Validated Method for the Analysis of Lipophilic Marine Biotoxins in Bivalves by Liquid Chromatography—High-Resolution Mass Spectrometry

Importance of the Topic

Harmful algal blooms generate lipophilic marine biotoxins (MBTXs) that accumulate in filter-feeding bivalve mollusks and pose serious health risks to consumers. Regulatory frameworks such as EU Regulations (EC) No 853/2004 and (EU) 786/2013 set maximum limits for MBTXs to protect public health and support sustainable shellfish trade.

Objectives and Study Overview

This study presents a validated confirmatory method for quantitative analysis of major lipophilic marine biotoxins in fresh and canned bivalves. The approach integrates a QuEChERS-based sample preparation with ultra-high-performance liquid chromatography coupled to high-resolution tandem mass spectrometry (UHPLC-HRMS/MS), achieving a lower quantitation limit of 25 µg/kg and compliance with EU legislative requirements.

Methodology

• Sample Preparation: A QuEChERS protocol using 1 g of bivalve tissue, acetonitrile extraction with NaCl and MgSO4, dispersive C18 cleanup, evaporation under nitrogen at 45 °C, and reconstitution in ammonium-buffered mobile phase.
• Hydrolysis Step: Alkaline hydrolysis was applied to quantify total okadaic acid equivalents by converting esterified forms to free acid.
• Validation Parameters: Specificity assessed in blank mussel, clam, cockle, and razor clam matrices; linearity over 25–350 µg/kg with r2 ≥ 0.9998; recoveries between 79% and 114%; relative standard deviations from 1.5% to 18.7%; precision and trueness verified using certified reference materials.

Instrumentation

• UHPLC System: Thermo Scientific Accela with a C18 column (100 × 2.1 mm, 1.7 µm).
• Mass Spectrometer: Thermo Scientific Q Exactive quadrupole-Orbitrap operated in data-dependent HRMS/MS mode.
• Mobile Phases: (A) 6.7 mM ammonium hydroxide in water, (B) acetonitrile; gradient elution at 0.25 mL/min, 5 µL injection.
• Data Processing: Thermo Scientific TraceFinder software version 3.1.

Main Results and Discussion

• Mass accuracy was maintained within 5 ppm for both molecular and product ions of each analyte.
• Sensitivity: Lower limit of quantitation at 25 µg/kg for all target compounds.
• Linearity: Excellent calibration curves with residuals below 25% at the LLOQ and under 15% at higher levels.
• Validation against certified reference mussel materials demonstrated trueness ranging from 91.4% to 105.2%, confirming method reliability.

Benefits and Practical Applications

• The QuEChERS extraction simplifies sample handling and reduces solvent usage while ensuring high recovery and minimal matrix effects.
• UHPLC-HRMS/MS provides rapid, high-resolution detection and robust quantitation suitable for routine monitoring and official control of MBTXs in diverse bivalve species.
• Matrix-matched calibration using surrogate standards enhances quantification accuracy across different shellfish matrices.

Future Trends and Applications

Emerging opportunities include expanding the scope to non-target screening of novel marine toxins, integrating automated sample preparation for high-throughput laboratories, and leveraging advanced data-analysis workflows with machine learning to improve detection and identification of toxin analogs.

Conclusion

The validated QuEChERS-UHPLC-HRMS/MS workflow delivers a cost-effective, sensitive, and robust solution for the quantification of lipophilic marine biotoxins in bivalves, fully aligned with EU regulatory standards and adaptable to routine analytical and research environments.

References

1. Rúbies A, et al. New method for the analysis of lipophilic marine biotoxins in fresh and canned bivalves by liquid chromatography coupled to high-resolution mass spectrometry. Journal of Chromatography A. 2015;1386:62–73.
2. Regulation (EC) No 853/2004. Official Journal of the European Union. 2004;L139:55.
3. Commission Regulation (EU) No 786/2013. Official Journal of the European Union. 2013;L220:14.