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

Importance of the Topic

The rapid and reliable measurement of trace metals and their speciated forms is critical for environmental monitoring, regulatory compliance and material safety. Techniques such as inductively coupled plasma mass spectrometry (ICP-MS), enhanced by collision/reaction cells and chromatographic coupling, address challenges of sensitivity, matrix interference and species stability. These capabilities support directives like RoHS/ELV, drinking-water standards, mercury speciation in water and soil, and chromium toxicity assessment.

Objectives and Study Overview

This compilation of applications from the Agilent ICP-MS Journal Issue 23 (May 2005) presents four core studies:

• Quantification of RoHS/ELV elements (Cd, Pb, Hg, Cr6+) in plastics using a 7500c ICP-MS.
• Reduction of matrix oxide interferences with Octopole Reaction System (ORS) in He collision mode on the 7500ce.
• Speciation of methylmercury, ethyl-mercury and inorganic Hg in water and soil by HPLC-ICP-MS.
• Multi-element and speciated chromium determination in natural waters via ion chromatography coupled to ICP-MS.

Methodology

The studies employ high-efficiency plasma conditions, low-flow nebulization and cooled spray chambers to minimize oxide formation (CeO/Ce <0.5%). The ORS in He mode with kinetic energy discrimination (KED) further attenuates residual MO+ interferences. Chromatographic coupling involves:

• HPLC-ICP-MS with ZORBAX Eclipse XDB-C18 for mercury speciation, using 20–100 µL injection loops.
• Ion chromatography pump for chromium speciation, with EDTA mobile phase at pH 7 and sample stabilization at 40 °C.

Instrumentation Used

• Agilent 7500c and 7500ce ICP-MS with ORS collision cell.
• Agilent 1100 HPLC and LC-ICP-MS connection kit.
• Metrohm 818 IC pump and ZORBAX Eclipse XDB-C18 column.
• Integrated Sample Introduction System (ISIS) for automated loop filling.

Main Results and Discussion

• RoHS/ELV plastics analysis achieved z-scores within ±1 in an ISO/IEC proficiency test for Cd and Pb, matching EN1122 and EPA 3052 methods.
• ORS He mode reduced CeO/Ce ratio from ~0.4% to 0.07%, enabling interference-free measurement of rare earths and other high-matrix elements.
• HPLC-ICP-MS speciation of MeHg, EtHg and Hg2+ delivered detection limits <10 ng/L in water and recoveries of 90–110% in 3% NaCl and 80–120% in soil extracts.
• 7500ce ICP-MS in He cell gas mode achieved arsenic MDLs ~20 ppt, making it the only approved multi-element method for drinking-water compliance when EPA 200.7 is withdrawn.
• Cr(III) and Cr(VI) speciation by IC-ICP-MS yielded detection limits <20 ng/L and spike recoveries of 103–105% in high-matrix mineral water.

Benefits and Practical Applications

These methods provide:

• Simultaneous multi-element analysis with minimal sample preparation and no need for complex desolvation or reactive gases.
• Robust quantification in diverse matrices: plastics, drinking water, seawater, soils and natural waters.
• Regulatory compliance for RoHS/ELV, drinking-water standards, mercury exposure limits and chromium toxicity assessments.

Future Trends and Applications

Advances in collision/reaction cell design, software features like pre-emptive rinsing, and expanded speciation protocols will drive deeper insights into trace element behavior. Integration with high-throughput platforms and broader user collaboration through forums and success-story sharing will further enhance method development and application scope.

Conclusion

The Agilent 7500 series ICP-MS, equipped with ORS in He collision mode and chromatographic interfaces, delivers ultra-low detection limits, robust interference removal and reliable species preservation. This suite of techniques meets emerging regulatory demands and supports comprehensive environmental, industrial and research applications.

References

• BSEN1122:2001 Plastics – determination of cadmium – Wet decomposition method.
• Results Proficiency Test Cadmium and Lead in Plastics, Institute for Interlaboratory Studies, October 2004.
• JEITA JGPSSI Guideline for Standardization of Material Declaration, Japan Electronics and Information Technology Association.
• EPA Method 200.8, Determination of Trace Elements in Drinking Water by ICP-MS.
• World Health Organization, Guidelines for Drinking-water Quality (Arsenic).