Quantitative Analysis of Antimony (Sb) in Plastics by EDXRF

Importance of the Topic

Antimony compounds are widely used as flame-retardant promoters in plastics, and recent RoHS regulations and corporate halogen-free initiatives require reliable quantification of Sb at the ppm level alongside other restricted elements. Rapid, accurate screening and quantitative analysis are essential for compliance, quality assurance, and environmental protection in electronics manufacturing and polymer processing.

Study Objectives and Overview

This study evaluates the sensitivity, accuracy, and throughput of commercially available antimony-spiked polyethylene (PE) standards using the Shimadzu EDX-720/GP energy dispersive X-ray fluorescence system. Key aims include establishing an internal-standard-corrected calibration curve for Sb, determining detection limits, assessing repeatability, demonstrating simultaneous multi-element analysis, and illustrating a rapid screening workflow for compliance judgments (OK/Gray/NG).

Methodology

An internal-standard-corrected calibration approach was employed, using four polyethylene standards (0, 310, 630, 1100 ppm Sb). X-ray fluorescence intensities (NET/BG ratio) were measured under fixed conditions: Rh target tube at 50 kV, auto current, #1 primary filter, 10 mm collimator, air atmosphere, Si(Li) detector, and 100 s integration time. Calibration curves were fitted near the origin to minimize background interference and theoretical detection limits were calculated from statistical criteria.

Used Instrumentation

• EDX-720 and EDX-GP energy dispersive X-ray fluorescence spectrometers
• Rh target X-ray tube, Si(Li) detector
• Working-curve analytical group for Sb(Kα)
• Primary filter #1, 10 mm collimator

Main Results and Discussion

The internal-standard-corrected calibration for Sb exhibited excellent linearity, delivering 0.8 ppm accuracy and a theoretical detection limit of 9.8 ppm with 100 s integration. Repeatability tests on the 630 ppm standard (n=10) yielded an average of 630.9 ppm, standard deviation 14.0 ppm, and coefficient of variation 2.2 %. Quantitative analysis of an unknown plastic fragment simultaneously measured Sb, Cd, Pb, Cr, Hg, Br, and Cl without extending total analysis time. A rapid screening protocol on the EDX-GP completed seven-element judgments in approximately two minutes, with Sb well within a 500 ppm threshold.

Benefits and Practical Applications of the Method

• Ppm-level sensitivity for Sb matching that of other RoHS-regulated heavy metals
• High accuracy and precision through internal-standard correction
• Simultaneous multi-element analysis without throughput penalty
• Fast screening decisions (OK/Gray/NG) for production and QA/QC
• Easy addition of Sb compliance to existing workflows

Future Trends and Potential Applications

Advancements in detector technology and miniaturized XRF instrumentation will drive lower detection limits and field-deployable screening for circular economy initiatives. Automation and software algorithms may enable real-time process control. Expansion to diverse polymer matrices and complex composites will broaden applications in environmental monitoring, recycling, and materials certification.

Conclusion

This work demonstrates that Shimadzu EDX-720/GP systems can deliver reliable, high-throughput quantitative analysis of antimony in plastics at the ppm level, fulfilling regulatory requirements without impacting cycle times. The approach supports both detailed compliance testing and rapid on-line screening, offering an efficient solution for electronics manufacturers, material suppliers, and environmental laboratories.

References

1. JPCA-ES02: Halogen-free copper-clad laminates for printed wiring boards – Paper base, phenolic resin, Japan Electronics Packaging Circuits Association.
2. IEC 61249-2-21.
3. Shimadzu Application News No. X222, X235.
4. Shimadzu Application News No. X231: Equation for Calculating Lower Limit of Detection.
5. Shimadzu Application News No. X224.