Feasibility Study for the Determination of Arsenic Species in Nutritional Products and Raw Ingredients by HPLC-ICP-MS

Importance of the Topic

The speciation of arsenic in food matrices is critical due to wide variation in toxicity among its chemical forms. Inorganic arsenic species such as arsenite and arsenate exhibit higher carcinogenic potential compared to organic forms like DMA and MMA. Assessing individual arsenic species in nutritional products and raw ingredients enables accurate risk assessment and compliance with regulatory limits.

Objectives and Study Overview

This study evaluates the feasibility of coupling an Agilent 1260 high-performance liquid chromatograph (HPLC) with an Agilent 7900 inductively coupled plasma-mass spectrometer (ICP-MS) for quantifying four arsenic species in nutritional products and raw ingredients. Experiments were performed at Abbott Nutrition and UC Davis laboratories to compare analytical performance across sites.

Methodology and Instrumentation

Sample preparation involved microwave-assisted extraction (1 600 W power, ramp to 90 °C in 10 min, 60 min hold, 20 min cool down). Chromatographic separation was achieved on a PRP-X100 column (250×4.6 mm, 10 µm) at 20 °C using a gradient of 0.5 mM and 15 mM ammonium citrate buffers (pH 4.5 and 8), a flow rate of 0.5 mL/min, and a 100 µL injection volume over a 20 min run time.

ICP-MS detection employed an Agilent 7900 instrument in kinetic energy discrimination mode with helium cell gas, RF power at 1550 W, and nebulizer and auxiliary gas flows of 1.08 L/min and 0.90 L/min. UC Davis also evaluated a triple-quadrupole ICP-MS in single-quadrupole mode. Calibration used multi-level standards for As(III), As(V), DMA, and MMA.

Key Results and Discussion

The method achieved instrument limits of detection (LOD) and quantification (LOQ) suitable for regulatory thresholds, with LOQ values of approximately 2.5 ng/g for arsenic species in liquid samples and 5 ng/g in powders. Spike recoveries in certified reference materials ranged from 94 % to 105 %. Analyses of NIST SRMs and real-world samples confirmed accuracy (recoveries within 87 %–107 %) and precision (RSD ≤ 10 %). Inorganic arsenic dominated all tested matrices, while DMA was detected in rice syrup at ~14 µg/kg; MMA and other organoarsenicals were below quantifiable levels in most samples.

Benefits and Practical Applications

• The combined HPLC-ICP-MS system offers high sensitivity and selectivity for arsenic speciation in complex matrices.
• Validated performance across two laboratories demonstrates robust reproducibility and method transferability.
• The approach meets current regulatory requirements for monitoring inorganic arsenic in food and nutritional products.

Future Trends and Opportunities

Advancements may include full validation for all relevant arsenic species, extension to additional food matrices, and incorporation of triple-quadrupole ICP-MS for enhanced interference removal. Automated sample preparation and miniaturized flow systems could further improve throughput and reduce reagent consumption.

Conclusion

This feasibility study confirms that an Agilent 1260 HPLC coupled to an Agilent 7900 ICP-MS provides accurate, precise, and sensitive arsenic speciation in nutritional products and raw ingredients. The method is suitable for routine compliance testing and can be further refined to cover a broader range of arsenic species and sample types.