Accurate and robust long-term analysis of food and beverage samples using single quadrupole ICP-MS

Importance of the Topic

The reliable detection of both essential nutrient elements and toxic heavy metals in foods and beverages is critical to consumer health and regulatory compliance.
ICP-MS is recognized for its exceptional sensitivity, but diverse sample matrices can challenge measurement accuracy.
In high-throughput laboratories, matrix effects and instrument downtime must be minimized to ensure uninterrupted, high-quality results.

Objectives and Study Overview

This study evaluates the Thermo Scientific iCAP RQplus single quadrupole ICP-MS with integrated argon gas dilution (AGD) for the long-term, multi-element analysis of 25 food and beverage types and six reference materials.
Key goals included:

• Assessing method accuracy and precision across varied matrices.
• Demonstrating robustness over extended continuous operation.
• Validating compliance with international food safety regulations.

Methodology and Instrumentation

Samples were grouped by composition: carbohydrate-rich, vegetable/fruit, spices, milk/fat, and beverages.
Solid and high-moisture foods underwent closed-vessel microwave digestion with acid mixtures, while beverages were degassed and diluted in acid.
An iCAP RQplus ICP-MS equipped with AGD and kinetic energy discrimination using helium enabled inline dilution to mitigate matrix effects.
Key instrumentation details included:

• MicroMist nebulizer with quartz cyclonic spray chamber at 2.7 °C.
• iSC-65 autosampler with overlapping uptake and rinse cycles.
• Online addition of internal standards (Sc, Y, Rh, Lu, Tl) and 4 % isopropanol for carbon compensation.
• Calibration across 26 elements from μg·L⁻¹ to 600 mg·L⁻¹.

Main Results and Discussion

Sensitivity and detection limits spanned from 0.002 μg·L⁻¹ (Be) to 0.002 mg·L⁻¹ (Na), with linearity (R² > 0.999).
Method limits of quantification met or exceeded regulatory thresholds for all target analytes.
Accuracy tests with certified reference materials showed recoveries mostly within 90–105 %.
Continuous calibration verification every ten samples and 161 QC checks across nine days confirmed calibration stability.
Internal standard recoveries remained between 85–110 % over more than nine hours of continuous analysis, demonstrating minimal drift.
Up to 270 samples per day (total 1 878) were processed over two weeks without intermediate maintenance on the plasma interface or sample introduction system.

Benefits and Practical Applications of the Method

The inline AGD approach simplifies matrix reduction, delivering:

• High throughput with consistent results across diverse food and beverage matrices.
• Extended periods between maintenance by reducing sample load in the plasma.
• Single-method capability for both digested and undigested samples.
• Compliance with global limits for both nutritional and toxic elements.

Future Trends and Potential Applications

• Integration with speciation techniques (IC-ICP MS) for distinguishing organic and inorganic forms of elements like arsenic.
• Further automation of sample preparation and online dilution control.
• Real-time data monitoring and cloud-based performance tracking via instrument software.
• Expansion to emerging contaminants and isotopic analysis in food authentication.

Conclusion

The iCAP RQplus ICP-MS with argon gas dilution provides a robust, accurate, and high-throughput solution for multi-element food and beverage testing.
Minimal maintenance, long-term stability, and broad dynamic range support regulatory compliance and laboratory efficiency.

Reference

• Commission Regulation (EC) No 1881/2006 setting maximum levels for certain contaminants in foodstuffs.
• GB-2762-2017 National Food Safety Standard for Maximum Levels of Contaminants in Foods, China.
• AOAC Official Method 2015.01: Heavy Metals in Food by ICP-MS.