Speciation of Methyl Mercury and Mercury in Honey using High Performance Liquid Chromatography hyphenated with Inductively Coupled Plasma Mass Spectrometry

Importance of the Topic

Mercury contamination of food products poses serious health risks due to its neurotoxicity and bioaccumulation. Methyl mercury, a more toxic organic form produced by microbial methylation, can accumulate in honey through environmental pollution. Reliable speciation of total mercury and methyl mercury in honey is essential for food safety compliance and public health protection.

Objectives and Overview of the Study

This study aimed to develop and validate a rapid, sensitive method for simultaneous determination of methyl mercury and inorganic mercury in honey. The method employs high-performance liquid chromatography (HPLC) to separate species, hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) for ultra-trace detection, and meets the Food Safety and Standards Authority of India (FSSAI) limits.

Methodology

Sample Preparation:

• Accurately weigh 0.5 g honey into a 10 mL flask.
• Dilute to mark with mobile phase (0.1 % L-cysteine, pH 2.5).
• Vortex and heat at 60 °C for 2 h.
• Cool, filter (0.45 µm nylon), and transfer to HPLC vials.

Used Instrumentation

Shimadzu Inert LC system coupled to an ICPMS-2030 was employed. Chromatographic parameters (mobile phase composition, flow rate, column temperature) and ICP-MS tune conditions were optimized for baseline separation and low-ppb detection.

Main Results and Discussion

Calibration and Linearity:

• Calibration range: 0.1–10 ppb for both species.
• Correlation coefficient ≥ 0.999, indicating excellent linearity.

Chromatographic Performance:

• Complete separation of methyl mercury and inorganic mercury achieved in under 5 minutes.

Accuracy and Precision:

• ICV/CCV accuracy between 90–100 %, demonstrating system robustness over extended runs.
• Spike recoveries at 0.2, 0.5, and 1.0 ppb yielded 80–120 % recovery and RSD < 5 %, confirming method reliability.

Sample Results:
Methyl mercury and total mercury levels in tested honey samples were below 4 ppb, well within regulatory limits.

Benefits and Practical Applications

The proposed HPLC-ICP-MS method offers:

• Rapid analysis with minimal sample preparation.
• High sensitivity for low-ppb detection.
• Robust reproducibility for routine quality control.

It is suitable for compliance testing in food safety laboratories and regulatory agencies.

Future Trends and Opportunities

Advances may include automated on-line sample preparation to further increase throughput, miniaturized chromatographic systems for field deployment, and coupling with high-resolution ICP-MS to enhance selectivity. Expanding the method to other food matrices and environmental samples can broaden its application scope.

Conclusion

A validated HPLC-ICP-MS method was successfully developed for rapid speciation of methyl mercury and inorganic mercury in honey. It meets FSSAI requirements, delivers excellent accuracy and precision at low concentration levels, and can be adopted for routine monitoring of mercury contamination in food products.