A new technique for quantification and speciation of 99Tc in environmental samples
Congress ttile :10th International Symposium on Environmental Radiochemical Analysis
Congress town :Oxford
Congress date :13/09/2006
Technetium is an important long half-lived multivalent radioelement to be considered in environmental monitoring. The knowledge of the redox and chemical properties of this element is required in order to predict Tc behaviour and transfer in the environment.
Given the extremely low concentration of 99Tc in the environment (10-10 M to 10-12 M) and the presence of interfering radionuclides, its determination needs a radiochemical purification of the sample matrix prior to measurement with sensitive techniques.
We have developed a new measurement technique applied to the quantification and the speciation of 99Tc in environmental samples. Indeed, we have combined a powerful separation technique, Capillary Electrophoresis (CE) with an atomic specificity, multi-elemental and extremely high sensitivity technique, Inductively Coupled Plasma Mass Spectrometry (ICPMS).
We have finalized an interface which itself may be considered as the “key to success” to allow a high separative resolution, a high analyte transport efficiency and a sensitive detection.
In the present study, we compare and discuss the separation results, without radiochemical treatment, of a mixture containing ReO4- (rhenium: technetium chemical analogue)/TcO4- /MoO4 2- obtained by both techniques, CE equipped with a UV detector and our coupling system CE-ICP-MS. We have succeeded in reaching a detection limit value equal to 10-10 M of 99Tc in using CE-ICP-MS system instead of 10-5 M in using CE.
Then, the analysis of 99Tc has been realized with our CE-ICP-MS technique and an usual technique, the extraction of Tc(VII) by a chromatographic TEVA resin prior to liquid scintillation counting. The comparison was studied firstly in waters mimicking environmental waters, secondly in a mix of pure b- emitters 99Tc / 99Mo. Instead of a time consuming separation of 99Tc from the sample matrix before measurement, we can separate online 99Tc, from the others radionuclides overlaps, by CE-ICP-MS. The CE-ICP-MS system arises as being a sensitive and fast technique for quantification and speciation of 99Tc in samples at environmental concentrations.
For migration studies, we have quantified 99Tc in Chernobyl waters by ICP-MS. Actually, there are few values of 99Tc in the environment due to nuclear counting techniques detection limits. Speciation of 99Tc in Chernobyl samples could be studied in the future by CE-ICP-MS which appears as a good environmental measurement method.
Otherwise, within the framework of environmental monitoring and storage of spent fuel, we have worked on the speciation of Tc in iron-sulphide soils, at the concentration of 10-4M and 10-7M, and compared two analytical methods, a batch-sorption and a column methods.