A group of Chinese researchers developed a method for the speciation of rhenium using the hyphenated technique of capillary electrophoresis-inductively coupled plasma mass spectrometry. Since the rhenium species are known as the analogues of technetium, the proposed method retains the great potential for the speciation analysis of 99Tc in various samples.
Background:Technetium-99 (99Tc) is mainly generated by the thermal neutron fission of 235U and 239Pu and is released to the environment from spent fuel reprocessing plants and nuclear weapon tests. 99Tc is a radioactive environmental hazard with a long half-life of 2.1 x 105 years. The toxicity, bioavailability, and mobility of 99Tc is seriously dependent on its chemical forms in the environment. While the high solubility of TcO4- allows for its migration through underground water, TcO4- can be readily reduced to low-valence technetium (oxidation state < VII) under geochemically reducing conditions, mainly occurring as the particle form of TcO2 with highly reduced mobility. Therefore, for an improved understanding of its behaviour, to monitor the process of fuel reprocessing and storage conditions for waste materials, speciation analysis of Tc is mandatory. Hyphenation of a separation technique such as high performance liquid chromatography (HPLC) or capillary electrophoresis (CE) with sensitive detection by inductively coupled plasma mass spectrometry (ICP-MS) are the most frequently used approaches for such speciation analysis. For the speciation analysis of radioactive elements, CE has the big advantage over HPLC of much lower injection volumes and fast analysis, reducing the radiological exposure to operators. However, since ICP-MS is a mass-flow detector and CE does not provide a high mass-flow, CE is not the dream partner for hyphenation with ICP-MS. Anyhow, key problems that hinder the CE-ICP-MS hyphenated technique, such as flow rate matching, interface and nebulizer design have been addressed and commercially CE-ICP-MS systems are available.
The new study:In view of such CE-ICP-MS developments, a group of Chinese researchers now aimed at the use of such technique for the speciation analysis of Re(VII) and Re(IV) as a model for the determination of Tc(VII)/Tc(IV). The researchers used an electrospray ionization source sprayer as a nebulizer for sample introduction into the ICP-MS. A sheath liquid was introduced to compensate the suction effect of the pneumatic nebulizer and to close the electro-circuit of CE. A HPLC six-way valve with a 5 µL sample loop was used to directly introduce samples bypassing the CE system. This direct sample introduction path was used for the determination of the total Re concentration. Since a standard for Re(IV) was not available, the Re(IV) concentration was calculated as the difference of total Re and Re(VII). To demonstrate the feasibility of the developed system on the speciation analysis of TRe, Re(IV), and Re(VII), the speciation analysis of the products from the reduction of 600 μg/L KReO4 with 5 mg/L SnCl2 was undertaken. After optimization of the CE system, complete separation was obtained within 30 min. The detection limits under optimized conditions were 0.02 µg/L for TRe and 0.01 µg/L for Re(VII), respectively.
The authors concluded that the developed method seems to be a promising candidate for the speciation analysis of
99Tc contaminated environmental samples, for the study of
99Tc redox kinetics as well as the purity analysis of radiopharmaceuticals.
The cited study:
Dan Zhou, Yao Lin, Haoqi Long, Yuwei Xu, Bo Wang, Liang Xian, Chuanqin Xia, Xiandeng Hou, Chengbin Zheng,
Simultaneous total and speciation analysis of rhenium by capillary electrophoresis-inductively coupled plasma mass spectrometry, Spectrochim. Acta Part B, 180 (2021) 106211.
DOI: 10.1016/j.sab.2021.106211
Used Instrumentation:
Agilent Technologies - 1260 infinity HPLC Related studies (newest first): D. Kaliba, M. Sticha, I. Jelinek, J. Polakova, J. Radova,
Application of capillary electrophoresis to the separation of rhenium complex of 1,2,3-trihydroxybenzene, Monatsh. Fu. Chem., 148 (9) (2017) 1619–1624.
DOI: 10.1007/s00706-017-1982-0
K.L. Shi, X.L. Hou, J.X. Qiao, S.X. Jun, P. Roos, W.S. Wu,
Analysis of technetium species and fractions in natural seaweed using biochemical separation and ICP-MS measurement, Anal. Chem. 88 (23) (2016) 11931–11937.
DOI: 10.1021/acs.analchem.6b03837 Estela Reinoso Maset, Stephanie H. Sidhu, Andrew Fisher,
Andrew Heydon, Paul J. Worsfold, Andrew J. Cartwright, and Miranda J. Keith-Roach, Effect of organic co-contaminants on technetium and rhenium speciation and solubility under reducing conditions, Environ. Sci. Technol., 40 (2006) 5472–5477.
DOI: 10.1021/es061157f
X.L. Liu, F. Poineau, M. Fattahi, B. Grambow, L. Vichot,
Speciation of Tc(IV) in chloride solutions by capillary electrophoresis, Radiochim. Acta, 93 (2005) 305–309.
DOI: 10.1524/ract.93.5.305.64276
M. Kohlícková, V. Jedináková-Krízová,
The study of various rhenium compounds by capillary electrophoresis, J. Radioanal. Nucl. Chem. 246 (2000) 549–556.
DOI: 10.1023/A:1006736822008 R. Jankowsky, B. Noll, B. Johannsen,
Capillary electrophoresis of 99mtechnetium radiopharmaceuticals, J. Chromatogr. B 724 (1999) 365–371.
DOI: 10.1016/S0378-4347(98)00577-5
S. Uchida, K. Tagami,
Improvement of Tc separation procedure using achromatographic resin for direct measurement by ICP-MS, Anal. Chim. Acta, 357 (1997) 1–3.
DOI: 10.1016/S0003-2670(97)00562-X
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