Peak activation analysis

Selected ion monitoring can be used for the determination of the relative amount of each component of a mixture, introduced into the mass spectrometer by the direct inlet probe However, such a determination requires reference mixtures of known composition for calibration. In the present experiment, since the monochloro pentaziridino derivative had not yet been isolated in the pure form, it was necessary to determine its concentration, by an auxiliary method, in a sample which could then be utilized as a reference mixture for further experiments. In order to do this we titrated chlorine in the toxic sample of MYKO 63 (B) by the classical method. The results indicated that the amount of N3P3AZJCI was between 0.5-1.5 %. The large statistical error is due to the low chlorine content in the sample examined. Thus, we used the remarkable possibilities provided by neutron activation analysis when the impurity to be quantified is a chlorinated moiety. It is well-known indeed that the C1 -f 2n peak is amongst the most easily detectable by neutron... 

All impactor and filter samples were analyzed for up to 45 elements by instrumental neutron activation analysis (INAA) as described by Heft ( ). Samples were irradiated simultaneously with standard flux monitors in the 3-MW Livermore pool reactor. The x-ray spectra of the radioactive species were taken with large-volume, high-resolution Ge(Li) spectrometer systems. The spectral data were transferred to a GDC 7600 computer and analyzed with the GAMANAL code (1 ), which incorporates a background-smoothing routine and fits the peaks with Gaussian and exponential functions. 

Stefanov and Daieva [102] determined micro amounts of iridium in soil by neutron activation analysis. The soil is activated for 30 hours in a neutron flux of 5 x 1012 neutrons/cm/s, then left for 2-3 days to decay, and then iridium was determined from the 317 keV peak of 123iridium. Down to 30 ng of iridium in soil could be determined. 

Ralston, H. R., and G. E. Wilcox A Computer Method of Peak Area Determination from Ge(Li) Gamma Spectra. The 1968 International Conference Modem Trends in Activation Analysis, Gaithersburg, Maryland, October 7—11, 1968, Paper 37. 

Atomic absorption spectroscopy, neutron activation analysis, I CP-optical emission spectroscopy Inorganic bulk and surface impurities of packings Chemical stability of packing, retention of solutes, peak tailing... 

Activation analysis may be qualitative or quantitative. In a qualitative measurement, only identification of the element is involved. This is accomplished, as shown in Sec. 12.7.3, from the energies and intensities of the peaks of the spectrum. In a quantitative measurement, on the other hand, in addition to identification, the amount of element in the sample is also determined. To illustrate how the mass is determined and what the errors and sensitivity of the method are, consider the energy spectrum of Fig. 15.1 as an example. 

Events that initiate misfolding of the native PrP polypeptide remain mostly unknown however, it has been shown in a model system of neuroblastoma cell cultures that normal PrP is precursor to PrP (Borchelt et al., 1990). These studies employed a 2-h pulse of [ S]-methionine to label the newly synthesized PrP. Kinetic analysis of [ S]-radioactivity in purified protein showed that labeling peaked immediately in the PrP pool and rapidly declined to less than 90% of peak activity within 14-22 h, whereas radioactivity was still increasing after 46 h in the 1 - = pool. Given a pulse duration of only 2 h, followed by chase, it is reasonable to assume labeled PrF is the direct precursor of labeled PrP Furthermore, studies with recombinant PrP polypeptides show that a-helix-rich polypeptides, which are characteristic of the native PrP configuration, can be... 

The /7-polarized IR transmission spectra (cp = 75°) for PSG layers with different phosphorns content are shown in Fig. 6.8 [36]. In addition to the Si02 bands, an intense peak at 1325 cm from P=0 bonds was observed [33-38]. The ratio of the absorbance at 1325 cm to that at 1080 or 1250 cm depends linearly on the phosphorus concentration determined by methods such as chemical or neutron activation analysis. The same dependence is observed in spectra of borosilicate glass for the ratio of the absorbance at 1350 cm to that at 1080 cm this is used for determination of the boron concentration in borosilicate glass films [38-40]. This determination of the absolute concentration of phosphorus in PSG films by IR spectra was developed in [41]. 

In PGAA, one is interested in the correlation of the characteristic spectral peak areas and the masses of the emitting components. The calculation here is simpler, for many reasons, than in neutron activation analysis (NAA) ... 

Blood Neutron activation analysis was used to determine the level of uranium in samples of blood, urine, and hair of exposed people (woikers in uranium production facilities in Slovenia) and unexposed population (Byrne and Benedik 1991). Blood samples were collected by venipuncture from the arm. The samples were freeze-dried and powdered and well mixed before encapsulation in polythene vials that were heat-sealed. The samples were irradiated with a 4 10 n cm s neutron flux for up to 30 min and rapidly ashed with 50 mg of uranium that served as a carrier. The uranium was then extracted with TBP in toluene and after cleaning the organic phase by acid washing the samples were counted with a HPGe gamma detector for 20 min. The 74.7 keV peak formed by neutron irradiation and the 185.7 keV peak (from the... 

In most branches of analytical science, methods are checked and monitored using reference materials. When purchased, these are accompanied by a certificate that specifies the concentration, with an associated uncertainty, for a number of chemical entities. These will have been analysed by at least two different analytical methods and provide benchmarks against which methods and laboratories can be assessed. Indeed, gamma-ray spectrometrists plying their trade in the service of neutron activation analysis would utilize such reference materials routinely. The corollary for testing gamma-ray spectra would be to have available reference spectra that contained peaks at known positions containing known numbers of counts. It would be unrealistic, perhaps, to expect one spectrum to test aU aspects of spectrum analysis but a small number of... 

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