Determination of Technetium and Its Speciation by Surface-Enhanced Raman Spectroscopy

Abstract

Technetium-99 (Tc) is an important radionuclide of concern, and there is a great need for its detection and speciation analysis in the environment. For the first time, we report that surface-enhanced Raman spectroscopy (SERS) is capable of detecting an inorganic radioactive anion, pertechnetate (TcO4-), at approximately 10(-7) M concentration levels. The technique also allows the detection of various species of Tc such as oxidized Tc(VII) and reduced and possibly complexed Tc(IV) species by use of gold nanoparticles as a SERS substrate. The primary Raman scattering band of Tc(VII) occurs at about 904 cm-1, whereas reduced Tc(IV) and its humic and ethylenediaminetetraacetic acid (EDTA) complexes show scattering bands at about 866 and 870 cm-1, respectively. Results also indicate that Tc(IV)-humic complexes are unstable and reoxidize to TcO4- upon exposure to oxygen. This study demonstrates that SERS could potentially offer a new tool and opportunity in studying Tc and its speciation and interactions in the environment at low concentrations.

Determination of Band Structure Parameters and the Quasi‐Particle Gap of CdSe Quantum Dots by Cyclic Voltammetry

“…Our results represent the first use of SERS to detect RDX in a contaminated groundwater at an environmentally relevant concentration, although the SERS technique has been previously demonstrated to detect a range of pollutants such as TNT, perchlorate, pertechnetate, and uranium in groundwater at low concentrations 48–50. Our work further demonstrates the potential for developing a field SERS detector coupled with a portable Raman spectrometer.…”

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

“…The lack of any observed effect by EDTA on solubility weakens the argument presented by Stalmans et al (1986), in which a lack of interaction between technetium and EDTA was cited as evidence for strong Tc-OM interactions (see above). Gu and Ruan (2007), on the other hand, reported limited complexation between Tc(IV) and EDTA or humic acids using a Surface-Enhanced Raman Spectroscopy (SERS) technique. Low concentrations of Tc(IV)(aq) can be detected by Raman spectroscopy when technetium sorbs onto nanoparticles of gold that have surfaces modified with positively charged dimethylamine functional groups.…”

Determination of technetium-99 in environmental samples: A review

“…Compared with the continuous flow injection with peristaltic pump, the sequential injection system is more flexible and attractive. For example, the syringe pump can eliminate the frequent pump tubing replacement and tedious flow rate 58 calibrations. However, as mentioned above, the method can only be applied for analysis of small samples, and is not suitable for analysis of environmental samples with low level of 99 Tc.…”

“…In reductive conditions, Tc(IV) is the most stable oxidation state and strongly hydrolyzes in aqueous solutions and is very stable as TcO 2 in the absence of water [54]. In addition, various complexes of Tc(IV) can be formed in the presence of organic or inorganic ligands such as carbonate, EDTA, citrate and natural humic substances [55][56][57][58].…”