Evaluation of procedures for determination of Ra-226 in water by α-particle spectrometry with emphasis on the recovery

Optimal methods for preparation, separation, and determination of radium isotopes in environmental and biological samples

In recent years, radium has attracted considerable attention primarily because of the rapid increase in unconventional (fracking) drilling technology in the United States and around the world. One of the major radionuclides of interest in unconventional drilling wastes is radium isotopes (²²⁴Ra, ²²⁶Ra, ²²⁸Ra). To access long-term risks associated with radium isotopes entering into the environment, accurate measurements of radium isotopes in environmental and biological samples are crucial. This article reviews many aspects of radium chemistry, which includes recent developments in radiochemical separations methods, advancements in analytical techniques followed by a more detailed discussion on the recent trends in radium determination.

Determination of 226Ra in Urine Using Triple Quadrupole Inductively Coupled Plasma Mass Spectrometry

Measuring 226Ra in urine at low levels is critical for both biomonitoring and radiological emergency response. Here we report a new analytical method to quantify 226Ra, as developed and validated by a simple dilute-and-shoot procedure, followed by Inductively Coupled Plasma-triple quadrupole-mass spectrometry detection using 'No Gas MS-MS' mode. The method provides rapid and accurate results for 226Ra with a limit of detection (LOD) down to 0.007 ng/l (0.26 Bq/l). This LOD is well below the recommended action levels for 226Ra detection in children and pregnant women (C/P) set by the Clinical Decision Guide (NCRP Report #161). Results for 226Ra obtained by this method are within ±7.0% of the target values of standard reference materials spiked in the urine.

Determination of 226Ra at low levels in environmental, urine, and human bone samples and 223Ra in bone biopsy using alpha-spectrometry and metrological traceability to 229Th/225Ra or 226Ra

²²⁶Ra is a natural radioelement emitting α and γ radiations. It can be highly concentrated in TENORM materials from the petroleum or fertilizer industries. In Switzerland, ²²⁶Ra is currently a radioactive inheritance problem from the watch industry. Furthermore, ²²³Ra is a radium isotope used in nuclear medicine to treat bone metastasis. There exist several methods to measure radium using alpha or gamma spectrometry or using ²²²Rn emanation technique. The limitations of these methods are due to the required detection limits and the nature of the samples. When using alpha spectrometry to reach very low detection limits, critical technical hitches often arise because of the difficulties in separating radium from barium, in removing organics eluted from the separating chromatography column, and in plating radium. Moreover, overall chemical recovery of radium is often not reproducible, depending on the studies. Here we propose a method that separates radium from other alkaline-earth cations using cation exchange chromatography and selective complex formation by EDTA and DCTA. Radium is completely free of the ²²⁹Th tracer and its daughter products, particularly ²²⁵Ac. Organics from the column are removed in a further purification step so that radium can be plated with acceptable yields in a HCl/HNO₃/ethanol solution. We successfully applied the method to soil, water, urine and human bone samples and further extended it to the determination of ²²³Ra in a bone biopsy, using ²²⁶Ra as an internal tracer.

Evaluation of procedures for (226)Ra determination in samples with high barium concentration by α-particle spectrometry

The γ emitter (133)Ba is the most often used tracer in determination of (226)Ra by α-particle spectrometry. If the source for α-particle spectrometry is prepared by microcoprecipitation, a high Ba concentration causes a thicker source layer which results in reduced counting efficiency due to self-absorption on the α spectrometer and consequently lower result for (226)Ra, while not effecting the measurement of (133)Ba in γ-ray spectrometry. If the electrodeposition is used, recoveries of deposited Ra and Ba are not necessarily the same and impurities of other α emitters may interfere with the α spectrum.

Rapid determination of 226Ra in urine samples

A new radiochemical separation method has been developed for rapid analysis of (226)Ra in urine samples. In this method, radium is separated from urine matrix using cation and anion exchange column chromatography. A (224)Ra tracer is added, together with its parent in the (228)Th standard, for chemical recovery correction. After separation, the sample is precipitated with hydrous titanium oxide and then prepared for counting by creating a thin-layer counting source using BaSO(4) micro-precipitation. The radium isotopes are then counted by alpha spectrometry. Replicate spike and blank samples were analysed for validation of the procedure. The detection limit was determined to be 0.22 Bq l(-1) with 4 h of counting for 20 ml of urine sample. Using this method, the results can be reported within an 8 h turn-around time. This method is suitable for quick dose assessment of (226)Ra exposure following a radiation emergency.