Online Solid-Phase Extraction-Inductively Coupled Plasma- Quadrupole Mass Spectrometry with Oxygen Dynamic Reaction for Quantification of Technetium-99

Quantification of pg/L levels (i.e., 0.6 mBq/L) of radioactive technetium-99 (Tc-99) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 (Ru-99) and molybdenum hydride ((MoH)-Mo-98-H-1) at 3-11 orders of magnitude higher concentrations. Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) with oxygen (O-2) dynamic reaction cell (online SPE-ICP-MS-DRC) was shown to be a thorough automatic analytical system, circumventing the need for human handling. At three stepwise separations (SPE-DRC-Q mass filters), we showed that interference materials allowed the coexistence of abundance ratios of 1.5 x 10(-13) and 1.1 x 10(-5) for Tc-99/Mo and Tc-99/Ru, respectively. A classical mathematical correction using the natural isotope ratio of Ru-99/Ru-102 was used to calculate the residues of Ru-99. Using this optimized system, a detection limit (DL; 3 sigma)( )of Tc-99 was 9.3 pg/L (= 5.9 mBq/L) for a 50 mL injection and sequential measurements were undertaken at a cycle of 24 min/sample. For the measurement of a lower concentration of Tc-99, an AG1-X8 anion-exchange column was used to study 20 L of seawater. Its DL was approximately 1000 times greater than that of previous methods (70.0 fg/L). Thus, this method withstands coexistences of 5.8 x 10(-18) and 3.5 X 10(-9) for Tc-99/Mo and Tc-99/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied.

Automated summary

A fully automated analytical system was demonstrated to accurately measure radioactive technetium-99 at very low concentrations, avoiding interference from isobaric and polyatomic sources.