Determination of 226Ra in biological samples by adsorption on specific adsorbers

Abstract

The determination of 226Ra in biological samples, such as milk and grass, was studied. 226Ra analysis of cow's milk was studied starting from de-fatted milk. The proteins were eliminated by coagulation of the colloidal phase with trichloroacetic acid. Phosphorus was then removed by precipitating it as molybdophosphate and finally adsorption was carried out by using two different adsorbers in order to concentrate and purify radium. Lead rhodizonate (LEHRO) adsorbed on charcoal and partially reduced tin dioxide (PRTD) were utilised. A method for the determination of 226Ra in grass ashes was also investigated. The main interference, due to magnesium, hinders the use of LERHO, so the proposed procedure is based on adsorption of radium on PRTD at pH 9.5. The magnesium concentration was depleted by precipitating barium (carrier) and radium with calcium carbonate at pH 8 before the adsorption step. The high phosphorus concentration in grass also interferes in the determination of 226Ra; phosphorus was eliminated as above via molybdophosphate precipitation. The radium was carried by barium and spiked with 133Ba. The yield of the chemical procedure was evaluated on the basis of 133Ba activity. Radium samples were alpha-counted and the activity was evaluated with a suitable calibration curve. Both exchangers in the milk analysis and PRTD in grass analysis were shown to be helpful in order to set up an easily performed procedure, which allows many samples to be processed simultaneously. All the methods adopted were shown to be very sensitive. Under the experimental conditions used, with 1 L of milk or 5 g of grass ashes, the limit was about 3 mBq 226Ra L-1 milk and < 1 mBq 226Ra g-1 grass ashes.

Determination of 226Ra at ultratrace level in mineral water samples by sector field inductively coupled plasma mass spectrometry

“…Furthermore, because of its similarity to the alkaline earth metals, radium follows the calcium pathway in biological organisms, so it is strongly adsorbed into bones, cell and tissues where its counting activity may cause serious damage. 7,8 Recently, in the Safe Drinking Water Act, 9 the United States Environmental Protection Agency (EPA) developed regulation standards that limited the concentrations of selected contaminants in consumed drinking water. In accordance with this act, the maximum concentration level of 226 Ra in drinking water should not exceed 5 fg ml À1 .…”

“…For instance, Epov et al 3 used collision cell ICP-MS (ICP-CC-MS) to reduce the isobaric interferences which disturb the 226 Ra measurements. Limits of detection of 20 fg ml À1 were obtained for 226 Ra determination when helium and hydrogen were used as collision gases in ICP-CC-MS. Chemical separation on the cation-exchange column, 5,21 adsorption on lead rhodizonate (LEHRO) and partially reduced tin dioxide (PRTD) absorbers, 7 sequential selective extraction, 18 separation using commercially available MnO 2 resin 14 and Ra-specific solid phase extraction disks 5 have also been successfully established for radium separation in different labs. However, in all these techniques either the separation factor is not sufficient or they are relatively expensive and time consuming.…”

Hyphenation of flow injection on-line preconcentration and ICP-MS for the rapid determination of 226Ra in natural waters

“…Occurring as a relatively long-lived (t 1/2 ¼ 1622 years) intermediate isotope of the radioactive decay series of 238 U, 226 Ra is present at varying concentrations in natural samples such as soils, rocks, and waters. Owing to its high specific activity (1 pCi pg À1 ), 1 its rapid incorporation into human and animal food chains through various pathways such as food crops and drinking water, 2 and its long biological half-life in bones and tissues, which can cause radiological damage, 3 the monitoring of 226 Ra in environmental waters is crucial.…”