Determination of Trace Impurities in High-Purity Copper by Sequential ICP-OES with Axial Viewing

Importance of the Topic

High-purity copper is widely used in electronics, aerospace and archaeological studies. Even trace levels of impurities can significantly alter mechanical, electrical and corrosion properties. Accurate control and quantification of these contaminants are therefore critical for product performance, regulatory compliance and material provenance investigations.

Study Goals and Overview

This work aimed to develop and validate a sequential ICP-OES method with axial plasma viewing for the determination of eight trace elements (As, Bi, Fe, Ni, Pb, Sb, Sn and Zn) in high-purity copper. The study compared results with certified reference materials and evaluated improvements in detection limits relative to radial viewing.

Methodology and Instrumentation

Copper samples were prepared by dissolving 0.5 g of high-purity chips in 1:1 HNO₃ and diluting to 2% (w/v) Cu. Matrix-matched standards were made from BDH stock solutions. Measurements were performed on an Agilent Liberty Series II ICP-OES with axial viewing, using a glass cyclonic spray chamber and concentric nebulizer. Key parameters: 1.2 kW RF power, 15 L/min plasma gas, 1.5 L/min auxiliary gas, 3 s integration time and three replicates.

Main Results and Discussion

The method achieved excellent agreement with certified values for both GBW 02113 and GBW 02114 reference materials, except for a low Fe value in GBW 02113. Axial viewing improved signal-to-background ratios, yielding detection limit enhancements of 2–3× on average and up to 8× for longer wavelengths compared to radial viewing. Detection limits in 2% Cu solutions ranged from 0.43 ppb (Fe 238.204 nm) to 10.7 ppb (Bi 190.178 nm).

Benefits and Practical Applications

• Enhanced sensitivity allows reliable quantification of sub-ppm impurities in copper products.
• Matrix-matched calibration ensures accuracy in complex copper matrices.
• Applicable to quality control in copper wire manufacture and archaeological bronze analysis.

Future Trends and Opportunities

Further improvements may include combining axial viewing with collision/reaction cell technology to reduce spectral overlaps, exploring alternative sample introduction systems for lower backgrounds and expanding the element scope. Integration with hyphenated techniques could facilitate simultaneous speciation and total element analysis.

Conclusion

The sequential ICP-OES method with axial viewing on the Agilent Liberty Series II provides robust, sensitive and accurate determination of trace impurities in high-purity copper. Detection limits are significantly improved over radial viewing, meeting stringent requirements for industrial and archaeological applications.

Used Instrumentation

• Agilent Liberty Series II ICP-OES with axial plasma viewing and AGM-2 argon purge accessory.
• Glass cyclonic spray chamber and Glass Expansion concentric nebulizer.
• Black-black sample tubing to minimize carry-over.

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