Measurement of Heavy Metals (Cd, Pb) in Pet Food by AAS

Significance of the Topic

Monitoring heavy metals such as cadmium (Cd) and lead (Pb) in pet food is critical to ensure animal health and safety. Historic contamination incidents have led to regulatory standards that mandate strict limits. Reliable analytical methods enable manufacturers and regulatory bodies to verify compliance, prevent toxicity events, and maintain consumer confidence.

Objectives and Overview

This study demonstrates the quantification of Cd and Pb in dry pet food using both electrothermal and flame atomic absorption spectrometry (AAS) with the Shimadzu AA-7000 instrument. It compares microwave‐assisted digestion with conventional dry ashing and solvent extraction, evaluates method performance against national regulatory criteria, and assesses sensitivity, accuracy, and throughput.

Methodology and Instrumentation

Sample Preparation:

• Dry pet food was finely ground.
• For electrothermal AAS: 0.5 g sample underwent microwave digestion (ETHOS One) with nitric acid, then diluted to 50 mL.
• For flame AAS: 10 g sample was ashed at 500 °C, treated with HCl, heated, and diluted; solvent extraction using phosphoric acid, KI, and MIBK isolated analytes.

Instrument Parameters:

• Electrothermal AAS (AA-7000): wavelengths 228.8 nm (Cd), 283.3 nm (Pb); slit 0.7 nm; BGC-D2 background correction; platform graphite tubes; matrix modifier palladium nitrate (100 ppm).
• Flame AAS: air–acetylene flame; acetylene flow 0.8 L/min; calibration via extracted standards.

Main Results and Discussion

Calibration curves exhibited excellent linearity. Spike‐recovery tests (0.5 ppm Cd, 1 ppm Pb) confirmed accuracy. Measured concentrations in dog food:

• Electrothermal AAS: Cd 0.19 ppm (94 % recovery), Pb 0.26 ppm (106 % recovery).
• Flame AAS: Cd 0.20 ppm, Pb <0.3 ppm.

Both approaches met regulatory thresholds (Cd ≤1 ppm, Pb ≤3 ppm). Limits of quantitation were notably low: 0.003 ppm (Cd) and 0.07 ppm (Pb) for electrothermal, 0.01 ppm and 0.3 ppm for flame.

Benefits and Practical Applications

• Microwave digestion significantly reduces prep time compared to dry ashing and solvent extraction.
• Electrothermal AAS achieves superior sensitivity, ideal for trace-level compliance testing.
• The AA-7000 supports both flame and electrothermal modes, with optional automated switching, enhancing laboratory flexibility.

Future Trends and Opportunities

Advancements may include fully automated sample introduction systems, coupling AAS with separation techniques for multi-element screening, and development of portable AAS units for on-site pet food monitoring. Integration with laboratory information management systems (LIMS) and high-throughput sample handling will further streamline routine quality control.

Conclusion

The combined use of microwave digestion and electrothermal AAS on the AA-7000 offers a rapid, sensitive, and reliable method for Cd and Pb determination in pet food. Both electrothermal and flame approaches satisfy regulatory requirements, ensuring product safety and supporting industry quality assurance programs.

Reference

• Shimadzu Application News No. A464, Spectrophotometric Analysis: Measurement of Heavy Metals (Cd, Pb) in Pet Food by AAS, First Edition Jun. 2013.
• Ministry of Agriculture, Forestry and Fisheries Ordinance No.3, Amendment Sep.1, 2011.
• Test Method for Pet Animal Feed, Food and Agricultural Materials Inspection Center, Ministry of Agriculture, Forestry and Fisheries of Japan, No.1764, Sep.1, 2009.