Lanthanoid analysis in seawater by seaFAST-SP3™ system in off-line mode and magnetic sector high-resolution inductively coupled plasma source mass spectrometer

Analysis of lanthanoids in seawater is challenging due to the complex matrix (∼35 g L(−1) TDS) and low dissolved concentrations (in ng L(−1)). A 4-step strict analytical protocol and state-of-the-art technology were implemented and validated in this study. The 4-steps method involves the 1) sample filtration and acidification (pH<2); 2) pre-concentration by the matrix separation system, 3) off-line injection of the eluted sample; and 4) determination of lanthanoids by high-resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). Since there are no certified values for lanthanoids in seawater are available, the method validation was done by analyzing SLEW-3 (estuarine water reference samples) and comparing with other reports and artificial seawater (100 ng L(−1) lanthanoid multi-element standard solutions). SLEW-3 recovery varied from 78.6% to 106% and in artificial samples it ranged from 87 to 110%. Low recovery can be explained by complex organic in seawater, because the UV oxidation was not performed in the acidified samples. The variation was ≤10%, except for Gd, Tb, and Yb (11–13.75%). Blanks varied between 0.01 and 0.07 ng L(−1), except for La and Ce (0.13–0.21 ng L(−1)). Blanks represent <5% SLEW-3 values and <1% synthetic seawater. The procedural detection limit varied from 0.01 to 0.03 ng L(−1). • Lanthanoids as geochemical tracers in seawaters; • A 4-step strict analytical protocol and state-of-the-art technology for lanthanoids analyses in seawaters; • Sample pre-concentration system for matrix separation for the detection of ultra-low lanthanoids levels.