Evaluation of Accelerated Solvent Extraction and Solid-Phase Micro Extraction for the Analysis of Brevetoxins in Marine Sediments

English Abstract:

Harmful algal blooms (HAB), caused by the proliferation of certain biotoxin releasing species of algae, have increased in occurrence, cellular concentration and global distribution over the last 20 years. These toxins persist within the environments of affected areas and act as biomarkers for the spatial and temporal distribution of HAB occurrences. One such suite of biomarkers, known as brevetoxins (PbTx), are produced by the marine dinoflagellate Karenia brevis and are of interest for the reconstruction of the history of red tide HABs. No method currently exists to fully extract and quantify brevetoxins found within marine sediments, a prerequisite for assessment of the environmental conditions that lead to the proliferation of harmful algae using the sedimentary record and other biological proxies.

In this work, a method based on Accelerated Solvent Extraction (ASE) followed by liquid chromatography-mass spectrometry (LC-MS) was optimised for the measurement of brevetoxins in sediments. ASE uses solvents at high temperature and high pressure to maximize extraction efficiency, but also leads to the co-extraction of a large quantity of compounds with properties similar to those of brevetoxins. The result is the formation of a precipitate in the extract that leads to a decrease in brevetoxin recoveries by removing them from solution through flocculation and coagulation. A post-extraction cleaning step was thus developed using solid-phase micro extraction (SPME) fiber probes that minimize sample manipulation and maximize sample throughput. Although we believe that the accelerated solvent extraction of brevetoxins from sediments will be more efficient than conventional extraction methods, more work is required to fully assess the figures-of-merit of the complete ASE-SPME-LC-MS protocol. The preliminary findings are promising, with measured brevetoxin recoveries of 69.1 ± 1.1% for PbTx-3 and 71.9 ± 8.2 % for PbTx-2 using SPME fiber probes, and an absolute detection limit of 1 ng/ml using the optimized LC-MS method.

This newly developed ASE-SPME-LC-MS method, when combined with other sedimentary proxies used to reconstruct paleo-environmental conditions, will further our understanding of the factors that induce the onset of toxic algal blooms and aid in predicting future occurrences.