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) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 (Ru) and molybdenum hydride (MoH) at 3-11 orders of magnitude higher concentrations. Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) with oxygen (O) 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 × 10 and 1.1 × 10 for Tc/Mo and Tc/Ru, respectively. A classical mathematical correction using the natural isotope ratio of Ru/Ru was used to calculate the residues of Ru. Using this optimized system, a detection limit (DL; 3σ) of Tc 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, 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 × 10 and 3.5 × 10 for Tc/Mo and Tc/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied.