Robust analysis of REE in electronic waste

Significance of the Topic

This application note addresses the growing challenge of electronic waste (e-waste) and highlights the importance of accurately quantifying rare earth elements (REEs) and other valuable metals in discarded mobile phones. As demand for REEs continues to rise across industries—from permanent magnets and glass production to medical imaging—the recovery and responsible management of these elements from WEEE (Waste Electrical and Electronic Equipment) is critical for both economic and environmental sustainability.

Objectives and Study Overview

The primary aim of the study was to evaluate the performance of the Thermo Scientific™ iCAP™ PRO Series ICP-OES in axial mode for fast, robust, and sensitive analysis of trace and ultra-trace REEs as well as base, precious, and toxic metals in various components of mobile phone waste. Components examined included TFT screens, printed circuit boards (PCBs), and speaker magnets.

Methodology and Instrumentation

A streamlined sample preparation protocol was applied:

• Grinding of TFT screens and PCBs; whole‐digestion of speaker magnets.
• Overnight acid digestion using a 1:1 HCl:HNO₃ mixture or aqua regia for magnets.
• Filtration and final acid concentration of 10% TraceMetal™ grade HCl/HNO₃.
• Calibration standards prepared in matching acid matrix using certified multi-element and single-element solutions.

The analytical setup comprised:

Instrumentation Used

• Thermo Scientific™ iCAP™ PRO XP Duo ICP-OES operating in axial viewing mode.
• Glass cyclonic spray chamber, standard glass nebulizer, 2 mm quartz center tube, and quartz Duo torch.
• Teledyne™ CETAC™ ASX-560 autosampler for automated sample introduction.
• Qtegra™ ISDS Software for data acquisition, processing, interference prediction, and reporting.

Main Results and Discussion

• Linearity: Correlation coefficients (R²) exceeded 0.9999 over calibration ranges of 1–10,000 µg·L⁻¹ for REEs and 1–100,000 µg·L⁻¹ for base/precious metals.
• Detection Limits: Instrument detection limits (IDLs) were in the low ppb (single-digit µg·L⁻¹) range for all analytes.
• Method Detection Limits (MDLs): Sample-specific MDLs, accounting for dilution factors, ranged from low ppb to tens of µg·g⁻¹ depending on sample matrix and element concentration.
• Interference Management: The Qtegra™ ISDS interference prediction and correction tools effectively identified and corrected spectral overlaps (e.g., Tb on Gd) ensuring accurate quantification.
• Accuracy and Precision: Spike recoveries for laboratory‐simulated and magnet samples were within ±15%, demonstrating method accuracy. Long-term stability tests over 6-hour runs showed analyte recovery remaining between 80% and 120%, confirming robustness.
• Throughput: A total analysis time of under 2 minutes per sample (including uptake, three replicates, and rinse) enables high sample throughput suitable for demanding laboratory workflows.

Benefits and Practical Applications of the Method

• Enables multi-element screening of e-waste components at trace and major concentration levels with a single instrument.
• Offers cost-effective alternative to ICP-MS for many applications while maintaining competitive sensitivity and dynamic range.
• Simplified sample preparation protocol and automated introduction reduce analyst workload and contamination risk.
• High throughput and robust operation support contract laboratories and high-volume testing environments.

Future Trends and Potential Applications

Advances in ICP-OES technology and software intelligence will continue to expand the capability to:

• Implement real-time spectral interference correction for even more complex matrices.
• Integrate automated sample digestion and dilution systems for end-to-end workflow efficiency.
• Couple with separation techniques (e.g., ion chromatography) for speciation analysis of REEs and other critical metals.
• Apply to broader recycling streams, including batteries, magnets, and industrial catalysts, to support circular economy initiatives.

Conclusion

The Thermo Scientific™ iCAP™ PRO Series ICP-OES platform in axial mode delivers high sensitivity, wide dynamic range, and reliable performance for the analysis of REEs and other metals in electronic waste. Its rapid analysis time, robust interference management, and user-friendly software make it an effective tool for laboratories focused on e-waste recycling, environmental monitoring, and quality control.

Reference

1. Zawisza B., Pytlakowska K., Feist B., Polowniak M., Kita M., Sitko R. Determination of rare earth elements by spectroscopic techniques: a review. Journal of Analytical Atomic Spectrometry, 2011, 26, 2373–2390.