Agilent ICP-MS Journal (February 2007 – Issue 30)

Significance of the Topic

The precise quantification of trace elements in complex matrices underpins regulatory decisions, environmental monitoring and metallomic research. In hypersaline environments such as the Great Salt Lake, accurate selenium determination at sub-ppb levels is critical to protect wildlife. Upgrading existing ICP-MS instruments with collision and reaction cell technology expands analytical scope, while data processing innovations and collaborative networks enhance laboratory performance.

Objectives and Study Overview

This summary integrates key developments presented in Agilent ICP-MS Journal Issue 30, February 2007, including:

• Comparison of analytical techniques for trace selenium in the Great Salt Lake
• Upgrade of an Agilent 7500i to ORS-equipped 7500ce and its operational impact
• Isotope dilution applications on 7500ce employing custom ChemStation databases
• Features of the new Fileview Plus data extraction software
• Establishment of the Metallomics Center of the Americas and service updates

Methodology and Instrumentation

• Hydride generation atomic absorption (HGAA), graphite furnace AAS (GFAA), conventional ICP-MS (Agilent 7500a), DRC ICP-MS and octopole reaction cell ICP-MS (Agilent 7500ce) for selenium analysis
• Round-robin testing with blind spiked and native lake water samples to assess accuracy, precision and bias
• Operational modes on the 7500ce: hydrogen reaction cell for selenium (m/z 78, 94, 96) and helium collision cell for polyatomic interference removal
• Laboratory upgrade of a 7500i to ORS-ICP-MS: hardware/software enhancements, retention of ISIS auto-dilution, later removal of ISIS to reduce sample and waste volumes
• Exact matching double isotope dilution calculations using custom ChemStation databases with built-in replicate ratio, SD and uncertainty computations
• Fileview Plus software for real-time sequence data import, customizable grid views, MDL/IDL/BEC calculations, CCV/CCB tracking and internal standard plotting

Main Results and Discussion

• In high salt lake waters, only hydride AA and ORS-ICP-MS yielded accurate Se results; conventional ICP-MS, GFAA and DRC produced significant positive bias
• Octopole reaction cell ICP-MS offered low detection limits (<10 ppt), multielement analysis, minimal spectral interferences and simplified sample preparation
• Removal of the ISIS system reduced sample consumption from ~7 mL to <1 mL and decreased waste disposal costs; analysis time per sample was shortened
• Helium collision mode effectively eliminated chloride-based polyatomic interferences, while hydrogen mode removed oxygen-based overlaps for selenium
• Custom databases streamlined isotope dilution workflows, consolidating raw counts, replicate data and uncertainty components into a single interface
• Fileview Plus automated data extraction, enhancing productivity and facilitating instrument performance monitoring

Benefits and Practical Applications

The adoption of ORS-ICP-MS and advanced software tools delivered:

• High sensitivity and low detection limits for trace elements in challenging matrices
• Improved accuracy, precision and reduced interference bias
• Simultaneous multielement capability supporting environmental, industrial and biochemical analyses
• Reduced sample volume requirements and streamlined waste handling
• Faster throughput and simplified daily operation with rapid tuning in multiple modes
• Integrated data processing workflows for isotope dilution and routine QC calculations

Future Trends and Potential Applications

Anticipated developments include:

• Expanded metallomics research via specialized centers and international collaborations
• Further enhancements in collision/reaction cell chemistries to tackle emerging interferences
• Integration of real-time data analytics and machine learning for method optimization
• Broader certification of ORS-ICP-MS methods by regulatory agencies for saline and biological matrices
• Advances in software customization to support complex isotopic and speciation studies

Conclusion

Evaluation of multiple techniques confirmed ORS-ICP-MS as the method of choice for trace selenium in hypersaline water due to its sensitivity, multielement capacity and minimal bias. Laboratory upgrades to ORS technology, combined with custom data solutions such as isotope dilution databases and Fileview Plus, significantly enhance analytical efficiency and data integrity. Collaborative initiatives like the Metallomics Center of the Americas foster cutting-edge research and method development across disciplines.

References

• Utah Department of Environmental Quality, Great Salt Lake Water Quality Steering Committee web page
• The Nature Conservancy, Great Salt Lake Science information
• Santamaria-Fernandez R., Evans P., Wolff-Briche C.S.J. & Hearn R. J. Anal. At. Spectrom., 2006, 21, 413
• Wolff-Briche C.S.J. Metrologia, 2003, 40, 08010
• Catterick T., Fairman B., Harrington C.F. J. Anal. At. Spectrom., 1998, 13, 1009
• ISO Guide to the Expression of Uncertainty in Measurement, 1993