Measuring Arsenic in Water

Importance of Topic

Arsenic contamination in drinking water represents a significant global health hazard. The World Health Organization has established a guideline limit of 10 µg/L for arsenic, reflecting its toxicity and prevalence in water sources through natural and industrial processes. Accurate, sensitive monitoring of trace arsenic levels is essential for regulatory compliance and public safety.

Objectives and Study Overview

This application brief aims to demonstrate an automated, intelligence-driven approach to optimize graphite furnace atomic absorption spectroscopy (GFAAS) parameters for arsenic determination in water. By leveraging chemometric tools within the instrument software, the study simplifies method development and ensures adherence to international standards such as ISO 15586:2003 and U.S. EPA Method 200.9.

Methodology and Instrumentation

A transverse Zeeman background-corrected Agilent 240Z Graphite Furnace AAS system was employed. Key methodological steps and components include:

• Graphite furnace platform: Omega pyrolytic tube with Constant Temperature Zone design and Stabilized Temperature Platform Furnace concept
• Autosampler: Agilent PSD 120 Programmable Sample Dispenser
• Background correction: Transverse Zeeman effect for matrix interference removal
• Wavelength and optics: 193.7 nm arsenic lamp, 0.5 nm slit width, peak area mode
• Modifier mix: Pd(NO₃)₂ and Mg(NO₃)₂ to stabilize arsenic signal during ashing and atomization
• Inert gas: High-purity argon (99.99%)
• Parameter optimization: Integrated Tube-CAM camera for dry-step monitoring and Surface Response Methodology (SRM) chemometric tool to determine ideal ash and atomize temperatures

Main Results and Discussion

The chemometric optimization yielded consistent conditions for both standard and spiked samples, confirming the modifier composition’s suitability. Key performance metrics are:

• Characteristic concentration: 0.58 µg/L (peak area)
• Characteristic mass: 18.6 pg (peak area)
• Method detection limit (20 µL sample): 0.26 µg/L
• Validated quantification limit (20 µL sample): 1.0 µg/L
• Recovery for NIST 1640a reference material: 100.4%
• Recovery for bottled water spiked at 10 µg/L: 102.4%

These results exceed regulatory requirements, demonstrating both high sensitivity and accuracy.

Benefits and Practical Applications

The intelligent optimization workflow reduces manual trial-and-error during method setup, ensuring rapid deployment in routine laboratory environments. The combination of Zeeman background correction and stabilizing modifiers offers robust performance across diverse water matrices. Operational advantages include reduced argon consumption, extended graphite tube life, and simplified parameter adjustments via the SRM wizard.

Future Trends and Applications

• Integration of advanced chemometric algorithms for multi-element optimization and real-time quality control
• Expansion toward speciation analysis to differentiate inorganic and organic arsenic species
• Miniaturized, field-deployable GFAAS systems for on-site environmental monitoring
• Enhanced software connectivity with laboratory information management systems (LIMS) for automated data handling and regulatory reporting

Conclusion

The Agilent 240Z GFAAS platform, equipped with intelligent optimization features, delivers a cost-effective, high-performance solution for trace arsenic analysis in water. Automated ashing and atomization parameter selection, combined with advanced background correction and sample handling, ensures compliance with global drinking water standards and facilitates routine monitoring tasks.

References

• World Health Organization. Arsenic in Drinking-water. WHO/SDE/WSH/03.04/75/Rev/1 (2011).
• Agilent Technologies. Optimizing GFAAS ashing and atomizing temperatures using Surface Response Methodology. Publication number 5991-9156EN.