Easy and fast method development for the mercury speciation in food by HPLC-ICP-MS

Importance of the Topic

Mercury poses a serious threat to human health due to its bioaccumulation and varying toxicity among different chemical forms. Accurate speciation analysis in food matrices is essential for risk assessment and regulatory compliance, as total mercury measurements alone cannot distinguish between more and less toxic species.

Objectives and Study Overview

This study aimed to develop a rapid and robust method for the simultaneous separation and quantification of four mercury species (inorganic Hg2+, methylmercury, ethylmercury and phenylmercury) in food samples using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Certified reference materials were used to validate the accuracy and precision of the approach.

Methodology and Instrumentation

Chromatographic separation employed an Agilent 1260 HPLC system with a Zorbax C18 column (4.6×50 mm, 1.8 µm). A gradient elution from 2% to 90% methanol in 3 minutes increased resolution and throughput. Sample extracts were obtained by microwave-assisted extraction of reference tuna muscle and dogfish liver materials in acidic cysteine solution, followed by filtration and direct injection.

Instrumentation Used

• Agilent 1260 HPLC with binary pump and autosampler
• Zorbax C18 column, 4.6×50 mm, 1.8 µm
• Agilent 7700x ICP-MS with platinum cones and 1.0 mm injector torch
• Oxygen addition (20% O2 in Ar) to maintain plasma stability with high organic load
• Microwave extractor operating at 140 W for sample digestion

Main Results and Discussion

Under the optimized gradient, all four mercury species were baseline-separated in under three minutes. The 7700x RF generator maintained a stable plasma even when methanol content rapidly increased to 90% and returned to 2%. Calibration curves for each species were linear across 80 ng/L to 8 µg/L (inorganic and phenylmercury) and 62 ng/L to 6.2 µg/L (methylmercury), with background equivalent concentrations below 15 ng/L. Analysis of two certified reference materials yielded recoveries between 94% and 101% for methylmercury and inorganic mercury, with relative standard deviations under 10%.

Benefits and Practical Applications

The method offers high throughput and sensitivity at ppt levels, making it well suited for routine monitoring in food safety laboratories, quality control and regulatory testing. The rapid analysis time reduces solvent consumption and instrument downtime, while the robust plasma operation allows seamless switching between aqueous and high-organic mobile phases.

Future Trends and Potential Applications

Advances in RF generator technology and software integration are likely to further shorten analysis times and expand compatibility with a broader range of organic solvents. Future work may explore multi-element speciation, on-line sample preconcentration, and application to complex environmental and biological matrices. Automation and miniaturization could improve accessibility in field-deployable systems.

Conclusion

A fast, reliable HPLC-ICP-MS method was developed for mercury speciation in food, achieving complete separation in less than three minutes, ppt-level sensitivity, and excellent accuracy against certified standards. The approach provides a valuable tool for comprehensive mercury monitoring, combining speed, precision, and operational robustness.

References

No formal literature references were listed in the source document.