Low-blank method for the offline batch analysis of the low concentration of dissolved lead in natural waters and its application to natural waters, including the tropical Northwest Pacific Ocean

In this study, Presep® PolyChelate resin was utilized for the offline batch extraction process and then combined with the isotope dilution method for the analysis of low concentrations of dissolved lead (Pb) in freshwater and seawater. The application of Presep® PolyChelate resin further lowered the procedural blank by reducing the amount of resin beads and buffer solution that were added with an 8-fold preconcentration. The adsorption and elution times were shortened to 2 d and 30 min, respectively, and > 85% recovery was achieved. The total procedural blank and detection limit were 0.2 ± 0.1 pmol/kg and 0.2 pmol/kg, respectively. The accuracy of this method was also verified using GEOTRACES intercalibration SAFe seawaters, with concentrations of 48.0 ± 0.5 pmol/kg (n = 3) and 27.0 ± 0.7 pmol/kg (n = 3) observed for SAFE S and D2, respectively. Full-depth profiles of dissolved Pb concentrations collected during the 2016 tropical Northwest Pacific Ocean cruise were analyzed. The dissolved Pb concentration increased from 30 pmol/kg at the surface to 50 pmol/kg at the subsurface and it then decreased to 8–9 pmol/kg in the bottom waters.