EDXRF Analysis of PM2.5 (Particle Matter)

Significance of the Topic

Fine particulate matter (PM2.5) presents significant health and environmental risks. Accurate, non-destructive multi-element analysis of PM2.5 is essential for regulatory compliance, pollution source identification, and exposure assessment.

Objectives and Study Overview

This work evaluates energy-dispersive X-ray fluorescence (EDXRF) for rapid analysis of PM2.5 collected on polycarbonate membrane filters. Using NIST SRM2783 as a reference, the study compares qualitative and quantitative results without chemical pretreatment, employing fundamental parameter (FP) quantification.

Methodology and Instrumentation

Sample Preparation and Placement:

• Method 1: Expose sample on 13 mm diameter window between two 4 µm Prolene films to maximize light-element sensitivity.
• Method 2: Cover entire stage with Prolene film to prevent particle loss, reducing sensitivity for elements like Na and Mg by ~50%.

Instrumentation and Analytical Conditions:

• EDX-720 spectrometer with Rh target X-ray tube: 15 kV for Na–Cl, 50 kV for K–U; tube current 1000 µA (auto).
• Primary filters: none for Na–P, auto-select filters for heavier elements.
• Vacuum atmosphere, 10 mm measurement diameter, 600 s integration per channel, max dead time 40%.

Main Results and Discussion

Qualitative Analysis:
Elemental peaks from Na to U were detected after blank subtraction. Rh and Si escape peak interferences near NaKα were identified and corrected to confirm Na detection.

Quantitative Analysis:
FP method produced element recoveries ranging 50–85% for light elements (Na, Mg, Al, Si) and 10–30% error for K, Ca, and heavier elements. Sulfur showed a two-fold enhancement due to blank filter contributions.

Theoretical Detection Limits:

• Na: 60 ng/cm²; Mg: 25; Al & Si: 9.4; S: 5.7; K: 4.8; Ca: 3.8; Ti: 2.9; Cr: 1.9; Mn: 2.5; Fe: 2.7; Ni: 1.9; Cu: 1.7; Zn: 3.1; Rb: 1.2; Ba: 6.0; Pb: 8.2.

Benefits and Practical Applications

This EDXRF approach offers:

• Rapid, non-destructive multi-element screening without chemical digestion.
• Sufficient accuracy for routine environmental monitoring and regulatory compliance.
• Capability to identify and correct spectral interferences such as escape peaks.

Future Trends and Potential Applications

Improvements in detector resolution and data processing will lower detection limits and enhance light-element sensitivity. Integration with automated samplers and in-field EDXRF instruments may enable near-real-time air quality monitoring and source apportionment.

Conclusion

EDXRF analysis of PM2.5 on membrane filters using the Shimadzu EDX-720 delivers reliable elemental quantification with minimal sample preparation. The FP method combined with blank correction yields acceptable accuracy for a wide range of elements, supporting its use in environmental and regulatory applications.

Reference

• Shimadzu Application Note LAAN-A-XR-E018A: EDXRF Analysis of PM2.5.
• NIST SRM2783 Air Particulate on Filter Media.