T. V. Shishkina

Determination of gold in geological samples by x-ray fluorescence spectrometry after extraction with tributyl phosphate

Abstract The behaviour of gold and elements impeding its x-ray fluorescence spectrometric (XRF) determination, namely zinc, lead and arsenic, was studied during their extraction from hydrochloric acid, nitric acid, and aqua regia solutions using tributyl phosphate as a solid extractant [SE(TBP)]. Extraction of gold from pulps after aqua regia leaching was found to be the most favourable approach for the quantitative and selective recovery of gold. The gold distribution ratio, DAu, is ca. 104 ml g−1. For extraction from hydrochloric acid solutions the DAu value also exceeds 104 in the whole range of gold concentrations studied (10−8−10−4 M), but it decreases substantially with increasing extraction temperature, from 5 × 105 ml g−1 at 20°C to 9 × 103 ml g−1 at 70°C. An anomalously high distribution ratio of lead, DPb ≈ 103 ml g−1, was observed during extraction from hydrochloric solutions in the presence of chlorine. This could be explained by the formation of the chloro complexes of lead(IV). An XRF method for the determination of gold in natural samples was developed, which includes back-extraction of gold from SE(TBP) using a hot 0.025 M thiourea solution, providing a thin sample layer for secondary XRF. For 25 g of sample material the limit of determination is 10 ng g−1 (10−6%). The accuracy of the technique was checked using different reference materials. The results agreed within 10%.

Determination of gold in natural waters by neutron activation and γ-spectrometry after preconcentration with tributyl phosphate as solid extractant

Abstract A method for the preconcentration of gold in natural waters at the sampling site using tributyl phosphate as a solid extractant [Se(TBP)] was developed as a preliminary step prior to the determination of gold by neutron activation and γ-spectrometry. The SE(TBP) was saturated with gaseous chlorine for extracting all gold species. In batch experiments gold was quantitatively retained on the SE(TBP) in 10 min. After extraction and washing, the SE(TBP) was ashed or back-extracted. Gold was quantitatively eluted with hot, neutral 0.025 M thiourea. The gold content of residues of ashing or eluents after evaporation was determined by neutron activation and γ-spectrometry. The detection limit for the overall procedure was 0.2 ng 1 −1 . The efficiency was tested on ‘equilibrated’ solutions prepared from river water and tracer solutions of gold. For comparison, the gold content of natural water samples was determined using preconcentration on activated charcoal.

Production of high-purity26Al

Abstract26Al is a positron emitting radioisotope of aluminium and has a half-life of 7.16×105y. In addition to annihilation γ-rays of 511 keV, there are three high energy γ-rays 1129 (2.4%), 1809 (99.73%) and 2938 (0.27%) keV.26Al is the only radioisotope of aluminium available for radiochemical applications, the half-lives of the other aluminium isotopes are seconds and minutes. The usage of26Al is very important in the investigations of the metabolism of Al in human body (for example in Alzheimer disease studies) or as a tracer in radiochemical studies. But26Al is such a long-lived isotope that the task of producing it in tangible amounts is a very difficult one.

Radioisotopes in Life Sciences. The Production of High-Pure Radionuclide Sources at FLNR, JINR

A short review of the current data concerning nuclear reactions, target chemistry and following applications of some radioisotopes as tracers is given in this report.