The effect of sample matrix quenching on the measurement of trace uranium concentrations in aqueous solutions using kinetic phosphorimetry

Sand samples collected on the beaches of the “radioactive” Brazilian town of Guarapari were first separated by flotation in bromoform and successively divided into various magnetic fractions with a Franz isodynamic separator. Concentrations of background radionuclides in samples of monazite, ilmenite, and zircon were determined by a γ-ray spectrometer. Chemical composition of monazite, ilmenite, and magnetite were assessed by means of an electron microprobe. Monazite resulted to be relatively rich in ThO₂ whose abundance ranged from 5.3 to 7.7 (wt%).