Spectrophotometric method is a simple and effective in situ analytical method for contaminants monitoring, but further improvement of its sensitivity and detection limit for radionuclides determination remains highly desirable. Herein, we report a simple and highly sensitive thiocyanate spectrophotometric method for the determination of radioactive Tc(VII) by studying its chemical analogue Re(VII) in different aqueous media. The colorless thiocyanate reacted with Re(VII) in hydrochloric acid solution in the presence of SnCl2 producing a stable colored Re(IV)-SCN complex, which was extracted into ethyl acetate and then measured at 427 nm. Under optimized conditions, a strong linear relationship can be obtained in the range of 0.25–10 mg L−1 for Re(VII) with R2 value > 0.9942, and the sensitivity of the method was found to be 0.004 μg cm−2 with detection limit of 0.027 mg L−1. This assay provides highly sensitive detection of Re(VII) in environmental media that is high in NO3−, Cu2+, and Fe3+. We applied it to the determination of Re(VII) in the wide range of background solutions, including deionized water, groundwater, and seawater, and analysis results showed that none of the molar absorptivities for both groundwater and seawater backgrounds was statistically different from the deionized water background when the paired Student’s t test, at 95% confidence level, was applied. The operational simplicity, accuracy, and precision of the proposed method suggest that it can be a good alternative for the in situ analysis of pertechnetate in environmental media.
Pertechnetate Spectrophotometry Thiocyanate High sensitivity In situ analysis
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