Agilent ICP-MS Journal (November 2014 – Issue 59)

Importance of the topic

Rapid, accurate elemental analysis is critical in environmental testing of complex matrices such as soil and sludges, and in quality control of high-purity rare earth oxides used in advanced materials. Techniques that combine high throughput, strong matrix tolerance, and interference removal are essential to meet regulatory requirements and industrial demands.

Objectives and overview

Two studies were presented. The first evaluated the Agilent 7900 ICP-MS with Ultra High Matrix Introduction (UHMI) and ISIS 3 discrete sampling for fast, EPA 6020A-compliant soil analysis. The second demonstrated direct measurement of trace rare earth element (REE) impurities in 500 ppm Nd₂O₃ using the Agilent 8800 Triple Quadrupole ICP-MS (ICP-QQQ) with MS/MS to eliminate Nd-derived interferences.

Methodology and instrumentation

In the soil study, a 7900 ICP-MS with nickel cones, glass concentric nebulizer, UHMI option and ISIS 3 discrete sampling (ISIS-DS) processed Certified Reference Materials and environmental sediments in 1/10 and 1/50 dilutions. A He collision cell mode was used for most elements, with no gas mode for low masses. In the REE study, an 8800 ICP-QQQ with High Matrix Introduction, quartz torch, MicroMist nebulizer and Peltier-cooled spray chamber was operated in five cell modes: no gas, He collision, O₂ mass-shift, NH₃ on-mass and NH₃ mass-shift. Calibration standards and internal standards were used to assess Background Equivalent Concentrations (BECs), spike recoveries and long-term stability.

Used instrumentation

• Agilent 7900 ICP-MS with UHMI option and ISIS 3 discrete sampling
• Agilent 8800 Triple Quadrupole ICP-MS with MS/MS reaction cell and HMI aerosol dilution

Main results and discussion

The 7900 ICP-MS analyzed 383 soil and sediment samples in 9 h 35 min (run-to-run <90 s), improving throughput by ~30% versus a 7700x with ISIS 2. Recoveries for 24 elements in two soil CRMs were 96–110%, with RSDs ≤3%. The system handled high-TDS digests without performance loss. In the REE study, O₂ mass-shift mode reduced NdO interferences and achieved BECs in the low ppt range for high-mass REEs. NH₃ mass-shift further improved sensitivity for Tb, and NH₃ on-mass mode enabled accurate Dy and Ho determination. Two-hour stability tests showed spike recoveries within 95–105% and signal RSDs <5%.

Benefits and practical applications

• High-speed, compliant soil screening in environmental and contract laboratories
• Accurate, direct impurity profiling of Nd₂O₃ for magnet and high-tech material production
• Reduced sample preparation and improved lab productivity through discrete sampling and MS/MS interference removal

Future trends and possibilities

Further developments may include automated online matrix correction, adaptive reaction cell gas switching, integration of triple quadrupole ICP-MS with high-resolution separation, and AI-driven method optimization to extend direct analysis to increasingly challenging matrices and ultra-trace detection.

Conclusion

The combination of UHMI aerosol dilution and ISIS 3 discrete sampling on the Agilent 7900 ICP-MS delivers rapid, robust soil analysis with full regulatory compliance. The Agilent 8800 ICP-QQQ with MS/MS offers powerful interference removal for direct REE impurity measurement in Nd₂O₃, achieving ppt-level detection and excellent stability. Together, these advances enhance throughput and data quality for environmental and materials applications.

References

• Agilent application note: Maximizing productivity for high matrix sample analysis using the Agilent 7900 ICP-MS with ISIS 3 discrete sampling system, 5991-5208EN
• Naoki Sugiyama and Glenn Woods, Direct measurement of trace rare earth elements (REEs) in high-purity REE oxide using the Agilent 8800 Triple Quadrupole ICP-MS with MS/MS mode, Agilent publication, 2012, 5991-0892EN