Sensitive and Rapid Analysis of Inorganic Arsenic in Food and Animal Feed Samples Using LC-ICP-MS

Sensitive and Rapid Analysis of Inorganic Arsenic in Food and Animal Feed by LC-ICP-MS — Study Summary

Importance of the topic

Inorganic arsenic (iAs) is substantially more toxic than organic arsenic species and is regulated in many foodstuffs and feeds worldwide. Reliable, sensitive, and rapid analytical methods are essential for food safety, regulatory compliance, and risk assessment, especially for vulnerable populations such as infants. The study demonstrates a validated LC-ICP-MS workflow that achieves chromatographic separation of iAs from organic arsenic and chloride-derived interferences and attains detection limits suitable for strict regulatory limits, including recent baby food regulations.

Objectives and overview of the study

• Implement and validate an LC-ICP-MS method for quantifying inorganic arsenic in diverse food and animal feed matrices following EN 16802:2016 and EN 17374:2020 principles.
• Demonstrate chromatographic separation of iAs from organic arsenic species and chloride, and verify oxidation of As(III) to As(V) by sample pretreatment.
• Evaluate method performance across 14 matrices, including certified reference materials (CRMs), seafood, cereals, juices, and animal feed, and report limits of detection (LODs), recovery, and quantitative results.

Methodology and sample preparation

• Extraction: Samples extracted with 0.1 M HNO3 and 3% v/v H2O2, heated at 90 °C for 1 hour in a water bath to effect extraction and oxidative conversion of As(III) to As(V).
• Chromatography: Anion-exchange separation on HAMILTON PRP-X100 (10.0 µm, 250 mm × 4.1 mm) using eluent composed of 100 mM ammonium carbonate with 3% v/v methanol and 400 mg/L sodium sulfate adjusted to pH ~9.3. Typical run time achieved separation within 6.5 minutes.
• Interference control: Helium collision mode in the ICP-MS suppressed 40Ar35Cl at m/z 75; chromatographic conditions resolved chloride and iAs peaks to minimize matrix overlap.
• Calibration and oxidation check: iAs calibration performed using As(V) standards. A 5 µg/L As(III) standard subjected to the pretreatment yielded a measured concentration consistent with As(V) calibration (measured 4.83 µg/L), confirming oxidation to As(V).

Used instrumentation

• ICP-MS: Shimadzu ICPMS-2040/2050.
• LC: Shimadzu Nexera XS inert HPLC system controlled with LabSolutions ICPMS TRM software.
• Column: HAMILTON PRP-X100, 10.0 µm, 250 × 4.1 mm.
• Special features: Mini torch for ICP-MS reducing argon consumption to ~11 L/min, lowering operational cost for extended LC-ICP-MS runs.

Main results and discussion

• Separation and interference removal: Inorganic arsenic was effectively separated from organic arsenic species (e.g., AsB, DMA, MMA) and chloride under the selected chromatographic conditions. Helium collision mode removed 40Ar35Cl interference at m/z 75, demonstrated by comparison chromatograms and spiked sample tests.
• Oxidation validation: Pretreatment oxidized As(III) to As(V) as shown by the behavior of a 5 µg/L As(III) standard, enabling quantification using As(V)-based calibration.
• Analytical sensitivity: LODs achieved in sample matrices were low enough to meet stringent regulatory requirements (including baby food limits). Representative LODs in solid samples were in the 0.0004–0.04 mg/kg range depending on matrix; LODs in analytical solution were in the sub-µg/L range.
• Accuracy and precision: CRM analyses for brown rice (NMIJ 7532-a, 7533-a) and hijiki (NMIJ 7405-b) produced measured iAs values within certified ranges. Spike recovery across food and feed matrices ranged 96–113%, indicating robust accuracy and minimal matrix bias.
• Quantitative survey: Of the 14 matrices analyzed, most samples had little or no detectable iAs. Notable quantified values included rice cereal (0.0864 mg/kg) and animal feed (0.013 mg/kg). Seafood samples (sea bream 0.002 mg/kg; tuna and squid often below detection) contained high levels of organic arsenic (AsB) but did not interfere with iAs quantitation after separation and interference correction.

Validation and quality assurance

• CRMs: Measured values agreed with certified ranges (e.g., brown rice CRMs within stated uncertainty), supporting method trueness.
• Spike recovery: 96–113% recovery across matrices confirmed method accuracy and matrix tolerance.
• Regulatory suitability: Detection limits and method specificity satisfied current regulatory limits cited (EU regulations and baby food safety considerations).

Benefits and practical applications of the method

• Rapid throughput: Chromatographic separation and run time (<6.5 min) enable relatively high sample throughput for routine monitoring.
• Robust interference control: Combination of anion-exchange separation and He collision mode reduces chloride- and matrix-derived spectral interferences, improving reliability in complex foods and feeds.
• Operational efficiency: Use of a mini torch reduces argon consumption, lowering running costs for routine LC-ICP-MS monitoring labs.
• Regulatory monitoring: Method sensitivity and validation make it suitable for compliance testing against stringent inorganic arsenic limits, including those for baby foods and feeds.

Future trends and potential applications

• Broader matrix application: The validated workflow can be extended to additional complex matrices (processed foods, dietary supplements) with tailored extraction/cleanup to maintain accuracy.
• Automation and high throughput: Integration with autosamplers, faster chromatographic phases, or multiplexed ICP-MS systems could increase laboratory throughput while maintaining sensitivity.
• Speciation coupling: Complementary hyphenated techniques (e.g., ICP-MS with high-resolution MS or tandem MS) may improve identification of minor arsenic species and support source attribution studies.
• Method harmonization: Continued alignment with evolving international regulations and standardization bodies will support wider adoption in regulatory and commercial testing laboratories.

Conclusion

The study demonstrates a validated, sensitive, and rapid LC-ICP-MS method for inorganic arsenic determination across diverse food and feed matrices. Effective sample pretreatment converts As(III) to As(V), chromatography separates iAs from organic arsenic and chloride, and helium collision mode removes chloride-related spectral interference. Accuracy was confirmed by CRM analysis and spike recoveries, and detection limits met strict regulatory requirements, supporting routine use for food safety monitoring and regulatory compliance.

References

1. EN 16802:2016 Determination of inorganic arsenic in foodstuffs of marine and plant origin by anion-exchange HPLC-ICP-MS.
2. EN 17374:2020 Determination of inorganic arsenic in animal feed by anion-exchange HPLC-ICP-MS.
3. Commission Regulation (EU) 2023/915 on maximum levels for certain contaminants in food.
4. Commission Regulation (EU) 2025/1891 amending Regulation (EU) 2023/915 regarding inorganic arsenic in fish and seafood.
5. The Baby Food Safety Act of 2021 (contextual regulatory driver referenced in the study).
6. Directive 2002/32/EC on undesirable substances in animal feed.