NEMC: Overcoming interferences in challenging sample matrices using ICP-OES

Significance of the Topic

Inductively coupled plasma optical emission spectrometry (ICP-OES) is essential for accurate multi-element analysis in environmental samples such as waters, soils, sludges and sediments. Spectral interferences arising from complex matrices challenge both detection limits and data integrity, necessitating robust correction strategies to meet regulatory standards.

Aims and Overview

This study evaluates the performance of the Thermo Scientific iCAP PRO Series ICP-OES, specifically the iCAP PRO XP ICP-OES Duo system, for the determination of trace elements in environmental matrices following US EPA Method 6010D (SW-846). The goal is to demonstrate sensitivity, accuracy, precision and long-term stability in the presence of challenging interferences.

Methodology and Instrumentation

• Sample preparation: Acid digestion of 20 water samples and 12 soil samples using EPA Methods 3010A, 3050B (hot-plate digestion) and Methods 3015A, 3051A (microwave-assisted digestion with Milestone ETHOS EZ SK10).
• Instrumentation: Thermo Scientific iCAP PRO XP ICP-OES Duo equipped with ASXpress PLUS rapid introduction, CID detection, dual axial and radial viewing, and Qtegra ISDS software featuring an automated inter-element correction (IEC) workflow.
• Calibration and quality control: Four-point calibration curves in 2% HNO₃; yttrium internal standard; individual and mixed spectral-interference check solutions; initial calibration verification and ongoing check standards; verification with NIST SRM 2781 (domestic sludge) and SRM 2709a (San Joaquin soil).

Main Results and Discussion

• Detection limits in typical laboratory conditions ranged from sub-ppb to low ppb for over 30 elements in both axial and radial viewing modes.
• IEC effectively identified and corrected spectral overlaps automatically across the full sample batch, applying concentration-based corrections inline for all data.
• Recovery of target elements in SRM 2781 and SRM 2709a fell within ±10% of certified values, confirming method accuracy.
• Long-term stability was demonstrated over 15 hours and more than 500 consecutive samples, with continuing calibration verification (CCV) recoveries within ±10% and stable internal standard recoveries, indicating no matrix carryover or signal drift.

Benefits and Practical Applications

• High analytical sensitivity and robust automated interference correction enable reliable trace analysis in complex environmental matrices.
• Rapid throughput (~1.5 minutes per sample) with simultaneous axial and radial acquisition enhances laboratory efficiency.
• Integrated flagging, IEC and reporting tools simplify compliance with EPA 6010D and other regulatory protocols.

Future Trends and Opportunities

Advances in software-driven correction algorithms and enhanced system stability are expected to broaden the scope of ICP-OES in environmental monitoring, process control and emerging applications such as nanoparticle characterization. Integration with automated sample preparation and advanced data analytics will further improve throughput, reproducibility and decision-making capabilities.

Conclusion

The Thermo Scientific iCAP PRO XP ICP-OES Duo system exceeds EPA Method 6010D requirements, delivering high sensitivity, precise interference correction and long-term stability for challenging environmental sample analysis.

References

• US EPA. July 2018. Method 6010D (SW-846 Update VI): “Inductively Coupled Plasma–Optical Emission Spectrometry,” Revision 6.
• Thermo Fisher Scientific. Application Note 74146: Fast, accurate, and robust analysis of environmental samples according to US EPA Method 6010D.