An ICP-MS procedure to determine Cd, Co, Cu, Ni, Pb and Zn in oceanic waters using in-line flow-injection with solid-phase extraction for preconcentration.
An automated procedure including both in-line preconcentration and multi-element determination by an inductively coupled plasma mass spectrometer (ICP-MS) has been developed for the determination of Cd, Co, Cu, Ni, Pb and Zn in open-ocean samples. The method relies on flow injection of the sample through a minicolumn of chelating (iminodiacetate) sorbent to preconcentrate the trace metals, while simultaneously eliminating the major cations and anions of seawater. The effectiveness of this step is tested and reliability in results are secured with a rigorous process of quality assurance comprising 36 calibration and reference samples in a run for analysis of 24 oceanic seawaters in a 6-h program. The in-line configuration and procedures presented minimise analyst operations and exposure to contamination. Seawater samples are used for calibration providing a true matrix match. The continuous automated pH measurement registers that chelation occurs within a selected narrow pH range and monitors the consistency of the entire analytical sequence. The eluent (0.8M HNO3) is sufficiently strong to elute the six metals in 39 s at a flow rate of 2.0 mL/min, while being compatible for prolonged use with the mass spectrometer. Throughput is one sample of 7 mL every 6 min. Detection limits were Co 3.2 pM, Ni 23 pM, Cu 46 pM, Zn 71 pM, Cd 2.7 pM and Pb 1.5 pM with coefficients of variation ranging from 3.4% to 8.6% (n=14) and linearity of calibration established beyond the observed concentration range of each trace metal in ocean waters. Recoveries were Co 96.7%, Ni 102%, Cu 102%, Zn 98.1%, Cd 92.2% and Pb 97.6%. The method has been used to analyse ~800 samples from three voyages in the Southern Ocean and Tasman Sea. It has the potential to be extended to other trace elements in ocean waters.
CSIRO Wealth from Oceans National Research Flagship and Centre for Australian Weather and Climate Research-A Partnership of CSIRO and the Bureau of Meteorology, GPO Box 1538, Hobart 7001, Tasmania, Australia; CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart 7001, Tasmania, Australia. Electronic address: Jeanette.OSullivan@csiro.au.
Jeanette E
JE
O'Sullivan
Roslyn J
RJ
Watson
Edward C V
EC
Butler
D057205:Automation, Laboratory; D002138:Calibration; D002413:Cations, Divalent; D002614:Chelating Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007098:Imino Acids / Q000737:chemistry*; D057230:Limit of Detection; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods; D019216:Metals, Heavy / Q000032:analysis*; D012015:Reference Standards; D015203:Reproducibility of Results; D012623:Seawater / Q000737:chemistry*; D052616:Solid Phase Extraction; D013054:Spectrophotometry, Atomic / Q000295:instrumentation / Q000379:methods; D014131:Trace Elements / Q000032:analysis*
D002413:Cations, Divalent; D002614:Chelating Agents; D007098:Imino Acids; D019216:Metals, Heavy; D014131:Trace Elements; C008109:iminodiacetic acid
Automated; ICP-MS; Iminodiacetate; In-line; Seawater; Trace elements