Radiometric analysis

Radiometric analysis using a plastic scintillator connected to coincidence and anticoincidence circuits (e.g. a Picobeta counter) can be used to detect "Tc. The detection limit is estimated to be about 10 mBq. A slightly better detection limit (1-5 mBq) is reported for a gas flow counter with an anticoincidence shield [8],... 

Hedges, R.E.M. and McClennan, M. (1976). On the cation exchange capacity of fired clays and its effect on the chemical and radiometric analysis of pottery. Archaeometry 18 203-207. 

In this type of radiometric analysis, a tracer quantity of a radioactive isotope is added to the analyte, which is then partly extracted using a specific extractant. Since the extractant may be considered as reacting totally with the analyte, the ratio of radioactivity in both phases provides the concentration of analyte in the sample. This method, first developed by Stary [2], has proved to be useful in several systems. 

In the product, there should be a ladder-type blocks linked by segments composed of p-cresyl methacrylate units. This type of structure was confirmed by IR and NMR spectrometry. However, by preparation of such copolymers with labeled end-groups (using radioactive AIBN), and by fractionating and radiometric analysis, it was shown that copolymers obtained are slightly branched. There is slightly more branch points than in the case of copolymers with styrene. It could be an effect of chain transfer reaction. 

Using labeled initiator and radiometric analysis, the number of initiator fragments from the number of end-groups, R, can be evaluated and the number of crosslinking points can be calculated. The number of unreacted double bonds can be found by the bromometric method. On the basis of such analysis, we can find the percentage of units in the multimonomer which had reacted according to template mechanism. The results of the calculations for two examined systems are presented in Tables 5.3 and 5.4... 

All methods of radiometric analysis involve, of course, the use. of various radiation detection devices, The devices available for measuring radioactivity will vary with the types of radiations emitted by the radioisotope and the kinds of radioactive material. Ionization chambers are used for gases Geiger-Miiller and proportional counters for solids liquid scintillation counters for liquids and solutions and solid crystal or semi-conductor detector scintillation counters for liquids and solids emitting high-energy radiations. Each device can be adopted to detect and measure radioactive material in another state, e.g., solids can be assayed in an ionization chamber. The radiations interact with the detector to produce a signal,... 

R. Garcia and B. Kahn, Total Dissolution of Environmental and Biological Samples by Closed-Vessel Microwave Digestion for Radiometric Analysis, J. Radioanalytical and Nuclear Chemistry 250, 85-91 (2001). 

Methionine Sulfoxide Adsorption Check. S35-labeled methionine sulfoxide was prepared by oxidizing methionine-S35 with peroxide (6). Five microliters (ca. 20,000 counts per minute per microliter) of an aqueous solution of the sulfoxide was injected into each of 20 cockroaches. The first 10 were immediately immersed in hot 80% ethanol, and the remainder in hot 5% trichloroacetic acid to be homogenized and extracted. The extraction procedures were similar to those described above, except that precautions to prevent oxidation were not taken and the supernatant liquids, except for the acidified ethanol and ether washes, were not combined but were collected separately in 100-ml. volumetric flasks. The protein residues were hydrolyzed in 6N HC1 and, like the other fractions, were then diluted to 100 ml. with water for radiometric analysis. 

Radiometric analysis is also based on the use of radiotracers. However, in contrast to isotope dilution analysis, stoichiometric relations are applied in radiometric methods. The substance to be determined is brought into contact with another substance labelled with a radionuclide or containing a radionuclide. Reaction between these two substances yields a radioactive product that either can be separated and measured or can be measured continuously in the course of the reaction. The activity is proportional to the amount of substance to be determined. 

Miyairi, S. and J. Fishman (1985). Radiometric analysis of oxidative reactions in aromatization by placental microsomes. Presence of differential isotope effects. J. Biol. Chem. 260, 320-325. 

Mercury (Hg) occurs in nature as a mixture of seven stable isotopes the average atomic mass of the blend is 200.6. The atomic masses and natural abundances of the isotopes are 196.0 (0.15 %), 198.0 (10.1 %), 199.0 (17 %), 200.0 (23.1 %), 201.0 (13.2 %), 202.0 (29.65 %) and 204.0 (6.8 %). Two radioactive isotopes, and ° Hg, have been widely used in toxicological studies, radiometric analysis, and also in checks of yield of analytical procedures. The fact that mercury is an isotope mixture may be of importance in analytical work using mass spectrometry, since there are no reference samples with well-defined isotope composition. 

The term radiometric analysis is often used in a broad sense to include all methods of determination of concentrations using radioactive tracers. In a more restricted sense it refers to a specific analytical method which is based on a two-phase titration in the presence of a radioactive isotope. The endpoint of the titration is indicated by the disappearance of the radioisotope from one of the phases. Figure 9.4 illustrates two cases, (a) the determination of Ag in a solution by titration with Nal solution containing ( y t 1.57x10 y),and (b) the determination of Fe in an aqueous solution, to which trace amounts of radioactive Fe (EC 2.73 y) has been added. In case (a) the Agl precipitate is radioactive but the solution has little radioactivity until all the Ag has been precipitated. The activity of the solution is measured by a liquid flow GM-detector (Ch. 8). In the latter case (b) a two-phase liquid-liquid analytical technique is used ( 9.2.6) the titrant contains a substance (oxine) which extracts Fe(II) from the aqueous to the chloroform phase. The radioactivity of the organic phase is followed by liquid scintillation (sampling) to determine the end point of the titration. 

Radiometric analysis is sinqjle and rapid. Nevertheless, it is rarely used in analytical routine work, as a large number of multiple-element "instrumental techniques are readily available (though the instruments usually are more expensive). Its most extensive use is for calibration of other techniques, and in analytical comparative techniques (e.g. environmental... 

Garcia, R. and Kahn, B. 2001. Total dissolution of environmental and biological samples for radiometric analysis by closed-vessel microwave digestion. J Radiological Nucl Chem 250, 85-91. 

The reactor water parameters, such as conductivity, pH and chloride ion concentration, were monitored periodically, and radiometric analysis of the water was also carried out (Table 6.3). The conductivity was determined directly (but intermittently) by the probe in the deionizing circuit. Conductivity was maintained at <2.0 j.S/cm.The pH was always in the range 5.5-6.5 and the chloride ion concentration was <0.2 ppm. When the conductivity came close to 2.0 j.S/cm or the chloride content came close to 0.2 ppm, the deionization resins were regenerated. The water specimens for radiological analysis were collected once a week after the reactor was switched off. Gamma spectroscopy was carried out to determine the nuclides Co, Co, Cr, Cs,... 

Radiometric analysis, or radiometry, is a method of analysis in which a radioactive tracer is employed as an indicator or a reagent. Among them, the most important one is the isotope dilution analysis discussed separately below. Isotope dilution analysis is also used to determine the amount of radioactive elements or compounds (inverse isotope dilution analysis). 

The total taxane (TTAX) concentration, a sum of the concentrations for CT-2103, TXL, and TXL-metabohtes was determined from scintillation counting of the plasma or tissue sample homogenates. Extractable taxanes, including TXL and organically extractable TXL metabolites, were determined by scintillation counting of ethyl acetate extractions of the plasma, tumour, liver, and spleen samples. Plasma and tissue TXL concentrations were also determined by HPLC/radiometric analysis of the extracts. Metabolites were identified by HPLC followed by mass spectrometry on a Quattro It (Micromass, Manchester, UK) triple quadrupole mass spectrometer fitted with an electrospray orthogonal Z spray ion interface operating in the positive ion mode. ... 

Radiometric analysis. Physical mixtures were made up by weight from 100 mesh polymer flour ... 

Technetium-99 concentrations were above the analjdical limit of detection (i.e. values positively detected) at all three sites. At Carlingford Lough (North-west Irish Sea), all the trend data, with the exception of caesium-137 (in 2012) and americium-241 (1998 - 2007, 2009 - 2010 and 2012-2013) were positively detected Further north along the coastline at Kilkeel, all caesium-137 data were positively detected (except in 2003 and 2005), whilst all americium-241 data were below the limit of detection (by radiometric analysis). Towards the border of the North Atlantic Ocean at Ballycastle, all caesium-137 data were... 

The Search for Superheavy Elements in Nature.— In view of the low concentrations expected, the sensitivity provided by radiometric analysis is clearly required, and it would be most helpful if these elements were to concentrate in particular materials. Vdovenko and Sobotovich have indicated, on... 

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