Automated preconcentration of Fe, Zn, Cu, Ni, Cd, Pb, Co, and Mn in seawater with analysis using high-resolution sector field inductively-coupled plasma mass spectrometry

Abstract

A rapid, automated, high-throughput analytical method capable of simultaneous analysis of multiple elements at trace and ultratrace levels is required to investigate the biogeochemical cycle of trace metals in the ocean. Here we present an analytical approach which uses a commercially available automated preconcentration device (SeaFAST) with accurate volume loading and in-line pH buffering of the sample prior to loading onto a chelating resin (WAKO) and subsequent simultaneous analysis of iron (Fe), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), lead (Pb), cobalt (Co) and manganese (Mn) by high-resolution inductively-coupled plasma mass spectrometry (HR-ICP-MS). Quantification of sample concentration was undertaken using isotope dilution for Fe, Zn, Cu, Ni, Cd and Pb, and standard addition for Co and Mn. The chelating resin is shown to have a high affinity for all analyzed elements, with recoveries between 83 and 100% for all elements, except Mn (60%) and Ni (48%), and showed higher recoveries for Ni, Cd, Pb, Co and Mn in direct comparison to an alternative resin (NOBIAS Chelate-PA1). The reduced recoveries for Ni and Mn using the WAKO resin did not affect the quantification accuracy. A relatively constant retention efficiency on the resin over a broad pH range (pH 5-8) was observed for the trace metals, except for Mn. Mn quantification using standard addition required accurate sample pH adjustment with optimal recoveries at pH 7.5 ± 0.3. UV digestion was necessary to increase recovery of Co and Cu in seawater by 15.6% and 11.4%, respectively, and achieved full break-down of spiked Co-containing vitamin B complexes. Low blank levels and detection limits could be achieved (e.g., 0.029 nmol L for Fe and 0.028 nmol L for Zn) with the use of high purity reagents. Precision and accuracy were assessed using SAFe S, D1, and D2 reference seawaters, and results were in good agreement with available consensus values. The presented method is ideal for high throughput simultaneous analysis of trace elements in coastal and oceanic seawaters. We present a successful application of the analytical method to samples collected in June 2014 in the Northeast Atlantic Ocean.

Influence of Iron, Cobalt, and Vitamin B12 Supply on Phytoplankton Growth in the Tropical East Pacific During the 2015 El Niño

“…Seawater samples for dissolved trace element analysis were collected in acid‐washed 125‐mL low‐density polyethylene sample bottles (Nalgene), filtered inline using a 0.8/0.2‐μm AcroPak1000 ™ (Pall) filter capsule. Samples were acidified with ultrapure hydrochloric acid (UpA grade, Romil) to pH 1.9 for >6 months, subject to 4‐hr UV irradiation in 30‐mL fluorinated ethylene propylene bottles, preconcentrated on a modified Sea FAST system (Elemental Scientific Inc), and then analyzed using an Element XR inductively coupled plasma‐mass spectrometer (Thermo Finnigan; Rapp et al, ). Isotope dilution and standard additions were used to quantify Fe and Co, respectively.…”

Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean

“…Concentrations of dissolved and total dissolvable Fe, Mn, and Al in seawater were determined by offline pre-concentration and isotope dilution/standard addition ICP-MS (Thermo Fisher Scientific Element2 XR) according to Rapp et al (2017). For a more detailed description of the method and measured reference materials see Sect.…”

Data trend shifts induced by method of concentration for trace metals in seawater: Automated online preconcentration vs. borohydride reductive coprecipitation of nearshore seawater samples for analysis of Ni, Cu, Zn, Cd, and Pb via ICP‐MS

“…One line of reasoning is that the Borohydride method produces lower recoveries due to trace metal analytes coprecipitation sensitivities to pH, while Online preconcentration allows for a much wider range (Biller and Bruland 2012). Another factor to consider for Online accuracy is loading rate and volume of the preconcentration column; Rapp et al (2017), for example, obtained significantly low recoveries for Ni using a resin volume of 15 μL in contrast to the 200 μL column in the current study. Sample replicates for each study recovered all analytes within 9% as relative percent difference (RPD).…”