Automated Determination of Gallium In Seawater Using seaFAST Pre-Concentration and High-Resolution Inductively-Coupled Plasma Mass Spectrometry

Authors

Melissa Gilbert, University of Southern MississippiFollow
Peng Ho, University of Southern MississippiFollow
Laura Whitmore, University of Southern MississippiFollow
Alan Shiller, University of Southern MississippiFollow

Document Type

Article

Publication Date

2-8-2023

Department

Marine Science

School

Ocean Science and Engineering

Abstract

There has been increased interest in dissolved gallium (Ga) in natural waters due to its long residence time and its usefulness in tracking water masses; however, current analytical approaches are time consuming and labor intensive (e.g., magnesium hydroxide co-precipitation method, (Mg(OH)₂)) or have concerns such as carryover and sample recovery (automated resin column extraction). Ocean observing programs, such as GEOTRACES, recover hundreds of samples per expedition. There are both logistical (sample volume) and analytical (person-hour) demands to economically collect and analyze Ga. We present an automated isotope dilution method (using 99.8% enriched ⁷¹Ga) to determine Ga in seawater utilizing commercially available equipment while addressing the challenges of a) sample volume and sample pre-concentration factor, b) instrumental interferences, c) sample-sample carryover, d) sample recovery variability, and e) improving sample detection limits, accuracy and precision. A seaFAST SC-4DXS pico (Elemental Scientific, Inc.; ESI) was used to pre-concentrate 20 mL of sample on a Nobias PA1 resin column 67-fold before analysis in medium resolution on a ThermoFisher high-resolution inductively-coupled plasma mass spectrometer (HR-ICP-MS) equipped with an APEX Q FAST enabled spray chamber (ESI) to increase signal intensity and decrease instrument interferences. The new automated seaFAST method reproduced Ga concentrations determined by the Mg(OH)₂ method, but with greater precision (RSD <4%) and a lower detection limit (0.10 pmol L⁻¹). This method is ideal for high throughput applications and can be easily implemented using commercially available equipment.

Publication Title

Analytica Chimica Acta

Volume

1241

Recommended Citation

Gilbert, M., Ho, P., Whitmore, L., Shiller, A. (2023). Automated Determination of Gallium In Seawater Using seaFAST Pre-Concentration and High-Resolution Inductively-Coupled Plasma Mass Spectrometry. Analytica Chimica Acta, 1241.
Available at: https://aquila.usm.edu/fac_pubs/20544