Determination of Arsenic Species in Apple Juice by LC-ICP-MS Analysis

Importance of the Topic

Arsenic contamination poses significant health risks due to its varying toxicity across different chemical forms. Assessing inorganic and organic arsenic species in foods such as apple juice is critical for consumer safety and regulatory compliance. Advanced analytical techniques that differentiate and quantify these species with high sensitivity are essential in food quality monitoring and risk assessment.

Objectives and Study Overview

This study aims to demonstrate the application of liquid chromatography coupled with inductively coupled plasma mass spectrometry (LC-ICP-MS) for speciation analysis of arsenic in apple juice. Key goals include optimizing sample preparation, evaluating instrument performance, determining detection limits, and verifying recovery rates for common arsenic species.

Methodology

• Sample Preparation: 2 mL of commercial apple juice diluted with 0.1 mL of 100 mmol/L phosphoric acid and made up to 10 mL with 0.15 mol/L nitric acid.
• Chromatographic Separation: Sigma-Aldrich Discovery HS F5 column (250×4.6 mm, 5 µm) with Shim-pack GIST guard column. Mobile phase: 0.1% formic acid with 1% methanol and 0.025% tetramethylammonium hydroxide at 0.75 mL/min, column oven at 40 °C, 10 µL injection, 6 min run time.
• ICP-MS Detection: Shimadzu ICPMS-2030 with 1.2 kW RF power, helium collision gas, plasma gas flow 9 L/min, auxiliary gas 1.1 L/min, carrier gas 0.7 L/min, Nebulizer 07, cyclone chamber, mini-torch.
• Calibration and Validation: Calibration curves for As III, As V, MMA, DMA from 0.2 to 1 µg/L; lower limit of detection calculated as 3σ of ten replicates at 0.2 µg/L; spike-and-recovery tests at 1 µg/L.

Used Instrumentation

• Shimadzu Nexera Series HPLC system
• Shimadzu ICPMS-2030 inductively coupled plasma mass spectrometer
• LabSolutions ICPMS TRM software for instrument control and data analysis

Main Results and Discussion

• Detection Limits: LODs below 0.05 µg/L for all species (As V: 0.04, As III: 0.03, MMA: 0.04, DMA: 0.03 µg/L), demonstrating high sensitivity.
• Quantitative Results: Native apple juice contained 0.09 µg/L As V, 0.27 µg/L As III, 0.15 µg/L MMA, and <0.03 µg/L DMA.
• Recovery Rates: Spike recoveries between 97% and 101%, confirming method accuracy.
• Regulatory Compliance: Measured levels of inorganic arsenic were below the FDA action level of 10 µg/kg, indicating product safety.

Practical Benefits and Applications

• Provides a robust workflow for routine speciation of arsenic in food matrices.
• Helps laboratories comply with regulatory standards and ensure consumer safety.
• Method package reduces setup time by pre-configuring analytical conditions.

Future Trends and Potential Applications

Advances in hyphenated techniques and high-resolution mass spectrometry may further lower detection limits and enhance speciation capabilities. Emerging fields such as metabolomics and environmental monitoring could benefit from improved arsenic speciation protocols. Integration with automation and data analytics platforms will streamline high-throughput screening and real-time quality control.

Conclusion

The LC-ICP-MS approach effectively separates and quantifies toxicologically relevant arsenic species in apple juice with high sensitivity and accuracy. The method meets regulatory requirements and offers a practical tool for ensuring food safety.

References

• Food and Drug Administration. FDA Issues Final Guidance to Industry on Action Level for Inorganic Arsenic in Apple Juice. June 8, 2023.
• Food and Drug Administration. Guidance for Industry: Action Level for Inorganic Arsenic in Apple Juice. June 8, 2023.