X-ray fluorescence spectrometric determination of copper in pure iron after precipitation.

Abstract

Trace amount of copper (II) was quantitatively precipitated with rubeanic acid from aqueous solution of pH 6.06.4. A linear calibration curve for the X-ray fluorescence determination was obtained over the range 0.150 μg of copper. The relative standard deviation of the determination was 1.4% in five runs for 10 μg of copper, and the sensitivity was 60 cps/μg Cu. The following amounts of foreign ions were tolerated in the determination of 20μg of copper : Fe(III) 500 mg, Co(II) 5 mg and Ni(II) 1 mg. The procedure is as follows : Dissolve a sample in hydrochloric acid and hydrogen peroxide. Add 5 ml of 40% tartaric acid solution, adjust the pH to 6.06.4 with aqueous ammonia, and then add 2 ml of 0.1 % rubeanic acid solution. Collect the resulting precipitate on a membrane filter (25 mm, 0.2 μm) and wash with water. After drying the precipitate at room temperature, measure the X-ray intensity of Cu Kα line (2θ=45.05°) and that of background at an angle (2θ) 46.0°, in a vacuum for 40 s by using a molybdenumtarget tube (50 kV, 30 mA), a LiF (2 0 0) crystal and a scintillation counter.