Abstract
Two samples of mussels (Mytilus edulis) were collected from the southwest of Ireland. One sample contained domoic acid, the other sample contained okadaic acid, dinophysistoxin-2 and azaspiracid-1, -2 and -3. Wet and freeze-dried reference materials were prepared from each of the two samples to test for differences in homogeneity, stability and extractability of the analytes in either condition. Wet materials were homogenised, aliquoted and hermetically sealed under argon and subsequently frozen at −80 °C. Dry materials were similarly homogenised but frozen in flat cakes prior to freeze-drying. After grinding, sieving and further homogenisation, the resulting powder was aliquoted and hermetically sealed. Domoic acid materials were characterised using HPLC–UV, while LC–MS was used for the determination of lipophilic toxins. The extractabilities of all phycotoxins studied were comparable for wet and freeze-dried materials once a sonication step had been carried out for reconstitution of the freeze-dried materials prior to extraction. Homogeneity was assessed through replicate analysis of the phycotoxins (n = 10), and was found to be similar for wet and freeze-dried materials, for both hydrophilic and lipophilic toxins. Water contents were determined for both wet and freeze-dried materials, and particle size was determined for the freeze-dried materials. Stability was evaluated isochronously over eight months at four temperatures (−20, +4, +20 and +40 °C). The freeze-dried material containing domoic acid was stable over the whole duration at all temperatures, while in the wet material domoic acid degraded to some extent at all temperatures except −20 °C. In freeze-dried and wet materials containing lipophilic toxins, okadaic acid, dinophysistoxin-2, azaspiracid-1 and azaspiracid-2 were stable over the whole duration at all conditions, while concentrations of azaspiracid-3 changed significantly in both materials at some storage temperatures.
Aliquots of freeze-dried and wet mussel tissue reference materials containing the various shellfish toxins examined in the study
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Acknowledgements
We would like to acknowledge the technical assistance of the staff in both the Reference Material Processing group at the IRMM and the Biotoxin Chemistry team at the Marine Institute. The authors would also like to thank Franz Ulberth (IRMM) for his valuable input in the planning and organisation of this study. The Marine Institute and the National Development Plan (NDP) provided funds to the ASTOX project (ST/02/02, 2003–2006). BIOTOX is an EU-funded project under FP6 (project no. 514074).
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McCarron, P., Emteborg, H. & Hess, P. Freeze-drying for the stabilisation of shellfish toxins in mussel tissue (Mytilus edulis) reference materials. Anal Bioanal Chem 387, 2475–2486 (2007). https://doi.org/10.1007/s00216-006-1104-z
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DOI: https://doi.org/10.1007/s00216-006-1104-z