Analysis of nutrients in milk-based powders by EDXRF

Significance of the topic

Analyzing essential nutrients in fortified milk powders is critical for ensuring product quality, regulatory compliance and accurate nutritional labeling. Rapid multi-element assessment at or near the production line helps optimize manufacturing processes, reduce waste and maintain consistent batch performance.

Objectives and overview of the study

This work evaluates energy-dispersive X-ray fluorescence (EDXRF) with a silicon drift detector featuring a graphene window for quantifying ten key elements (Na, Mg, P, Cl, K, Ca, Mn, Fe, Cu and Zn) in milk-based powder matrices. The study demonstrates improved detection of light elements, establishes calibration models using in-house standards, validates analytical performance against ICP-OES and assesses long-term stability.

Methodology and instrumentation

Sample preparation involved pressing 6.0 ± 0.1 g of powder into 32 mm pellets without prior drying or grinding. A Thermo Scientific ARL QUANT’X EDXRF spectrometer equipped with a 50 W Rh/Ag end-window X-ray tube and a large-area SDD with a submicron graphene window was used. Three excitation conditions optimized element excitation:

• Low Za (4 kV, helium atmosphere, no filter, 180 s) for Na and Mg
• Low Zb (8 kV, helium, carbon thick filter, 60 s) for P, Cl, K and Ca
• Mid Zb (20 kV, air, silver medium filter, 180 s) for Mn, Fe, Cu and Zn

The graphene window enabled detection down to carbon, substantially enhancing Na and Mg sensitivity. Calibration employed 13 in-house standards referenced by ICP-OES, with spectrum fitting and optional normalization against scattered background to compensate matrix effects.

Main results and discussion

Calibration curves yielded correlation coefficients (R2) above 0.96 and low root mean square errors for all elements. Slope and intercept values closely approached ideal unity and zero, demonstrating strong agreement with reference data. Validation across 23 standards produced standard errors of prediction in line with industrial requirements. A 28-day stability study showed consistent results for high and low concentration elements, indicating minimal drift and reliable performance over time.

Benefits and practical applications

EDXRF with a graphene-window SDD offers rapid, non-destructive multi-element analysis with minimal sample preparation. Short measurement times and near-line deployment support real-time quality control in dairy processing. The method reduces turnaround, avoids complex inter-element corrections and enhances detection of traditionally challenging light elements.

Future trends and potential applications

Advancements may include automated sample handling, enhanced matrix correction algorithms and integration with process analytical technology systems for continuous monitoring. Expanding the approach to other complex food and feed matrices, and coupling with data analytics, will further improve process control and traceability.

Conclusion

The ARL QUANT’X EDXRF spectrometer with a graphene detector window provides a robust, efficient solution for monitoring critical nutrients in milk-based powders. Improved light element sensitivity, reliable calibration and long-term stability make it well suited for industrial quality assurance and regulatory compliance.