linear over the range 40 to 400 µg Ce-i.e., 1.6 to 16 µg ml'1 of cerium in the initial aqueous solution. The absorbance values which correspond to these concentrations in the aqueous solution are 0.07 and 0.73. A sensitivity for cerium by this indirect method of 0.093 µg ml'1 (for 1% absorption) was obtained. The procedure blank was reproducible and gave rise to an absorbance of 0.04 at 313.2 nm vs. an isobutyl acetate solvent blank.The virtually quantitative extraction of phosphate into the isobutyl acetate medium was demonstrated by taking several different known weights of cerium through the procedure. The MPA in the final isobutyl acetate phases was decomposed and back-extracted by shaking with 10 ml of 4M ammonia solution. The solutions were then diluted to 25 ml with distilled water. The concentration of
A method for the determination of selenium in whole blood using a new Zeeman graphite furnace system is presented. A two-part chemical modifier was used in which palladium is reduced to the metallic state in the graphite tube. This reduced palladium modifier gave enhanced thermal stability and sensitivity for selenium compared with the often used nickel modifier. The palladium modifier is injected into the graphite tube prior to adding the blood which has been previously diluted (1 + 4) with a mixture of 0.5% M'VTriton X-100,0.125% WVantifoam B and 0.25% m/VL-ascorbic acid, the reducing agent. Optimisation of the analytical parameters is described. Calibration was established using the standard additions method, with additions being made automatically by an autosampler. Precisions were in the range 2.5-8.7% relative standard deviation for levels of selenium in whole blood of 80.5-159 ng ml-1.
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