Determination of arsenic in food and beverages with pure oxygen reactive gas using the Thermo Scientific iCAP RQ ICP-MS

Significance of the Topic

Arsenic contamination in food and beverages poses serious health risks due to its toxicity and prevalence in the environment. Reliable quantification of total arsenic content, particularly inorganic species, is critical for food safety monitoring and regulatory compliance. The method described leverages modern ICP-MS technology to address analytical challenges and deliver accurate results.

Objectives and Overview

This study aims to demonstrate interference-free determination of arsenic in rice and mixed fruit juice using pure oxygen as a reaction gas on a Thermo Scientific iCAP RQ ICP-MS. The focus is on converting arsenic ions into AsO+ product ions to overcome polyatomic interferences from chloride and argon species.

Methodology

Sample preparation:

• Rice: 0.2 g finely ground sample digested with HNO₃, HCl and H₂O₂ via microwave digestion.
• Fruit juice: 0.5 g sample treated with the same acid mixture in Anton Paar Multiwave PRO.
• Post-digestion solutions diluted to 20 mL with ultrapure water.
• A preparation blank processed identically without sample.

Used Instrumentation

• Thermo Scientific iCAP RQ ICP-MS with Qtegra ISDS Software.
• Collision/reaction cell operated in He KED mode and O₂ CCT mode.
• PFA-ST nebulizer, quartz cyclonic spray chamber at 2.7 °C, quartz injector.
• Anton Paar Multiwave PRO microwave digestion system.

Main Results and Discussion

• Oxygen reaction gas produced mass-shifted 75As16O+ at m/z 91, eliminating 40Ar35Cl+ and 40Ca35Cl+ interferences.
• O₂ CCT mode showed higher sensitivity (7612 vs 2953 cps·µg⁻¹·L), lower BEC (3 vs 26 ng·L⁻¹) and IDL (2 vs 14 ng·L⁻¹) compared to He KED.
• Detected arsenic levels in both matrices were below 1 µg·L⁻¹, within regulatory limits.
• Spike recovery (0.25 µg·L⁻¹ rice, 0.5 µg·L⁻¹ juice) averaged 98% and 97% with RSD < 2%.
• Data confirm that microwave digestion fully decomposes organic matrix and the reactive gas approach ensures accurate low-level arsenic analysis.

Benefits and Practical Applications

• Robust interference removal enhances detection limits and accuracy for trace arsenic determination.
• Straightforward method setup via autotune routines improves laboratory efficiency.
• Suitable for routine food safety monitoring and compliance with international standards.

Future Trends and Potential Applications

• Extension to arsenic speciation for differentiating organic and inorganic forms.
• Automation and high-throughput workflows for large-scale food screening.
• Adoption of reactive gas strategies for other challenging elements and sample matrices.

Conclusion

Pure oxygen reaction gas on the iCAP RQ ICP-MS enables precise, interference-free quantification of total arsenic in rice and fruit juice by converting analyte ions to AsO+. The method achieves excellent accuracy, low detection limits and meets regulatory requirements, supporting its application in food safety analysis.