Standardization activation analysis

The concentration of Mn in steel can be determined by a neutron activation analysis using the method of external standards. A 1.000-g sample of an unknown steel sample and a 0.950-g sample of a standard steel known to contain 0.463% w/w Mn, are irradiated with neutrons in a nuclear reactor for 10 h. After a 40-min cooling period, the activities for gamma-ray emission were found to be 2542 cpm (counts per minute) for the unknown and 1984 cpm for the standard. What is the %w/w Mn in the unknown steel sample ... 

This feasibility study shows that determination of pellet wt by fast neutron oxygen activation analysis can be used for quality assurance inspection of M34 primers. Either direct oxygen analysis, where a comparison standard (such as lucite) is used, or a ratio method, utilizing the Cu in the cup-anvil combination as an internal standard, can be applied. In general, the uniformity of production primers is quite satisfactory, as is usually the case where production procedures are standardized. It seems likely that the light pellet is one which has been improperly manufd and will probably be well below specifications in pellet wt. Production experience with such primers indicates that only one in 3x10s primers is expected to show low pellet wt therefore, one would not expect to find a reject in a small sampling. Nevertheless, detection and rejection of this one bad unit is critical for the prevention of weapon malfunctions and possible injuries to personnel... 

Byrne AR 1993) Review of neutron activation analysis in the standardization and study of ref erence materials including its application to radionuclide reference materials. Fresenius J Anal Chem 345 144-151. 

Tu Shu-Db, Lieser KH (1984) Homogeneity test of Chinese biological standard reference materials by means of instrumental neutron activation analysis, f Radioanal Nucl Chem Articles 84 301-306. 

Byrne AR, Deemelj M, Kosta L, and Tusek-Znidaric M (1984) Radiochemical neutron activation analysis in standardization of trace elements in biological reference materials at the nanogram level. Mikrochim Acta [Wien] 1 119-126. 

Delfanti R, Di Casa M, Gallorini M, and Orvini E (1984) Five years activity in determining trace elements for the certification of standard reference materials by neutron activation analysis. Mikrochim Acta [Wien] L239-250. 

Activation analysis, the application of radiotracers and other radiochemical methods in innovative trace analysis are indispensable, first of all in the preparation of standard reference samples. 

The average concentration and standard deviation of the Pacific Ocean waters ( xg/l) were 2.00 0.09 by neutron activation analysis, and 1.86 0.12 by atomic absorption spectrometry. For the Adriatic water the corresponding values were about 1.7 xg/l. The difference between the values for the same seawater is within the range to be expected from the standard deviations observed. 

Holzbecker and Ryan [825] determined these elements in seawater by neutron activation analysis after coprecipitation with lead phosphate. Lead phosphate gives no intense activities on irradiation, so it is a suitable matrix for trace metal determinations by neutron activation analysis. Precipitation of lead phosphate also brings down quantitatively the insoluble phosphates of silver (I), cadmium (II), chromium (III), copper (II), manganese (II), thorium (IV), uranium (VI), and zirconium (IV). Detection limits for each of these are given, and thorium and uranium determinations are described in detail. Gamma activity from 204Pb makes a useful internal standard to correct for geometry differences between samples, which for the lowest detection limits are counted close to the detector. 

Methods were described for diminishing the systematic errors in Pb activation analysis, stemming from the variable isotopic composition of Pb. Results with ICP-AES and ICP-MS were taken as standards for comparison106. 

In neutron activation analysis, the sample in a suitable container, often a pure polyethylene tube, is bombarded with slow neutrons for a fixed time together with standards. Transmutations convert analyte elements into radioactive elements, which are either different elements or isotopes of the original analyte. 

In the first step, we were able to separate this penta derivative by preparative H.P.L.C. and we subsequently treated it with an excess of propyleneimine in order to reach the required hexasubstituted compound. Under such conditions, we succeeded in preparing a N3P3(MeAz)g real sample (free of chlorine, as demonstrated by neutron activation analysis) identified by mass spectrometry (Fig. 32) and by P nmr (Fig. 33) (6 = — 36 ppm with 85 % HjPO as standard, to be compared with 8(N3P3Azg) = --37 ppm). The refractive index of this sample, n = 1.4825, appeared to be significantly far from Ratz s value. 

Some of the methods commonly used for the determination of thorium in biological materials are given in Table 6-1. The colorimetric methods are not capable of isotope-specific determination of thorium isotopes. Alpha spectrometric and neutron activation analysis are useful in the quantification of isotope-specific thorium and thorium-232, respectively, and have better sensitivities than colorimetric methods. Alpha spectrometry is the commonly used isotope-specific analysis for the determination of thorium-232 and the thorium-230 derived from the decay of uranium-238 (Wrenn et al. 1981). Standard reference materials (SRMs) containing thorium in human liver (SRM-4352) and human lung (SRM-4351) necessary for the determination of absolute recovery in a given sample are available from the National Institute of Standards and Technology (Inn 1987). 

Cadmium in acidified aqueous solution may be analyzed at trace levels by various instrumental techniques such as flame and furnace atomic absorption, and ICP emission spectrophotometry. Cadmium in solid matrices is extracted into aqueous phase by digestion with nitric acid prior to analysis. A much lower detection level may be obtained by ICP-mass spectrometry. Other instrumental techniques to analyze this metal include neutron activation analysis and anodic stripping voltammetry. Cadmium also may be measured in aqueous matrices by colorimetry. Cadmium ions react with dithizone to form a pink-red color that can be extracted with chloroform. The absorbance of the solution is measured by a spectrophotometer and the concentration is determined from a standard calibration curve (APHA, AWWA and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). The metal in the solid phase may be determined nondestructively by x-ray fluorescence or diffraction techniques. 

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. 

NAA NAAQS NBO NCP Neutron activation analysis National ambient air quality standards Non-bridging oxygen Non-carbonate portion... 

Several preparations were subjected to standard release analysis in an aqueous medium (14). The release data are shown in Figure 3. These data suggest that the lignin sulfonate 2,4-D-based preparations have the capacity for releasing herbicide activity over a prolonged time period. 

Because of the very important role of impurities in determining semiconductor properties, it is desirable to know their concentrations, at least of the electrically active ones. Of course, the techniques we have discussed in this chapter never make a positive identification of a particular impurity without confirmation by one of the established analytical techniques, such as spark-source mass spectroscopy (SSMS) or secondary-ion mass spectroscopy (SIMS). Once such confirmation is established, however, then a particular technique can be considered as somewhat of a secondary standard for analysis of the impurity that has been confirmed. It must be remembered here that an analytical method such as SSMS will see the total amount of the impurity in question, no matter what the form in the lattice, whereas an electrical technique will see only that fraction that is electrically active. 

Quantitative trace element analysis of diamond by LA-ICP-MS using different synthetic multielement carbon based standards (e.g., cellulose pellets) is discussed by Rege et al 2, whereby 13C was used for internal standardization. Concentrations of 41 elements were determined in two fibrous diamonds from Jwaneng Botswana (JWA 110 and 115) by relative sensitivity coefficients measured using the synthetic cellulose standard. The analytical data were verified by means of instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE).72... 

FT-IR has been used to determine residual catalyst support in commercial polyethylene at the level of 100 parts per million 841. The method is based on the use of the 1118 or 470 cm-1 bands to determine the quantity of silica support dispersed in the polymer. The band at 2020 cm-1 was used as an internal standard for the amount of polyethylene. Neutron activation analysis was used to calibrate the weight percent of silica present in each polymer sample. 

---