Fast Determination of Inorganic Arsenic (iAs) in Food and Animal Feed by HPLC-ICP-MS

Significance of the Topic

A rapid and reliable determination of inorganic arsenic (iAs) in food and animal feed is essential to protect public health. The two more toxic inorganic forms, arsenite (As(III)) and arsenate (As(V)), require strict monitoring under EU Regulation 1881/2006 for rice products and Directive 2002/32/EC for feed. Growing regulatory interest in iAs levels in water, dairy, and other widely consumed foods underscores the need for efficient analytical methods.

Objectives and Study Overview

This study aimed to optimize and validate a fast HPLC-ICP-MS method for routine control of iAs in diverse matrices. The approach was aligned with European regulations and two CEN standards: EN16802:2016 (food) and prEN17374:2019 (animal feed). Key goals were to achieve baseline separation of iAs within two minutes and demonstrate fitness for official control.

Methodology and Instrumentation

Sample Preparation

• Solid samples: ~0.2 g mixed with 10 mL of 0.1 M HNO₃/3 % H₂O₂, heated at 90 °C for 60 min, centrifuged, then filtered (0.45 µm).
• Liquid samples: 5 mL sample combined with 5 mL of 0.2 M HNO₃/6 % H₂O₂, processed as for solids.
• High-As samples (e.g., Hijiki): additional 20× dilution prior to analysis.

Used Instrumentation

• HPLC: Agilent 1260 binary pump, PRP-X100 column (5 µm, 50×2.1 mm) with guard.
• Mobile phase: 40 mM ammonium carbonate/3 % methanol, pH 9; isocratic at 0.65 mL/min; 5 µL injection; 5 min total runtime.
• ICP-MS: Agilent 8900 Triple-Quadrupole in single-quad mode using He collision gas (3.5 mL/min); monitored m/z 75 for As.

Main Results and Discussion

Chromatographic Performance

• Complete baseline separation of As(V) from dimethylarsinic acid (DMA), monomethylarsonic acid (MA), arsenobetaine, and Cl interference in under two minutes.
• Retention time stability: RSD ≤ 1.7 % across sequences.

Sensitivity and Calibration

• Linear response for iAs (0.05–50 µg/L), R² > 0.999.
• LODs/LOQs: 1.99/6.64 µg/kg in solids, 0.08/0.27 µg/L in liquids; exceeding EU requirements.

Accuracy and Precision

• Spike recoveries: 90–111 % for most matrices; apple juice required standard-addition due to matrix effects.
• Precision (RSD): 0.3–9.4 % across reference materials and samples.
• Recoveries vs. certified values: 81.8–110.7 %.

Benefits and Practical Applications

This rapid HPLC-ICP-MS protocol reduces analysis time compared to traditional long-column methods, boosting laboratory throughput. It meets EU and CEN standard requirements for official control and can be implemented on single-quad or triple-quad ICP-MS platforms. Its high sensitivity allows detection of trace iAs in high-risk commodities, supporting food safety and regulatory compliance.

Future Trends and Opportunities

• Integration of ultra-high-pressure liquid chromatography (UHPLC) to further shorten run times
• Expansion to additional matrices such as dairy and processed foods
• Automation of sample preparation via robotic platforms
• Use of advanced reaction gases and MS/MS for improved interference removal
• Development of portable speciation systems for on-site screening

Conclusion

A fast, robust HPLC-ICP-MS method was established for inorganic arsenic determination in food and feed. By converting all iAs to As(V) during extraction and using a short anion-exchange column, the protocol achieves reliable, two-minute separations with excellent sensitivity, accuracy, and precision. It fully complies with EU regulations and CEN standards, offering a practical solution for routine monitoring of this critical contaminant.

References

• EFSA, Scientific Opinion on Arsenic in Food, EFSA Journal 2009, 7, 1351.
• EU Commission Regulation (EC) No 1881/2006.
• EU Directive 2002/32/EC on undesirable substances in animal feed.
• B.P. Jackson, J. Anal. At. Spectrom. 2015, 30, 1405.
• P.J. Gray et al., J. Anal. At. Spectrom. 2017, 32, 1031.
• CEN EN16802:2016; prEN17374:2019.