Determination of trace amounts of uranium in aluminium nitride by fluorometric method after extraction with tributylphosphine oxide

Uranium was extracted with tributylphosphine oxide (TBPO) into toluene from 4 M hydrochloric acid solution, and determined by fluorometry following carbonate fluoride fusion. The extractability was 96 % by the second extraction from the aqueous phase after the first extraction. 1 % TBPO/toluene and 30 min shaking time was used for each extraction. The presence of 7.5 μg Fe(III) interfered with the determination, while other coexisting elements did not. Interference by Fe(III) was suppressed by adding hydroxylamine in aqueous phase. Aluminium nitride was dissolved by heating in a sealed Teflon vessel with 8 M hydrochloric acid. Trace uranium as low as 1.9 ng per sample was determined. (author)