Scintillators atomic spectroscopy

Secondary isotope effects are small. In fact, most of the secondary deuterium KIEs that have been reported are less than 20% and many of them are only a few per cent. In spite of the small size, the same techniques that are used for other kinetic measurements are usually satisfactory for measuring these KIEs. Both competitive methods where both isotopic compounds are present in the same reaction mixture (Westaway and Ali, 1979) and absolute rate measurements, i.e. the separate determination of the rate constant for the single isotopic species (Fang and Westaway, 1991), are employed (Parkin, 1991). Most competitive methods (Melander and Saunders, 1980e) utilize isotope ratio measurements based on mass spectrometry (Shine et al., 1984) or radioactivity measurements by liquid scintillation (Ando et al., 1984 Axelsson et al., 1991). However, some special methods, which are particularly useful for the accurate determination of secondary KIEs, have been developed. These newer methods, which are based on polarimetry, nmr spectroscopy, chromatographic isotopic separation and liquid scintillation, respectively, are described in this section. The accurate measurement of small heavy-atom KIEs is discussed in a recent review by Paneth (1992). 

Two further analytical methods are based on the formation of metal complexes. Reaction of dopamine with KzCrjOy gives a Cr complex which can be assayed by atomic absorption spectroscopy, carbon rod absorption spectroscopy or, if Kf CrjO has been used, by liquid scintillation spectroscopy. Since the complex still gives a reaction with fluorescamine, the side-chain is thought not to be involved in the formation of the complex. Methamphetamine hydrochloride can be precipitated as a Bi complex. Determination of the amount of Bi remaining in solution by atomic absorption spectroscopy provides an indirect method of assay for the amphetamine. ... 

GPC (total radioactive strontium) = beta gas proportional counter Bq = Becquerel dpm = disintegrations per minute EDTA = ethylenediamine tetraacetic acid GFAAS (total strontium) = graphite furnace atomic absorption spectroscopy ICP-AES (total strontium) = inductively coupled plasma atomic emission spectroscopy ICP-MS (isotopic strontium composition) = inductively coupled plasma-mass spectrometry LSC (isotopic quanitification of 89Srand 90Sr) = liquid scintillation counting pCi = pico curies (10-12 curies) PIXE (total strontium) = proton induced x-ray emission TMAH = tetramethylammonium hydroxide TNA (total strontium) = thermal neutron activation and radiometric measurement TRXF (total strontium) = total-reflection x-ray fluorescence... 

All of the details involved in obtaining precision results from y-ray spectroscopy with Ge detectors apply to Nal(Tl). If fact, the methods were developed with Nal(Tl) and later applied to Ge. Nal(Tl) is superior to Ge in effective atomic number (total energy absorption), operation at room temperature, and size (up to 25 cm linear dimensions for the scintillator). But the vastly superior resolution of Ge dominates aU other characteristics for most users. At about 1,000 keV, the energy resolution of a Ge detector is about 1.5 keV, and that of Nal(Tl) is about 60 keV O Fig. 48.15. Whereas Ge spectra can be analyzed in terms of individual peaks and their areas, Nal(Tl) spectra are usually analyzed in terms of the overall, somewhat indistinct pattern each nuclide produces under the conditions of the measurement. When conditions change and effects such as summing and pileup change, the patterns change. 

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