS analysis was performed. Aliquots were taken and total radioactivity determined after extraction and derivatization. Fractions (0.5 ml) from the HPLC were collected and counted. Counting was performed using a Beckman Model LC3801 liquid scintillation counter. Radioactivity was corrected for spillover and quench. 

There are two separate units of radioactivity in use, the first being the Curie (Ci) which is defined as an activity of 3.7 x 10 ° disintegrations per second. This is a large unit — bear in mind that with a modern day liquid scintillation counter radioactivity levels down to a few hundred coimts per minute can be easily measured — so it is very coimnon to use smaller subunits such as the millicurie (10 Ci) and the microcmie (10 Ci). The second, and more recently introduced miit, is the Becquerel (Bq). At one disintegration per second this is an extremely small amoimt of radioactivity. The conversions are... 

Geiger-Muller counter scintillation counter radioactive dating... 

Radiometric ore sorting has been used successfully for some uranium ores because uranium minerals emit gamma rays which may be detected by a scintillation counter (2). In this appHcation, the distribution of uranium is such that a large fraction of the ore containing less than some specified cut-off grade can be discarded with tittle loss of uranium values. Radioactivity can also be induced in certain minerals, eg, boron and beryllium ores, by bombarding with neutrons or gamma rays. 

Deuterium oxide [7789-20-0] M 20, f 3.8°/760mm, b 101.4°/760mm, d 1.105. Distd from alkaline KMnOa [de Giovanni and Zamenhof Biochem 7 92 79 I963. NOTE that D2O invariably contains tritiated water and will therefore be RADIOACTIVE always check the radioactivity of D2O in a scintillation counter before using. 

Fluorescent materials are very important in medical research. Dyes such as fluorescein (21) can be attached to protein molecules, and the protein can be traced in a biological system by exciting the fluorescein and looking for its emissions. The use of a fluorescent material allows the detection of much smaller concentrations than would otherwise be possible. Because fluorescent materials can be activated by radioactivity, they are also used in scintillation counters to measure radiation (see Box 17.2). 

Radioactivity Analysis. Samples of urine, feces, and tissues were combusted to COo and analyzed for radioactivity (5). By using this method the recovery of radioactivity from samples spiked with C was 95 dt 5%. To determine the radioactivity expired as CO2, 5-ml aliquots of the solution used to trap the CO2 were added to 15 ml of a scintillation counting solution containing 4 grams 2,5-diphenyloxazole (PPO) and 0.1 grams l,4-bis-2(5-phenyloxazolyl)-benzene (POPOP) per liter of 1 1 toluene 2-methoxyethanol. Samples were counted for radioactivity in a Nuclear Chicago Mark II liquid scintillation counter. Counting eflSciency was corrected by the internal standard technique. 

Figure 2. Thin-layer radiochromatogram of urine (100 il) from rats injected with labeled PbTx-3. TLC plates were developed in two sequential solvent systems chloroform ethyl acetate ethanol (50 25 25 80 10 10). Radioactive zones were scraped and counted in a liquid scintillation counter. Native PbTx-3 runs at 13 cm.

PMT assays were performed as described by Vannier et al. [3] by adding an equal volume of an enzyme preparation to a 0.1 M Tris-HCl buffer containing 3.36 pM of [ C]SAM (1.8 GBq mmol, 740 kBq ml", NEN), 1% (WA ) BSA and 12% sucrose, with or without 0.2% pectic acceptor. The incubation was run at 28°C for 12 h. After precipitation of the reaction product in 70% ethanol, the methylated polymers were selectively extracted with 0.5% ammonium oxalate and radioactivity was measured in a Tricarb 2250 CA Packard scintillation counter. 

Scintillation The flash of light emitted when an electron in an excited state drops to a lower energy level. Scintillation counters are designed to measure the intensity of emissions from radioactive materials. 

After each series of experiments with beams of various intensity the section plate would be removed from the cell and disassembled, with radioactive silver washed out by nitric acid. Radioactivity of the solutions obtained was measured by a multichannel spectrometric scintillation y-counter with sensitivity of up to 10 G, i. e. around 10 of atoms which, according to calculations, is 10 times lower than sensitivity of ZnO sensor 10 G or 10 of Ag atoms respectively [28]. This difference in sensitivity lead to great inconveniences when exposing of targets was used in above methods. Only a few seconds were sufficient to expose the sensor compared to several hours of exposure of the scintillation counter in order to let it accumulate the overall radioactivity. It is quite evident that due to insufficient stability during a long period of exposure time an error piled up. 

Mnk assay (using S6peptide as substrate) Each reaction contains 20 1 of immunoprecipitated or purified recombinant Mnk, as described previously, and S6 peptide (KEAKEKRQEQIAKKRRLSSLRASTSKSESSQK, final concentration = 200 pM) in kinase buffer. To initiate the reaction, 6 p of the following mix is added 5 pi 5x kinase buffer, 0.25 pi 10 mM ATP, 1 pCi [7 32P]ATP, and H20. Reactions are carried out in an orbital shaker at 30° and 900 rpm, for example, for 20 min (Mnkl) or for 5 min (Mnk2) and stopped by spotting 20 pi of the reaction mixture onto P81 paper. The filters are washed in 1% orthophosphoric acid three times. The radioactivity is determined by using a liquid scintillation counter. 

The radioactivity in each fraction is measured by Cerenkhov counting in a LS650 Multipurpose scintillation counter (Beckman) to determine the distribution of 32P-labeled mRNA throughout the gradient. 

Radioactivity measurement The radioactivities of lead isotopes and their decay products were measured with TRICARB 3380 liquid scintillation counter (Packard Inc.). The radioisotopes concerned, and their decay charateristies are shown in Figure 2. In the case of the direct method, the absolute radioactivity can be obtained by the integral... 

C-labelled cholesterol was used to test the recovery of 5-100 pg of faecal sterols from seawater (labelled coprostanol not being available). The radioactivity of the samples and eluates was measured by a two-channel liquid scintillation counter. Percentage recovery was calculated on the basis of the amount of labeled material recovered in the acetone eluant. The results indicate that column extraction efficiency is not adversely affected by the salinity of the water samples, i.e., in the range 95-97%. 

Capsules were equilibrated with a tracer solution overnight. A capsule pellet (0.2-0.5 ml) was then placed in 5 ml test buffer (PBS or RPMI-1640 medium, Gib-co/BRL, New York, NY) on a shaker and a 0.2-ml aliquot was immediately sampled by a screen-protected pipette with further samples being taken over the next 700 s. The tracer quantity was assayed using the methods described below. A final sample was taken after the capsules has been in contact with the buffer for several hours (equilibrated tracer quantity) and the increment to the tracer concentration at each time was calculated. From the progress of tracer to equilibrium on a semilog plot a slope denoted as the zero -order rate flux constant was obtained and has been used as a measure of capsule permeability. [3H] -Glucose (580 daltons),insulin (6.2 kDa), and ovalbumin (45 kDa) have been used as tracers. Radioactivity was measured by means of a Packard 2000CA Liquid Scintillation Counter (Packard Instruments,... 

Excitation of sample by bombardment with electrons, radioactive particles or white X-rays. Dispersive crystal analysers dispersing radiation at angles dependent upon energy (wavelength), detection of radiation with gas ionization or scintillation counters. Non-dispersive semiconductor detectors used in conjunction with multichannel pulse height analysers. Electron beam excitation together with scanning electron microscopes. 

Plasma levels of dobutamine hydrochloride are determined by reaction of the drug with 3H-methyl-S-adenosylmethionine in the presence of catechol O-methy1-transferase. The radioactivity of the labeled methyl derivative is determined by a liquid scintillation counter using an external standard. The final recovery of added dobutamine as 3H-CH3-dobutamine is 24.9 1.3% in the range of 2 to 170 ng/ml (4). When 14C-dobutamine is administered the samples are counted by a double isotope method. 

Theory Generally, a radioimmunoassay makes use of a radioactive hapten and subsequently the percent of radioactivity bound to the antibody is measured. The radioactivity is determined by the help of a Geiger-Miiller Counter or Geiger-Counter or G-M Tube and sometime by a Scintillation Counter. 

The contents of the scintillation vial are mixed thoroughly, and the radioactivity is measured in a Liquid Scintillation Counter for 10 minutes,... 

The radioactivity in the supemate and that in the precipitate are separately counted in a scintillation counter. 

Both the organic and water layers from the radioactive insecticides were counted in a liquid scintillation counter (Isocap/300, Searle). The results are expressed as nanomoles or micrograms equivalent of the substrate per mg protein. 

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