M. Koide, K. Bruland
Mar 1, 1975
Citations
2
Influential Citations
85
Citations
Quality indicators
Journal
Analytica Chimica Acta
Abstract
Abstract An isotopic dilution method has been developed for the determination of 226Ra and 228Ra in sea water and sediments with 223Ra as a yield tracer. An alternative procedure which obviates the need for 223Ra is demonstrated for sediments by the assay of 224Ra and 228Th which occur naturally in sediments. In addition, a direct method for β-counting 228Ra–228Ac is proposed. Radium, polonium, thorium and uranium isotopes and 210Pb are coprecipitated from sea water with aluminum phosphate carrier. The radium and lead-210 are coprecipitated with lead nitrate in sediment leachings. All radium procedures utilize identical chemical isolation and the cathodic electrodeposition of radium. Subsequently, the α-radiation emitted by 226Ra, 223Ra and 224Ra is determined by pulse-height analysis: the 228Ra-228Ac and 210Pb-210Bi are measured by low background anticoincidence β-counting techniques. This method was used for samples containing 10-11–0.5 · 10-12 g of 226Ra and 10-13–10-15 g of 228Ra and gave a precision of 3–6% and 5–10% respectively, even though radium levels an order of magnitude less can be measured. The 226Ra method is applicable to all environmental samples, whereas 228Ra determinations are limited to applications where the 228 Ra 226 Ra activity ratio is greater than 0.1. This method is especially attractive for studies of parent-daughter disequilibria.