Optimal strategies for determination of free/extractable and total microcystins in lake sediment

The optimization of analytical procedures for the quantification of free and total microcystins (MCs) in natural sediments was systematically examined based on solvent extraction and Lemieux oxidation. In this optimized analytical procedure, a sequential solvent extraction using 50% (v/v) methanol and EDTA-sodium pyrophosphate was selected as the optimal extraction solvent for free MCs analysis, after which the purified extracts and sediment residuals were applied to the optimized Lemieux oxidation for determination of total MCs in lake sediments. The optimized procedures were shown to be efficient and reliable for the routine analysis of both free and total MCs in lake sediment samples, as indicated by the minimal adverse impact of sediment organic matter on the recovery of free MCs and yield of MMPB (2-methyl-3-methoxy-4-phenylbutyric acid). Finally, the developed procedures were applied to field sediment samples collected from Lake Dianchi during a bloom season and seven of thirty samples showed positive results.

Figure optionsDownload as PowerPoint slideHighlights
► An optimized solvent extraction for analysis of free MCs in sediments was proposed.
► Best recovery of free MCs in sediments was found via sequential solvent extraction.
► We further optimized the Lemieux oxidation for analysis of total MCs in sediments.
► The yield of MMPB decreased as the content of sediment organic matter increased.
► Seven of thirty sediment samples showed positive results of MCs in Lake Dianchi.