A second-derivative spectrophotometric method has been developed for the simultaneous determination of uranium and thorium using 4-(2'-thiazolylazo)resacetophenone oxime as the spectrophotometric reagent. The method allows the determination of uranium and thorium in the range 0-10.0 ppm. The relative error is less than 4%. Common anions and cations do not interfere in the determination even when present in large amounts. However, for transition metal ions, viz., Cu, Ni, Pd and Pt, the tolerance limit is less than 100 ppm.
A sensitive and selective sub-stoichiometric isotope dilution method for the determination of trace amounts of selenium is described. The method is based on the extraction of the selenium-dithizone complex with a sub-stoichiometric amount of dithizone into toluene from 7 rnol 1-1 hydrochloric acid. The activity of the extracted complex was measured by liquid scintillation counting and the counting efficiency was found to be 40%. The calibration graph was linear in the range 0-10 pg of selenium in a final volume of 10 ml. As little as 0.01 pg of selenium can be determined in a total volume of 10 ml. The interferences due to several ions were overcome by using an aluminium hydroxide collection procedure.
A catalytic method based o n the abstraction of CN-from hexacyanoferrate(1i) b y mercury(ii) in the presence of 4-(2'-th iazolylazo)resacetop henone oxi m e was studied spectrop hotometrical I y. The met hod allows the determination of mercury(ii) in the range 0.014.9 ppm at a wavelength of 420 nm. The method was applied t o the determination of methyl-and ethylmercury chloride and the analysis of environmental water samples.
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