Screening Analysis of Trace Heavy Metals in Powdered Milk

Significance of the Topic

The presence of trace heavy metals in powdered milk poses a significant health risk, especially for infants and young children. Rapid and reliable screening methods are essential for quality control and regulatory compliance. Energy dispersive X-ray fluorescence spectrometry (EDXRF) offers a non-destructive approach that can streamline testing workflows by reducing sample preparation time and increasing throughput.

Study Objectives and Overview

This study demonstrates the application of the Shimadzu ALTRACE EDXRF system for screening trace levels of arsenic, cadmium, tin, mercury and lead in powdered milk. The goals are to compare its sensitivity and speed with the conventional EDX-7000 instrument, to establish calibration and detection limits, and to validate the method using standard reference samples.

Methodology and Instrumentation

Sample Preparation

• Samples were placed in polypropylene film-lined containers and compressed to form uniform pellets.
• No chemical reagents or complex digestion steps were required.

Instrument and Analysis Conditions

• Instrument: Shimadzu ALTRACE EDXRF
• Detector: Silicon drift detector (SDD)
• X-ray tube target: Rhodium
• Tube voltage: 50 kV for As, Hg, Pb; 65 kV for Cd, Sn
• Current: Automatic adjustment
• Primary filters: Filter #5 for As, Hg, Pb; Filter #1 for Cd, Sn
• Atmosphere: Air
• Integration time: 600 seconds per channel
• Dead time: Up to 40%

Main Results and Discussion

Calibration curves for all five elements showed accuracy better than 0.12 ppm, with root-mean-square deviations below this value. Limits of detection (LOD) achieved with ALTRACE were 0.029 ppm (As), 0.069 ppm (Hg), 0.059 ppm (Pb), 0.075 ppm (Cd) and 0.131 ppm (Sn), matching or exceeding those of the EDX-7000 while using only one-tenth of the measurement time. Comparative fluorescence spectra highlighted clear peak separation at 1 ppm for arsenic and cadmium with ALTRACE, whereas the EDX-7000 failed to resolve cadmium at that level. A screening test on a 1 ppm standard sample confirmed that ALTRACE can reliably determine concentrations within regulatory thresholds for powdered milk.

Benefits and Practical Applications

• Rapid throughput: Analysis time reduced by a factor of ten compared to conventional EDXRF.
• Minimal sample preparation: Direct measurement of powder without digestion.
• High sensitivity and repeatability: Low detection limits and consistent results.
• Automation potential: Capability to process up to 48 samples sequentially, supporting large-scale quality control.

Future Trends and Opportunities

Emerging trends include integrating advanced data analytics and machine learning to improve matrix effect corrections, development of portable EDXRF systems for onsite food inspection, and expansion of screening protocols to include additional contaminants. Ongoing enhancements in detector technology and X-ray sources are expected to further lower detection limits and reduce measurement times.

Conclusion

The ALTRACE EDXRF system provides a robust solution for rapid screening of trace heavy metals in powdered milk, combining high sensitivity, simplified sample preparation and significant time savings. It enables reliable compliance verification and supports efficient quality assurance in the dairy industry.

References

• Shimadzu Corporation, Application News No. X260: Screening Analysis of Trace Heavy Elements in Powdered Milk by EDXRF, November 2024.
• Japan Baby Food Council, Voluntary Standards for Heavy Metal Tolerances in Baby Food, Tokyo.