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

[Image: see text] Quantification of pg/L levels (i.e., 0.6 mBq/L) of radioactive technetium-99 ((99)Tc) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 ((99)Ru) and molybdenum hydride ((98)Mo(1)H) 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 × 10(–13) and 1.1 × 10(–5) for (99)Tc/Mo and (99)Tc/Ru, respectively. A classical mathematical correction using the natural isotope ratio of (99)Ru/(102)Ru was used to calculate the residues of (99)Ru. Using this optimized system, a detection limit (DL; 3σ) of (99)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 (99)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(–18) and 3.5 × 10(–9) for (99)Tc/Mo and (99)Tc/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied.