Impurity concentration measurements emission spectroscopy

The sodium hydroxide is titrated with HCl. In a thermometric titration (92), the sibcate solution is treated first with hydrochloric acid to measure Na20 and then with hydrofluoric acid to determine precipitated Si02. Lower sibca concentrations are measured with the sibcomolybdate colorimetric method or instmmental techniques. X-ray fluorescence, atomic absorption and plasma emission spectroscopies, ion-selective electrodes, and ion chromatography are utilized to detect principal components as weU as trace cationic and anionic impurities. Eourier transform infrared, ft-nmr, laser Raman, and x-ray... 

Transition metal dopants and impurities are probably incorporated substitutionally for Ti in BaTi03. Emission spectrographic analyses indicate that the distribution coefficients for Mn and Fe dopants are on the order of 1 to 2, i.e., the crystals are slightly enriched relative to the melt. Cr and Ni may have distribution coefficients slightly less than 1. For Co, the measured concentrations in the crystals display considerable scatter we estimate that the distribution coefficient is on the order of 4. Fe is the most prevalent transition metal impurity and is typically present at a concentration of 10-15 ppm by weight. Si, Al, Mg, and Cu are also typically present at 5-50 ppmw. Fe and Cr impurities have also been observed by EPR spectroscopy, although Cr could not be detected by emission spectroscopy, with a detection limit of 10 ppmw. 

Salt purity, density, chemical composition, and other properties. In the laboratory, high-temperature salt properties are measured by spectroscopy. Laser or other light is sent through the salt, and the transmission of the light is measured as a function of frequency. In more sophisticated systems, secondary emission lines are measured. Salt impurities that can be measured to very low concentrations include uranium, the actinides, iron, chromium, and nickel. The chemical valence state can also be measured. This is likely to be the preferred method for monitoring the concentration of impurities and the redox potential of the salt and thus the performance of the salt cleanup systems. It would be the equivalent of the instrumentation used to monitor water chemistry in an LWR. 

FBAs can also be estimated quantitatively by fluorescence spectroscopy, which is much more sensitive than the ultraviolet method but tends to be prone to error and is less convenient to use. Small quantities of impurities may lead to serious distortions of both emission and excitation spectra. Indeed, a comparison of ultraviolet absorption and fluorescence excitation spectra can yield useful information on the purity of an FBA. Different samples of an analytically pure FBA will show identical absorption and excitation spectra. Nevertheless, an on-line fluorescence spectroscopic method of analysis has been developed for the quantitative estimation of FBAs and other fluorescent additives present on a textile substrate. The procedure was demonstrated by measuring the fluorescence intensity at various excitation wavelengths of moving nylon woven fabrics treated with various concentrations of an FBA and an anionic sizing agent. It is possible to detect remarkably small differences in concentrations of the absorbed materials present [67]. 

A substantial advantage of emission Mossbauer spectroscopy in comparison with the transmission technique is that if the material to be investigated contains heavy elements, then the required dopant concentration (e.g., Co) may be 1-2 orders of magnitude lower in the emission experiment than the Fe concentration in an analogous transmission experiment. This is in connection with the intensity loss of the Mossbauer radiation due to electronic absorption, which is always self absorption in the source and regular absorption in the absorber (Vertes and Homonnay 1997). Low dopant concentration is very important in impurity Mossbauer spectroscopy, where the investigated material does not contain a Mbssbauer element thus, a conveniently measurable Mbssbauer nuclide is introduced artificially as an impurity with a potential risk of perturbing the physicochemical properties of the host phase. 

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