Separation of strontium-89 and -90 from calcium in milk with a macrocyclic ether

Abstract

A small amount of strontium ion (20 mg) was simply separated from a large amount of calcium ion (0.5-13.6 g) by liquid-liquid extraction using dicyclohexyl 18-crown-6 chloroform solution. The extraction was applied to a part of the procedure for determining radiostrontium in ash of milk. The overall recovery of strontium was 75% on the average for 5-10 g of milk ash. Decontamination factors for Mg, Ca, Ru, I, Cs, Ba, and La in the final fraction were 1 X 10s, 1 X 104, >1 X 10®, >1 X 10®, >2 X 10®, 2 X 10®, and 3 X 104, respectively. The chemical procedure for three samples took about 2 days.

Methodology for determination of radiostrontium in milk: a review

“…The classical procedure of milk sample pretreatment is carried out in three steps [5,18,19,21,24,26,38]; the sample is dried at about 105-110°C to a constant weight and incinerated in a muffle furnace between 400 and 600°C; then the ashes are most often dissolved in concentrated nitric acid (between 5 and 14 mol·L -1 ) except by Bouquiaux and Gillard-Baruh, who dissolved the ashes in concentrated hydrochloric acid [6,7]. Actually, this pretreatment is different for each method with respect to, the temperature chosen and sometimes the temperature gradient used, and the nitric acid concentration and temperature used for dissolution.…”

“…Although calcination pretreatment is efficient and commonly used, there is no doubt that it is time-consuming (>1 d) [4,16,25,26,31].…”

“…The chromate precipitation is also well suited to the selective extraction of 210 Pb. The strontium/yttrium separation is carried out by coprecipitation with iron hydroxide [4,24,26,49], or selective precipitation of yttrium hydroxide [25,33,39].…”

“…Kimura et al [26], among others [49], have proposed the extraction of strontium from a large amount of calcium by liquidliquid extraction with a macrocyclic ether (dicyclohexyl-18-crown-6, DC18C6) into chloroform. These methods give a sufficient decontamination factor, except for 140 Ba which follows strontium in the chemical operation.…”

“…Largely used [3,20,21,26,31,33,39,40,49] for its convenience, low background (0.5 dpm), significant efficiency (about 50%) and relative immunity from a interferences, the proportional counter is the oldest technique. Nevertheless, this counting system is unable to discriminate the b particles of each of the elements 90 Sr, 89 Sr and 90 Y. Consequently, in the case of 90 Y elimination prior to radiostrontium counting, the content of 90 Sr and 89 Sr must be evaluated by the degree of 90 Y ingrowth at some interval of time after the Sr/Y separation.…”