Analysis of hydride-forming elements using ICP-OES

Significance of the topic

Trace analysis of hydride-forming elements is critical for environmental and public health monitoring. Regulations such as EPA limits for arsenic, mercury, antimony, selenium and bismuth in drinking water drive the need for highly sensitive analytical methods. Conventional ICP-OES introduction systems face reduced sensitivity at UV wavelengths due to absorption, making detection of these elements challenging at trace levels. Hydride generation offers a route to enhance sensitivity and meet regulatory requirements.

Goals and overview of the study

• Evaluate the performance of Thermo Scientific iCAP PRO Series ICP-OES equipped with basic and integrated hydride generation sample introduction kits.
• Compare detection limits, linearity and interference resistance for arsenic, antimony, bismuth, selenium and mercury versus a standard sample introduction system.

Methodology and experimental approach

Hydride-forming analytes in acidified solutions react with sodium borohydride to produce volatile hydrides introduced into the plasma. Two configurations were tested:

• Basic hydride generation kit delivering acidified sample and reducing agent to a T-piece upstream of the nebulizer, allowing simultaneous analysis of additional elements.
• Integrated hydride generation kit with a dedicated gas–liquid separator and direct argon carrier gas introduction for improved hydride transfer efficiency.

Pre-reduction steps for oxidation state adjustment were applied for arsenic, antimony and selenium. Calibration standards were prepared in matching acid and reagent matrices over 0.1–10 µg·L-1. Data acquisition used Qtegra ISDS Software with eUV and full range modes to select interference-free wavelengths.

Used instrumentation

• Thermo Scientific iCAP PRO, PRO XP and PRO XPS ICP-OES systems in axial viewing mode
• Basic and integrated hydride generation accessory kits
• Teledyne CETAC ASX-560 autosampler
• Qtegra ISDS Software for method development, data acquisition and processing

Main results and discussion

• Integrated kit achieved limits of detection as low as 0.015 µg·L-1 for arsenic and 0.004 µg·L-1 for mercury, with linearity coefficients above 0.999
• Basic kit improved LODs by an order of magnitude compared to standard introduction, enabling simultaneous multi-element analysis
• BEC and LOD values for hydride-forming elements were well below EPA regulations, demonstrating interference-free performance
• Performance matched or exceeded hydride generation AAS and approached ICP-MS capabilities for mercury

Benefits and practical applications

The enhanced sensitivity enables routine quality assurance and environmental monitoring laboratories to meet stringent regulatory limits. The ability to analyze hydride and non-hydride elements simultaneously streamlines workflows. The robust method supports trace level determinations in water, food and biological matrices.

Future trends and potential applications

• Integration of automated sample preparation and hydride generation for high-throughput monitoring
• Extension to speciation analysis by coupling with separation techniques
• Development of microflow hydride generation to further reduce reagent consumption and detection limits
• Application in emerging fields such as nanomaterial characterization and isotope ratio analysis

Conclusion

The study demonstrates that hydride generation accessories significantly improve the analytical performance of ICP-OES for arsenic, antimony, bismuth, selenium and mercury. The integrated kit delivers superior sensitivity and low detection limits, fulfilling regulatory requirements and expanding the capabilities of routine trace element analysis.

References

1. United States Environmental Protection Agency. National primary drinking water regulations
2. Thermo Scientific Application Note 43374. Analysis of Hydride Forming Elements with iCAP 7000 Plus ICP-OES and Basic Hydride Generator
3. Thermo Scientific Technical Note 73763. iCAP PRO Series ICP-OES Detection Limits in Axial View