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

Significance of the Topic

Arsenic speciation in nutritional products is critical for food safety and human health because toxicity depends on chemical form. Inorganic arsenic species As(III) and As(V) pose greater carcinogenic risks than organic forms such as DMA and MMA. Accurate quantification of individual species informs risk assessment and ensures compliance with regulatory limits.

Objectives and Study Overview

This feasibility study aimed to evaluate the performance of an Agilent 1260 high performance liquid chromatography system coupled to an Agilent 7900 ICP-MS for simultaneous determination of four arsenic species in raw ingredients and milk based nutritional products. Collaborative analysis was performed at Abbott Nutrition and University of California Davis laboratories to assess method robustness and inter laboratory comparability.

Methodology

Sample Preparation

• Microwave assisted extraction at 90C for 60 minutes followed by cooling
• Extraction blanks used for LOD and LOQ calculations

Chromatographic Conditions

• Column PRP X100 10 µm 250 x 4.6 mm at 20C
• Mobile phases of 0.5 mM and 15 mM ammonium citrate at pH 4.5 and pH 8 respectively
• Gradient program over 12 minutes with flow rate 0.5 mL per minute, injection volume 100 µL

Sensitivity and Quantitation

• Instrument LOD defined as 3 times standard deviation of baseline noise
• LOQ determined as 3.3 times LOD or blank mean plus 10 sigma and adjusted for dilution
• Achieved LOQ values around 2.5 ng per g for inorganic species and 5 ng per g for powders

Used Instrumentation

• Agilent 1260 HPLC system with PRP X100 column
• Agilent 7900 ICP-MS operated in kinetic energy discrimination mode with helium collision gas
• Microwave digestion system at 1600 W power

Main Results and Discussion

• NIST SRM recoveries ranged from 87 to 107 percent for individual arsenic species demonstrating accuracy across two laboratories
• Inorganic arsenic (sum of As(III) and As(V)) was the predominant form in raw ingredients like rice flour and whey concentrate and in nutritional powders
• Dimethylarsinic acid and monomethylarsonic acid were below LOQ in most samples
• Inter laboratory comparison between Abbott Nutrition and UC Davis showed recoveries within 5 percent and good precision

Benefits and Practical Applications

• High sensitivity and low quantitation limits meet regulatory requirements for arsenic in foods
• Robust method suitable for diverse sample types such as powders, concentrates and liquids
• Reproducible results across independent laboratories support method reliability for quality control and research

Future Trends and Application Opportunities

• Extension of validated speciation methods to include organic arsenic variants like arsenobetaine and arsenocholine
• Integration with high resolution mass spectrometry for enhanced identification of unknown arsenic compounds
• Development of rapid and miniaturized sample preparation workflows for high throughput screening
• Standardization of hyphenated speciation protocols across regulatory and industrial laboratories

Conclusion

The combined Agilent 1260 HPLC and 7900 ICP-MS platform provides accurate, precise and sensitive arsenic speciation in nutritional ingredients and products. The method demonstrates strong inter laboratory agreement and meets analytical performance criteria. Future work will focus on full method validation and expansion to additional arsenic species.