Radioactivity Standard Methods

Appendix A2 Standard Methods, part 7000—Radioactivity (Standard Methods 2005) 

Gross Alpha and Gross Beta Radioactivity (Total, Suspended, and Dissolved) 

---

Materials that demonstrate unusual reactivity with water are identified as W, and materials that possess oxidizing properties shall be identified by the letters OX. Other special hazard symbols may be used to identify radioactive hazards, corrosive hazards, substances that are toxic to fish, and so on. The use of this system provides a standard method of identifying the relative degree of hazard that is contained in various tanks, vessels, and pipelines. 

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). 

A standard method for leach-testing immobilized radioactive waste solids and for reporting results has been proposed(10). 

Hydrolyze an aliquot in O.IMHQ for 20 h at ST C and calibrate by strong cation exchange HPLC on a Whatman Partisil 10 SCX column or by column chromatography on Sephasorb, uang appropriate optical or radioactive standards. Detailed descriptions of these methods can be found elsewhere (6,7). 

Among various techniques used for radioactivity standardization, the 4ti P-y coincidence counting method is undoubtedly the most important technique, and most radionuclides can be standardized by this technique or its extended techniques. Actually, most national standardizing laboratories in the world employ this method for the establishment of the national standards of various kinds of radionuclides. 

The index of quenching in this method is obtained from an areal ratio or a centre of gravity with respect to a 3-ray spectrum. The radioactivity is determined through a similar quenching correction curve to that of the external standard method. 

An understanding of the competitive binding assay can provide a dear picture of the alterations that can pose a risk for cardiovascular disease. In the study depicted in Figure 6.30, apo E preparations isolated from the plasma of one normal subject and two patients were subjected to competitive binding assays. In beginning the study, the researchers used standard methods for connecting atoms of radioactive iodine (iodine-125) to apolipoprotein E. 

For the analysis of the new surface after every removal one may use all the surface techniques already mentioned in Sect. 4.3.1 as long as their information depth does not exceed the thickness of the layer removed Auger and ESCA-spectroscopy, secondary-ion mass spectrometry (SIMS), backscattering, ion-induced X-ray and nuclear reaction analysis. In addition, one may investigate the content of the element of interest in the removed layer. Because of the low absolute concentration of implanted ions most of the standard methods of analysis fail. The best results come from implantations of radioactive elements followed by measuring the radioactivity of the dissolved removed layer. 

Properly, radionuclide concentrations are reported in units consistent with the method used for their determination. A radioanalytical technique such as liquid scintillation or alpha spectrometry yields a result expressible in terms of radioactivity. A mass-based analytical technique, such as laser phosphorimetric determination of U(aq) yields mass-based concentrations such as micromoles per liter. Detection limits using radioactivity measuring methods are often many orders of magnitude lower than those possible with mass-based methods (cf. Krieger and Whittaker 1980). For example, 100 pCi/L of Rn, a concentration easily determined by liquid scintillation, equals 2.93 x 10" M, or approximately 1.76 x 10 atoms/L. At standard temperature and pressure, this amount of radon has a minuscule partial pressure of 6.6 x 10" bar, assuming ideal gas behavior. 

Total concentrations of trace elements were determined by neutron activation analyses and atomic absorption. Radium concentrations were determined by the emanation method and by the germanium-lithium counting of natural radioactivity, corrected by reference to a National Bureau of Standards (NBS) uranium ore. Chemical analyses were performed by standard methods. 

If methods are used in which the overall recovery is 70% or above, and if the possibility of accidental but undetected very large losses is reduced by using a minimum of steps and transfer operations, or by automation, it is questionable whether in practice the precision will be greatly increased by current techniques of using internal radioactive standards. In the case of many urinaiy steroids, conjugated internal standards would be required for full control of the procedure and are not yet generally available. Finally the technique itself is not error-free, even in the absence of isotope effects, and the usual techniques employed so far often involve very small volumes of volatile solvents in which transfer errors can be large unless very superior manual technique is used. 

Salt Solutions. The radioactive isotopes used were Na, Br and S, which were obtained from Oak Ridge National Laboratory with permission of the Atomic Energy Commission. They were obtained in the form of simple acids or salts and were converted to the desired form by standard methods, such as the use of ion-exchange columns and titration. The salts Na Br, NaaS04 and Na2 S04 were prepared. 

The development of various simple methods, including internal standard methods involving the use of labelled and radioactive element standards. 

De Vooys (1979) is also of the opinion that the generally accepted estimates of primary productivity in the world ocean are too low, mainly as a result of shortcomings of the radiocarbon method. He proposes an overall correction of the existing values by an increase of 40% based on loss of radioactivity on storing plankton filters in a vacuum desiccator (20%), as is common practice in the standard method of Strickland and Parsons, (1972) and on account of loss of extracellular excretion products (20%). In his opinion the corrected estimate of Platt and Subba Rao (1975 44 X 10 t C yr" ) is the best approximation of primary production in oceans and seas. 

For the COX-1 and COX-2 assay, the diluted solution of the test compound is incubated with COX-1 or COX-2 according to the standard method and then the enzyme reaction is initiated by the addition of [l- C]-arachidonic acid. From the incubation mediate, prostaglandin E2 and prostaglandin D2 (PED2) are extracted to measure radioactivity. Indomethacin is used as a positive control. For the 5-LOX assay, the inhibitory activity of the test compound is evaluated. The test compound is incubated with 5-LOX (46pg of protein) at 24°C for lOmin, and then the enzyme reaction is initiated by the addition of [l- C]-arachidonic acid (50nCi). After 5 min, 4-M formic acid is added to terminate the enzyme reaction. Indomethacin is used as a positive control. 

Advantages and Limitations of IIDA. The main advantage of this method is that one can determine the quantity of a specific radioactive component of a sample without comparing it with a known radioactive standard. The method also avoids preparing standards with the same matrix as the sample in order to assure equivalent... 

Journals such as Radio chemistry. Radioactivity and Radiochemistry, and the Journal of Radioanalytical and Nuclear Chemistry currently are vehicles for publishing radioanalytical chemistry methods. Groups such as the American Society for Testing and Materials (ASTM) and the American Public Health Association (APHA) publish standard methods for radiochemistry (see Section 6.5), among other topics. 

---