Radioactive counters

These two equipments shall now be discussed briefly as follows  

In usual practice, two types of radioactive counters are mainly employed depending on the type of radioactive substance used, namely  

These are used invariably for the gamma-energy emitting isotopes, for instance 125I-the more common iodine-isotope. 

These are mostly used for counting beta-energy-emitting isotopes, such as tritium 3H and 14C-(Carbon-14) isotopes. 

The methodology of the radioimmunoassay have been studied extensively and outlined in a sequential manner as follows  

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C22-0051. A radioactive nuclide of mass number 94 has been prepared by neutron bombardment. If 4.7 pg of this nuclide registers 20 counts per minute on a radioactivity counter, what is the half-life of this nuclide ... 

C22-0123. A radioactivity counter gave a reading of 350 Min for a 12.5-mg sample of cobalt(II) chloride... 

These techniques are especially useful for studies of the adsorption of reactants, intermediates and products of electrode reactions. The simplest case corresponds to adsorption that is so strong that the electrode can be removed from the solution, rinsed and its activity measured without interference from desorption. When this procedure is impossible, the activity of the adsorbate can be measured by the electrode lowering method . The radioactive counter is placed under the bottom of the cell, which is made of a plastic foil. The electrode can be located at large distances from the bottom or can be placed so close to the bottom that only a thin layer of solution remains beneath it. The radioactivity values at the two electrode positions permit determination of the adsorbate activity. This procedure can be repeated many times, thus supplying data on the kinetics of the adsorption process. 

In essence this measures vC meter or radioactivity counter also... 

Protactinium is separated by solvent extraction and anion exchange processes by using sulfate solutions. After chemical separation, the protactinium salts are ignited to a pentoxide, Pa205, which may be converted into an arsenazo(III) complex. The absorbance of the solution is measured at 630 nm with a spectrophotometer. Protactinium-231 is an alpha emitter and also forms photons at 300 KeV, which can be measured by various radioactive counters and spectrophotometric techniques. Protactinium also can be measured by neutron activation analysis. 

Gross alpha and gross beta activity can be determined by various radioactive counters, such as internal proportional, alpha scintillation, and Geiger counters. Radium in water can be measured by co-precipitating with barium sulfate followed by counting alpha particles. Radium-226 can be measured from alpha counting of radon-222. Various methods are well documented (APHA, AWWA, and WEF 1998. Standard Methods for the Examination of Water and Wastewater, 20 ed. Washington DC American Public Health Association). 

Yin, H., Greenberg, G. E., and Fischer, V. (2000). Application of Wallac Microbeta radioactivity counter and Wallac Scintiplate in metabolite profiling and identification studies. Application note. PerkinElmer Life Sciences, accessed at http //www.perkinelmer.com. 

A radioactivity counter can tell if your skin is contaminated with uranium, because uranium is radioactive. If you inhale large amounts of uranium, it may be possible to measure the amount of radioactivity in your body with special radiation measurement instruments. See Chapters 2 and 6 for more information. 

Altshuler, B. and Pasternack, B. 1963. Statistical measures of the lower limit of detection of a radioactivity counter. Health Phys 9, 293-298. 

Lower Limit of Detection of a Radioactivity Counter. Health... 

Iodine-129 has little practical use, but may be used to check some radioactivity counters in diagnostic testing laboratories. 

Instruments or articles with low activities (e.g., clocks, sun lamps, photoelectric cells, fire alarm sensors, radioactivity counters, x-ray tubes). 

The standard technique to check the radiochemical purity of a labeled compound is thin layer chromatography/instant thin layer chromatography (TLC/ITLC) combined with a radioactivity counter. This method is quick and easy to perform. Different isomeric forms of a radiopharmaceutical may not be determined. A more sophisticated method for quality control is high performance liquid chromatography (HPLC) combined with a radioactivity detector. Radiochemical purity as well as isomeric forms and small modifications due to instability, radiolysis, etc., may be determined. To achieve an accurate determination of non-chelated radiometal, a mM solution of DTPA (pH 4-5) has to be added to the HPLC sample to ensure a complexation of the free metal. If DTPA is not added, unchelated metal might bind and stick to the HPLC column and thus indicate a too high radiochemical purity (Smith-Jones etal. 1998). 

Isotope labeling— Although radioactive isotope labeling has been used for 2D-electrophoresis, it is not a popular method because of the exceptional safety requirements. There is a need for a separate laboratory room, advanced equipment (radioactivity counters), and conditions designed for... 

Iodine-129 Reactor Checking of radioactivity counters in in-vitro diagnostic testing... 

An in vivo test for the diagnosis of thyroid disorders which consists of giving radioactive iodine to the patient and measuring its uptake by the thyroid gland, by means of a radioactive counter placed over the gland. Uptakes are usually measured after 4 or 24 hours. High uptakes occur in hyperthyroidism whereas low uptakes are found in hypothyroidism. 

Capillary method Unsteady out of finite cell Small Easy Average Concentration vs. time usually requires radioactive counter Good, but commonly used only with radioactive tracers... 

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