Selenium analysis

As with selenium analysis, HGAAS also finds a place in Te determination. Basnayake et al. amended cultures of P. fluorescens K27 with 0.1 mM tellurite and, after 92-h growth, determined that approximately 34% of added Te was present as either precipitated, elemental Te in/or on centrifuged cells the balance of added Te remained in solution.190 In this same study, GC/MS was used for determination of DMTe in the same facultative anaerobe amended with tellurate.190 Earlier, GC/MS was used to analyze the headspace of a tellurium-resistant fungus amended with tellurite.215 This last is one of the few reports of the detection of dimethyl ditelluride in microbial headspace (see below). 

Hydroboration-protonolysis, 23 648 Hydroboration reaction, 23 632-646 Hydroborofluoric acid, 4 150 Hydrobromic acid, 4 319 22 823 use in selenium analysis, 22 94... 

Selenourea inclusion compounds, 14 172 Selenous acid, 22 73t, 75t, 88-89 use in selenium analysis, 22 94 Self-accelerating decomposition... 

Sodium thiosulfate, 23 674 use in selenium analysis, 22 94-95 Sodium titanate, 25 100 Sodium toluenesulfonate... 

The Raman spectrum of the reaction product of titanocene pentasulfide and dichlorodiselane shows the presence of l,2,3-Se3Sj as the main species (sea Fig. 3). The normal coordinate treatment using a modified Urey-Bradley force field with 12 independent force constants resulted in a complete assignment of the spectrum and in a very good agreement between the observed and calculated wave numbers. The composition of the phase as determined from the HPLC data, molecular weight measurement, and selenium analysis agrees with the vibrational analysis. 

Hypophosphorus acid -m selenium analysis [SELENIUM AND SELENIUM COMPOUNDS] (Vol 21) - [PHOSPHORUS COMPOUNDS] (Vol 18)... 

Flinn and Aue [767] proposed a photometric detector for selenium analysis which enables determination of 2 10 12g selenium s 1... 

Hussein, L., Bruggeman, J. Selenium analysis of selected Egyptian foods and estimated daily intakes among a population group. Food Chem. 65, 527-532 (1999)... 

Na202 for arsenic and selenium Approximately 0.5 g of pulverized samples are mixed with 2 g of Na202 in a 30-mL zirconium crucible. The covered crucibles are placed in a 450°C oven and the temperature is raised to 600°C and maintained for 0.5 hr. The fusion is dissolved in 6M HCl. (This acid concentration is convenient for the subsequent analysis by hydride generation coupled with atomic absorption spectrophotometry (A.A.S.)). The final volume of these solutions is 100 mL. Separate aliquots with and without Nal reducing agent are taken for arsenic and selenium analysis, respectively. 

Arsenic analysis by atomic absorption selenium analysis by fluorimetry molybdenum analysis by colorimetry. 

Historically, analysis for selenium has been difficult, partly because environmental concentrations are naturally low. Indeed, selenium analysis still remains problematic for many laboratories at concentrations below 0.01 mg a relatively high concentration in many environments (Steinhoff et al., 1999). Hence, selenium has often been omitted from multi-element geochemical surveys despite its importance (Darnley et al., 1995). Analytical methods with limits of detection of <0.01 mgL include colorimetry, total reflectance-XRF, HG-AFS, gas chromatography... 

Laboratory methods. Huorimetry has been used widely for selenium analysis in environmental samples but is being superseded by more sensitive instrumental methods. Some of the instmmental methods used for arsenic speciation and analysis can also be used for selenium. In particular, HPLC and HG can separate selenium into forms suitable for detection by A AS, AFS (Ipolyi and Fodor, 2000), or ICP-AES (Adkins et al, 1995). Only Se(IV) forms the hydride, and so Se(VI) must be prereduced to Se(IV) if total selenium is to be determined. This is normally achieved using warm HCl/KBr followed by co-precipitation with La(OH)3 if necessary (Adkins et al., 1995). KI is not used, since it tends to produce some Se(0), which is not reduced by HG. La(OH)3 collects only Se(IV), so the prereduction step to include the contribution from Se(VI) is required before co-precipitation. Other methods of preconcentration include co-precipitation of Se(IV) with hydrous iron oxide or adsorption onto Amberlite IRA-743 resin (Bueno and Potin-Gautier, 2002). 

The major selenium-containing plasma protein selenoprotein P can be determined by immunological methods. The production of monoclonal antibodies to selenoprotein P has been described and used to study tlie structure and function of the protein and to quantify it. It is also possible to separate selenoprotein P from other plasma proteins by heparin affinity chromatography followed by CFAAS selenium analysis. Selenoprotein P concentration in plasma responds rapidly to supplementation and has been used in nutritional studies of Chinese populations to confirm the adequacy of intake. "... 

Tolg G (1984) Selenium-analysis in biological materials. Trace Element Analytical Chemistry in Biology and Medicine 3 95-125. 

For selenium analysis, Chlamydomonas GSHPOD subunit was excised from a slab gel in SDS-PAGE and measured fluorometrically using 2,3-di-aminonaphthalene after digestion with nitric and perchloric acids (5). 

These techniques can be used throughout an organization or in smaller pieces such as a particular chemical process. Eor example Lean Six Sigma has been used to improve a selenium analysis [6] and showed the importance of improving the digestion of the sample. 

In species-unspecific isotope dilution techniques, an isotopically enriched standard solution is added post-column, and the data evaluation is performed as described in Section 7.3.4 for CE coupling. Species-unspecific isotope dilution for HPLC coupling has been described for the determination of Cd, Cu and Zn in metallothioneins extracted from eel liver, while Fe, Cu and Zn were determined in proteins separated from human serum. This technique has also been applied to iodine determination in humic substances,as well as selenium speciation in human serum. Species-specific isotope dilution using HPLC-ICP-MS has been described for selenium analysis, the analysis of organotin species in sediments, methylmercury in fish tissue, trimethyllead in water, and chromium speciation. Overviews to this topic have been published, e.g. by Heumann and Hill. ... 

X-ray fluorescence is applicable to selenium analysis for biological and other samples, and show good correlation with neutron activation [20, 52]. The volatile nature of seleno-compounds makes them good subjects for gas chromatography. An advantage of gas chromatography is the available field units which can detect levels as low as 0.1 ppm [18]. 

McKown, D.M., Morris, J.S. Selenium Analysis methodology and applications, p. 338-344, in [D.D. Hemphill (ed.)] Trace Substances in Environmental Health - XI, Proc. Univers. Missouri s 11th Ann. Conf. Trace Substances in Environm. Health, Columbia, Univers. Missouri, 1977 Muth, O.H., et al. Science 128, 1090 (1958)... 

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