Determination of picomolar to sub-nanomolar trace metals in seawater using an alternative chelating resin

In this study, we investigated the potential use of a chelating resin that immobilizes an amine with an iminodiacetic acid group (InertSep ME-2) for trace-metal analysis in natural seawater. Seven trace metals (Mn, Fe, Co, Ni, Cu, Zn, and Pb) were quantitatively preconcentrated onto the InertSep ME-2 chelating resin, eluted with nitric acid, and analyzed using high-resolution inductively coupled plasma mass spectrometry. The blank values and detection limits obtained using our method were at the sub-nanomolar level for most trace metals. These blank values were generally comparable to, or lower than, those previously reported for other chelating resins, including NOBIAS Chelate PA-1 and Toyopearl AF-Chelate-650 M. The accuracy and precision of our method were confirmed by analyzing reference seawater samples, and the results for the open-water samples were consistent with those obtained in an independent laboratory. The established preconcentration procedure was successfully applied to determine trace metal concentrations in natural seawater collected from the northwestern Pacific Ocean. Our method, which employs the InertSep ME-2 chelating resin, is sufficiently accurate for studying trace metals in open-ocean water at picomolar- to sub-nanomolar-level concentrations.