Fast, Accurate Analysis of Metal Contaminants in Edible Coconut Products using ICP-MS

Importance of the Topic

Trace metal contamination in food products poses serious health risks when heavy metals such as lead, arsenic, cadmium and mercury exceed regulatory limits. Coconut-derived foods—oil, milk and powder—are consumed globally and require reliable monitoring to ensure safety and compliance with standards such as India’s FSSAI regulations. High-throughput, sensitive multi‐element analysis is essential for routine screening and quality control in food laboratories.

Objectives and Study Overview

This study aimed to develop and validate a fast, accurate ICP‐MS method compliant with FSSAI limits for elemental contaminants in coconut products. The key objectives were to:

• Digest diverse coconut matrices (oil, milk, powder) by microwave‐assisted acid digestion.
• Quantify Pb, As, Cd, Hg, Sn, Cu and Ni using an Agilent 7850 ICP‐MS in helium collision (He KED) mode.
• Demonstrate method linearity, detection limits, precision, accuracy and regulatory compliance.

Methodology and Instrumentation

Sample preparation involved weighing 0.5 g of each product in triplicate and digesting with HNO₃/HCl in an Anton‐Paar Go microwave system (three‐stage program up to 180 °C). Digests were diluted to 25 mL (50× dilution) and analyzed alongside method blanks and spiked samples.
Calibration standards (0.05–1000 ppb, 0.05–10 ppb for Hg) were prepared in 2% HNO₃/1% HCl to stabilize volatile elements. An online internal standard mix (Li, Sc, Ge, Rh, Tb, Lu, Bi, Ir) was introduced at low flow to correct drift. All elements were measured in He KED mode to control polyatomic interferences.

Used Instrumentation

• Agilent 7850 ICP‐MS with ORS4 collision/reaction cell (He KED) and UHMI aerosol dilution.
• Agilent SPS 4 autosampler for automated sample introduction.
• MicroMist concentric nebulizer, quartz spray chamber, quartz torch with 2.5 mm injector.
• Nickel‐plated sampling and skimmer cones.
• Multi‐element calibration standards (Agilent p/n 8500-6940, 8500-6948) and internal standard mix (p/n 5188-6525).

Main Results and Discussion

Calibration linearity was excellent (R > 0.9999) for all analytes. Instrument detection limits (IDLs) and method detection limits (MDLs) were well below FSSAI maximum limits (e.g., MDLs < 1 ppb after dilution). Quantitative analysis of coconut oil, milk and powder showed contaminant levels below regulatory thresholds; copper and nickel were detected at low µg/g levels in milk and powder only.
Spike‐recovery tests at three levels (0.005–0.02 mg/kg) yielded 80–120% recoveries, meeting AOAC criteria. Within‐day repeatability and between‐day reproducibility were both below 5% RSD. Internal standard recoveries remained within ±20% over a two‐hour run, demonstrating excellent stability and matrix robustness. IntelliQuant screening enabled rapid semiquantitative profiling of up to 78 elements, revealing matrix‐specific variations such as sodium content in milk (78 ppm) versus oil (188 ppb) and powder (5 ppm).

Benefits and Practical Applications of the Method

• Simultaneous multi‐element analysis in a single run reduces reruns and saves time.
• Low detection limits ensure compliance with stringent food safety standards.
• Robust plasma operation and UHMI support high‐matrix samples without frequent maintenance.
• IntelliQuant screening adds value by identifying unexpected contaminants.

Future Trends and Opportunities

Emerging trends include integration of automated sample preparation, coupling ICP‐MS with chromatography for speciation analysis, adoption of reaction gases for interference reduction, and broader application to diverse food matrices. Advances in software algorithms and high‐throughput robotics will further speed up food safety testing.

Conclusion

The validated method using Agilent 7850 ICP‐MS in helium mode provides reliable, accurate detection of heavy metals in edible coconut products, fully compliant with FSSAI regulations. High sensitivity, strong reproducibility and ease of use make it ideal for routine food safety laboratories.

References

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