Fast and robust assessment of water quality using ICP-OES

Significance of the topic

Trace metal analysis in water is critical to public health and environmental protection. Even trace levels of elements such as lead, arsenic, and cadmium pose risks to human and ecological systems when present in drinking water or natural bodies of water. Regulatory frameworks worldwide have adopted standardized methods to ensure reliable monitoring of these contaminants. The DIN EN ISO 11885:2009 protocol uses ICP-OES to quantify multiple elements in a rapid and precise manner, streamlining the quality control of surface, drinking, and wastewater matrices.

Objectives and overview of the study

This study aimed to assess the performance of the Thermo Scientific iCAP PRO Series ICP-OES instrument for multi-element water analysis under the criteria defined in DIN EN ISO 11885:2009. By evaluating sensitivity, linearity, accuracy, and long-term stability, the research demonstrates how fast, reproducible assays can be conducted across diverse water samples, including tap, river, pond, and simulated wastewater. The use of two different instruments and fresh measurement days verified robustness and inter-laboratory consistency.

Methodology

Study design included calibration curve generation, quality control, and sample preparation:

• Calibration solutions spanned 0–1,000 µg/L for trace elements and up to 10,000 µg/L for major elements in 2% nitric acid.
• Internal standard (yttrium) was added to all calibrators and samples to correct matrix and instrumental drifts.
• Three certified reference materials (CRMs) were used as quality controls at 200 µg/L and matrix-relevant concentrations after dilution.
• Water samples (tap, river, pond) were filtered (45 µm) or microwave-digested for particulates following the standard protocol, then acidified to 2% v/v HNO₃.
• Spike recovery tests were performed at 10–100 times the detection limit to verify accuracy.

Instrumentation used

The analytical platform comprised:

• Thermo Scientific iCAP PRO XP ICP-OES Duo with axial and radial viewing capability.
• Standard sample introduction kit: concentric glass nebulizer, glass cyclonic spray chamber, quartz torch.
• Teledyne CETAC ASX-560 autosampler for unattended operation.
• For enhanced sensitivity tests, a U5000AT+ ultrasonic nebulizer with built-in spray chamber was employed.
• Instrument settings optimized for plasma gas flows, RF power, uptake times, and exposure to cover the full analyte range within 2 min 20 s per sample.

Main results and discussion

Key performance indicators demonstrated full compliance and often exceeded the DIN EN ISO requirements:

• Detection limits (XLD) for most elements were in the low single-digit µg/L range; quantification limits (XLQ) remained below method thresholds.
• Linearity across three to five calibration levels achieved R² > 0.9997 for all analytes up to 1,000 µg/L and extended to 10,000 µg/L for major elements in radial mode.
• Spike recovery in river water and wastewater matrices fell within ±15% for most analytes, meeting the ±20% criterion.
• Internal standard recoveries remained between 80% and 110% during 8-hour stability tests, indicating negligible matrix effects.
• Long-term measurements on three instruments in two laboratories produced consistent CRMs and sample recoveries within ±20% over 8 hours.
• Application of the ultrasonic nebulizer yielded 3–15× lower detection limits for key contaminants (e.g., As, Cd, Pb), supporting ultra-trace analysis.

Benefits and practical applications

The validated method provides the following practical advantages:

• High-throughput screening: full multi-element assay in under 3 minutes per sample.
• Versatility: applicable to drinking, surface, and wastewater matrices with minimal reconfiguration.
• Robust data quality: stringent QC and internal standardization ensure reproducible measurements.
• Scalability: additional sensitivity achieved when needed via ultrasonic nebulization.
• Regulatory compliance: meets or exceeds DIN EN ISO 11885:2009 and related international standards.

Future trends and potential applications

Continued advancements in ICP-OES instrumentation and sample introduction will further elevate capabilities in environmental monitoring:

• Integration of high-efficiency nebulizers and matrix removal devices for sub-µg/L detection in complex matrices.
• Automation and remote operation to handle large sample volumes in regulatory and industrial laboratories.
• Enhanced plasma designs and detector technologies for improved spectral resolution and reduced interferences.
• Data-driven workflows employing advanced software for real-time QA/QC, trend analysis, and reporting.
• Adaptation to emerging contaminants such as PFAS and nanoparticles within water quality frameworks.

Conclusion

The Thermo Scientific iCAP PRO Series ICP-OES platform delivers a powerful solution for water quality assessment under the DIN EN ISO 11885:2009 framework. It combines rapid analysis, robust performance, and flexible sensitivity to support environmental, drinking, and industrial applications. The method’s demonstrated accuracy, precision, and reproducibility underline its value in meeting stringent regulatory requirements and safeguarding public health.

Reference

DIN EN ISO 11885:2009—Water quality—Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES).