Arsenic in Natural Waters by Graphite Furnace Atomic Absorption using EPA Method 200.9.

Importance of the Topic

Arsenic is a naturally occurring element that poses significant health risks when present above regulatory limits in natural and drinking waters. Chronic exposure is linked to multiple cancers and systemic effects. The tightening of the US EPA standard to 10 µg/L underscores the need for sensitive and reliable analytical methods capable of measuring low arsenic levels in complex matrices.

Objectives and Overview of the Study

This application note demonstrates the use of Thermo Scientific iCE 3000 Series Atomic Absorption Spectrometers with Graphite Furnace Atomic Absorption Spectrometry (GFAAS) following EPA Method 200.9. It details method development, instrument optimization, performance qualification, and analyte recovery for arsenic in various natural and treated water matrices.

Methodology

The study applies EPA Method 200.9 protocols for trace element determination by stabilized temperature GFAAS in groundwater, surface water, and drinking water. Key steps include matrix modifier preparation (palladium/magnesium solution), sample acidification, calibration using segmented curve fitting, and optional standard additions for high‐matrix samples. Quality control follows method requirements: initial demonstration of performance, ongoing calibration blank checks, continuing instrument performance, laboratory fortified matrix spikes, and check standards. Method detection limit (MDL) and linear dynamic range (LDR) were established through replicate analyses of fortified blanks and calibration standards.

Used Instrumentation

• Thermo Scientific iCE 3000 Series Atomic Absorption Spectrometer with Zeeman background correction
• Graphite Furnace Autosampler
• Graphite Furnace TeleVision accessory for real-time cuvette imaging
• SOLAAR software for automated method development, optimization, and QC

Main Results and Discussion

The method achieved an MDL of 0.6 µg/L and a linear range up to 120 µg/L with 99 % calibration accuracy at 20 µg/L. Quality control samples showed recoveries of 96–102 % with RSD below 3 %. Laboratory fortified matrix spikes in natural and drinking waters recovered 79–100 %. Standard additions corrected matrix effects in high‐salinity samples. Analysis of NIST 1640 reference water yielded 94 % recovery with 4.6 % RSD.

Benefits and Practical Applications

• Meets EPA 200.9 requirements for regulatory compliance
• High sensitivity and low detection limits suitable for drinking water monitoring
• Automated optimization and QC streamline laboratory workflows
• Versatile across diverse matrices including high‐salinity and low‐analyte samples

Future Trends and Possibilities

Advances may include integration with alternative spectrometric techniques, further miniaturization of graphite furnaces, and enhanced software analytics for real‐time quality assurance. Portable GFAAS platforms could enable field-based arsenic monitoring.

Conclusion

The Thermo Scientific iCE 3000 GFAAS system provides a robust, compliant, and efficient solution for arsenic analysis in natural and drinking waters. Comprehensive method validation and QC procedures ensure reliable results at sub-ppb levels.

References

1. Thermo Scientific AN40849: Lead in Natural Waters by Graphite Furnace AAS using EPA Method 200.9.
2. Welz B; Schlemmer G; Mudakavi RJ. J Anal At Spectrom. 1992, 7, 1257: Palladium Nitrate–Magnesium Nitrate Modifier for ET AAS.