Mic. Cantagallo et Igr. Gutz, CATALYTIC DETERMINATION OF TRACES OF URANIUM IN ROCKS BY CHRONOCOULOMETRY, Electroanalysis, 6(11-12), 1994, pp. 1115-1118
The chronocoulometric method for the determination of trace levels of
uranium based on the catalytic reduction of nitrate, described in a pr
eceding article, was applied and evaluated with real and synthetic sam
ples. Samples with complex matrixes like rocks were first solubilized
in hot acid (HF + HNO3) by digestion under pressure in a PTFE bomb. Wh
en necessary, liquid-liquid extraction with tri-n-butyl phosphate (TBP
) followed by reversion to aqueous phase was used for previous separat
ion of interferents. Results for a feldspar, a phosphorite, and three
granitic rock samples, containing uranium in the range of 2 to 100 ppm
, are in good agreement with those obtained by other techniques such a
s X-rw fluorescence, isotopic dilution-mass spectrometry (ID-MS), and
instrumental activation analysis (differences of 4 to 16% in relation
to the unweighted mean for different techniques).