Agilent ICP-MS Journal (May 2005 – Issue 23)

Importance of Topic

Analysis of trace heavy metals and species in various matrices is critical for regulatory compliance and environmental protection. Advanced ICP-MS methods address interference challenges and enhance sensitivity for directives such as RoHS, ELV and drinking water standards.

Objectives and Overview

This summary covers methods to measure restricted heavy metals for RoHS and ELV compliance, use of collision cell technology to reduce matrix oxides, speciation of mercury by hyphenated HPLC-ICP-MS, multi-element arsenic determination by ICP-MS, and ion chromatographic separation of chromium species in natural waters.

Methodology

• Direct quantification of Cd, Pb, Cr and Hg in polymer matrices using Agilent 7500 series ICP-MS with acid and microwave digestion following BSEN1122 and EPA3052 protocols, validated via international proficiency testing.
• Reduction of metal oxide interferences through an octopole reaction system in helium mode with kinetic energy discrimination, lowering CeO ratios to below 0.1 percent.
• HPLC-ICP-MS coupling for simultaneous analysis of methyl mercury, ethyl mercury and inorganic mercury employing an Agilent 1100 LC, 7500a ICP-MS and dilute acid extraction.
• Ion chromatographic separation of CrIII and CrVI using EDTA complexation on a Metrohm pump with parallel detection by 7500ce ORS ICP-MS in hydrogen cell gas mode to remove ArC and ClOH interferences.
• Helium collision mode in the 7500ce ICP-MS for arsenic analysis in drinking water achieving detection limits near 20 ppt without reactive gases or complex desolvation.

Instrumentation

• Agilent 7500c, 7500ce and 7500a ICP-MS systems with Octopole Reaction System and Helium or Hydrogen cell gas options.
• Agilent 1100 high performance liquid chromatograph for mercury speciation.
• Metrohm 818 ion chromatography pump for mobile phase delivery in chromium speciation.
• Microwave digestion units and automated sampling systems for reproducible sample preparation.

Main Results and Discussion

• ICP-MS methods reliably quantified restricted metals at thresholds of 100 to 1000 mg/kg for RoHS/ELV materials with z-scores within ±1 in proficiency tests.
• ORS helium mode reduced CeO interference to 0.07 percent, enabling accurate high-mass rare earth element measurements without desolvation devices.
• HPLC-ICP-MS speciation exhibited calibration linearity over four orders of magnitude, detection limits below 10 ng/L, and recoveries between 90 and 110 percent in high matrix water and soil extracts.
• The 7500ce ICP-MS achieved arsenic detection limits near 20 ppt in drinking water, surpassing revised regulatory requirements after withdrawal of ICP-OES methods.
• Chromium speciation delivered detection limits under 20 ng/L with spike recoveries around 100 percent in high hardness mineral waters.

Benefits and Practical Applications

• Streamlined multi-element and speciation workflows support electronic, automotive and environmental monitoring.
• Collision cell technology simplifies interference removal and enhances data quality without complex reagents.
• Hyphenated techniques provide simultaneous quantification of toxic and essential metal forms in diverse sample types.
• Integrated sample introduction software and preemptive rinsing improve throughput and reproducibility.

Future Trends and Opportunities

Broad adoption of collision cell ICP-MS for compliance, speciation and complex matrix analysis will continue. Further advances in instrument design, software integration and coupling methods will lower detection limits and expand the range of analytes. Ongoing development of validated protocols and reference materials, coupled with increased community sharing through success stories and user forums, will drive innovation in analytical chemistry.

Conclusion

Advanced ICP-MS approaches integrating robust plasma design, collision cell modes and hyphenated separation techniques deliver reliable trace metal and speciation analyses across challenging matrices, meeting stringent regulatory requirements and enhancing laboratory efficiency.

Reference

• BSEN1122:2001 Plastics determination of cadmium by wet decomposition method
• ISO/IEC Guide 43 Proficiency Test Cadmium and Lead in Plastics October 2004
• JEITA Guideline for Standardization of Material Declaration JGPSSI
• EPA Method 3052 Microwave assisted acid digestion of siliceous and organically based matrices
• EPA 40 CFR 141 Method 200.8 Determination of dissolved elements by inductively coupled plasma mass spectrometry
• JECFA Provisional Tolerable Weekly Intake for methylmercury