Quantitative Analysis of Tin (Sn) in Plastics by EDXRF

Significance of the Topic

The growing regulatory focus on organotin compounds positions tin (Sn) alongside established RoHS elements in electronic and plastic materials. Reliable detection and quantitation of Sn at trace levels are essential for compliance screening in manufacturing, quality control, and environmental monitoring.

Objectives and Overview of the Study

This study evaluates the performance of bench-top energy-dispersive X-ray fluorescence (EDXRF) instruments for ppm-level quantitation of Sn in polyethylene resin standards and practical plastic samples. It aims to integrate Sn into existing rapid screening workflows for RoHS elements without extending analysis time.

Methodology and Instrumentation

An internal-standard-corrected calibration curve was constructed using four PE resin standards spiked with Sn at 0, 310, 700, and 1100 ppm. Ten replicate measurements of the 700 ppm standard assessed repeatability. A real-world plastic component was screened for seven regulated elements (Cd, Pb, Cr, Hg, Br, Cl, Sn) under revised RoHS conditions.

• Instrument models: EDX-LE and EDX-GP (720)
• X-ray tube: Rh target, 50 kV
• Detector: Si-PIN (EDX-LE) or Si(Li) (EDX-GP)
• Primary filter: #1
• Collimator diameter: 10 mm
• Atmosphere: Air
• Integration time: 100 s, dead time ~40%

Main Results and Discussion

Calibration curves for Sn Kα exhibited linear response across 0–1100 ppm with accuracy of 1.4% (EDX-LE) and 1.0% (EDX-GP). Limits of detection were determined at 7.5 ppm and 8.2 ppm, respectively. Repeatability tests yielded coefficients of variation below 2.0%. In a plastic sample screening, Sn was quantified at 290 ppm, producing an “OK” result under the threshold of 700 ppm.

Benefits and Practical Applications of the Method

By leveraging existing RoHS analytical settings for Cd, EDXRF permits seamless addition of Sn quantitation without lengthening analysis cycles. This capability supports rapid compliance screening of plastic parts in electronics, automotive, and industrial sectors.

Future Trends and Applications

With anticipated inclusion of tin in restricted substance lists, demand for robust, high-throughput Sn screening will grow. Advances in detector technology and spectrum deconvolution are expected to further reduce detection limits and improve analytical precision. Automated sample handling and data integration will enhance lab productivity.

Conclusion

Bench-top EDXRF systems equipped with internal-standard calibration effectively quantify Sn at ppm levels in plastics, matching the throughput of conventional RoHS analyses. This approach enables straightforward incorporation of tin screening into established workflows, ensuring regulatory compliance without additional instrumentation or extended run times.