Rapid, interference-free analysis of water according to US EPA Method 200.7

Importance of the topic

Monitoring water quality for inorganic contaminants is essential to protect ecosystems and public health. Rapid, interference-free analysis according to EPA Method 200.7 provides reliable detection of major and trace elements in drinking, ground, surface, and wastewater.

Objectives and study overview

• Develop a fast, complete solution for multi-element water analysis using Thermo Scientific iCAP PRO Series ICP-OES Duo.
• Validate method accuracy, robustness, and sensitivity per US EPA Method 200.7.
• Demonstrate high sample throughput and effective spectral interference correction.

Methodology and instrumentation

Water samples were filtered, acidified, and calibrated following EPA Method 200.7 guidelines. A four-point calibration spanning target analytes was performed. Instrumentation details:

• Thermo Scientific iCAP PRO XP ICP-OES Duo operating in axial and radial viewing modes.
• CETAC ASX-560 autosampler with ASXPRESS plus rapid sampling accessory to reduce uptake and rinse times.
• Spray chamber: glass cyclonic; nebulizer: concentric glass; torch: quartz Enhanced Matrix Tolerance Duo.
• Operating parameters: RF power 1,150 W; gas flows: nebulizer 0.5 L/min, auxiliary 0.5 L/min, coolant 12.5 L/min; pump speed 45 rpm; replicates 3; exposure time 5 s (axial, radial).

Instrumentation used

• Thermo Scientific iCAP PRO XP ICP-OES Duo.
• Thermo Scientific Qtegra ISDS Software with concentration-based interelement correction.
• Teledyne CETAC ASX-560 autosampler and ASXPRESS plus rapid sample introduction accessory.

Main results and discussion

• Method detection limits (MDLs) ranged from 0.03 µg/L (Sr) to 37.7 µg/L (K), with linear dynamic ranges up to several thousand mg/L.
• Accuracy studies across diverse matrices (drinking, tap, river, groundwater, hard water) showed recoveries within ±15%, meeting EPA criteria.
• Instrument performance checks remained within ±10% over a 14-hour run, demonstrating stability.
• Yttrium internal standard recoveries were stable within ±15% throughout analysis, confirming robustness.
• Concentration-based interelement correction effectively removed spectral overlaps, yielding accurate recoveries (90–110%) in spiked mixed solutions.

Benefits and practical applications of the method

• High throughput: analysis time reduced to 57 seconds per sample, boosting lab productivity.
• Enhanced robustness allows analysis of complex matrices without frequent recalibrations.
• Automated IEC ensures reliable data in the presence of spectral interferences.
• Comprehensive QC features in Qtegra ISDS Software simplify compliance with regulatory standards.

Future trends and potential applications

• Integration with advanced autosamplers and AI-driven data processing for further throughput gains.
• Expansion to other matrices (soil, sludges, biological samples) with minimal method adaptation.
• Development of enhanced spectral deconvolution algorithms for ultra-trace analysis in challenging environments.
• Remote monitoring and real-time environmental surveillance using miniaturized ICP-OES platforms.

Conclusion

The optimized ICP-OES method using the iCAP PRO XP Duo and rapid sampling accessories meets EPA 200.7 performance criteria while drastically reducing analysis time. Automated interference correction and robust QC protocols ensure accurate, reliable multi-element water analysis suitable for high-throughput laboratories.

Reference

1. US EPA Method 200.7. Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled Plasma–Atomic Emission Spectrometry.
2. Thermo Fisher Scientific. iCAP PRO Series ICP-OES Product Brochure.
3. Thermo Fisher Scientific. Application Note AN44422: US EPA Method 200.7 using Thermo Scientific iCAP PRO XPS Duo ICP-OES.