EDXRF Analysis of Chromium, Mercury, Bromine, Lead and Cadmium in Plastic Materials

Significance of the Topic

Energy dispersive X-ray fluorescence (EDXRF) is vital for rapid, nondestructive screening of hazardous elements in plastics, ensuring compliance with RoHS regulations and supporting environmental protection efforts.

Study Objectives and Overview

• Determine sensitivity (lower limits of detection) and repeatability of EDXRF measurements for Cr, Hg, Pb, Br, and Cd in PVC matrices.
• Use PVC samples spiked at known concentrations (calibrated by ICP/MS) to evaluate performance.

Methodology and Instrumentation

• Samples prepared with element concentrations ranging from 0 to 1200 ppm for Cr, Hg, Pb, Br and up to 300 ppm for Cd.
• Optimized measurement conditions: voltage 30–50 kV, current 190–1000 µA, measurement time 300 s, dead time 40%.
• Lower limits of detection calculated using a three‐sigma formula; Br‐Kα data corrected for overlap with Hg‐Lβ1.

Instrumentation Used

• Shimadzu EDX-720 energy dispersive XRF spectrometer with Rh target tube.
• Filters: Al for Cr; Filter #1 for Hg, Pb, Br; Filter #2 for Cd.
• Air atmosphere; 10 mm measurement diameter.

Main Results and Discussion

• Detection limits: 1.4 ppm for Br‐Kα up to 10.9 ppm for Cr‐Kα.
• Calibration curves showed linearity with accuracies of 30 ppm (Cr), 9.1 ppm (Hg), 23 ppm (Pb‐Lα), 26 ppm (Pb‐Lβ1), 13 ppm (Br), and 3.3 ppm (Cd).
• Repeatability tests (10 replicates) yielded practical CVs from 0.6% to 2.9%, consistent with theoretical values.

Benefits and Practical Applications

• Enables fast, nondestructive screening of plastics in electronics manufacturing and recycling.
• Supports quality assurance, regulatory compliance, and environmental monitoring.
• Eliminates lengthy sample preparation, suitable for diverse sample forms.

Future Trends and Applications

• Development of advanced detectors to further reduce detection limits.
• Portable XRF systems for on‐site compliance testing.
• Integration with chemometric algorithms for automated data interpretation.

Conclusion

The EDX-720 delivers reliable, high‐throughput analysis of Cr, Hg, Pb, Br, and Cd in PVC, meeting industry demands for speed, sensitivity, and nondestructive testing.

References