Elemental Analysis with Mercury Speciation in Honey Using LC-ICP-MS

Importance of the Topic

Honey is valued for its nutritional content and trace minerals but can accumulate harmful elements like lead, cadmium and mercury from environmental sources. Monitoring essential and toxic metals and mercury species in honey is crucial for consumer safety and regulatory compliance.

Study Objectives and Overview

This study aims to quantify essential (Cu, Sn, Zn) and toxic elements (As, Cd, Pb, Hg) and to perform speciation of inorganic mercury and methylmercury in honey. A Shimadzu LC-ICP-MS system was employed to achieve rapid and sensitive analysis in accordance with FSSAI and WHO guidelines.

Methodology and Instrumentation

Sample Preparation:

• Microwave digestion of honey with nitric acid and hydrogen peroxide.
• Triplicate digestions diluted to 50 mL for total element analysis.
• Sample dilution in 0.1% L-cysteine for mercury speciation.

ICP-MS Conditions:

• Shimadzu ICPMS-2030 with AS-10 autosampler.
• RF power 1.2 kW, plasma gas 8 L/min, helium collision gas.
• Detection limits in low ng/L range.

HPLC Conditions for Speciation:

• Shimadzu LC-20Ai inert system with Synergi Hydro RP column.
• Mobile phase: 0.1% L-cysteine pH 2.5, flow 1.2 mL/min.
• Run time 5 minutes per sample.

Main Results and Discussion

Multi-element calibration curves showed linearity with correlation coefficients >0.999. Instrument detection limits corresponded to LOQs below FSSAI maximum limits (As: 0.11 µg/g, Cd: 0.15 µg/g, Cu: 3 µg/g, Hg: 0.1 µg/g, Pb: 0.25 µg/g, Sn: 2.5 µg/g, Zn: 5 µg/g). Recoveries at 10% and 20% of regulatory limits ranged between 90–120% with RSD <3%. All element concentrations in the honey sample were below LOQ.

Mercury speciation separated inorganic and methylmercury in under five minutes. LOQ for mercury species was 4 µg/kg in honey. Recoveries at 0.2 and 0.5 µg/L spikes were 94–110% with RSD <5%.

Benefits and Practical Applications

The LC-ICP-MS method provides:

• Simultaneous quantification of essential and toxic elements.
• Fast and robust mercury speciation.
• High sensitivity meeting food safety regulations.
• Centralized data handling via TRM software.

Future Trends and Opportunities

Advancements may include coupling with tandem MS for improved selectivity, miniaturized or portable ICP-MS units for field testing, automation of sample preparation, application to diverse food matrices, and integration of advanced data analytics for rapid quality assessment.

Conclusion

The combined LC-ICP-MS approach using Shimadzu instrumentation delivers fast, sensitive and reliable multi-element determination and mercury speciation in honey, ensuring compliance with regulatory standards and supporting food safety monitoring.

Reference

• World Health Organization. Mercury and Health, WHO Fact Sheet, 2017.
• Food Safety and Standards Authority of India. Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2011.
• Food Safety and Standards Authority of India. Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2006.
• Briscoe M. Determination of Heavy Metals in Food by Inductively Coupled Plasma-Mass Spectrometry: First Action 2015.01, J. AOAC Int., 2015, 98(4), 1113–1120.