Objective To establish a rapid method for simultaneous determination of 12 microcystins in surface water with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).
Methods Surface water samples were firstly freeze-thawing for three times, then directly filtered with glass fiber filters for injection. When several or one of the microcystins under the concentration of relevant limit of quantification, GF/C glass fiber was used for filter and an Oasis HLB SPE column was used for the concentration and purifying. The 40% methanol aqueous solution was used for washing; after elution with methanol, equal volume of ultrapure water was added for dilution, and then filtered through synthetic fabric membrane for injection. The separation of the analytes was carried out on an ACQUITY UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm) with gradient elution using bobile phases of 0.2% (v/v) formic acid aqueous solution and methanol mix with acetonitrile at ratio of 2 to 3 containing 0.2% (v/v) formic acid. The 12 microcystins were detected with positive electrospray ionization in multiple reaction monitoring modes, and quantified by external standard methods. Toxicity equivalent factor conversion was used for total toxicity analysis of the detected microcystins.
Results The linear ranges of 12 microcystins were 0.1 – 5.0 ng/mL and the correlation coefficients were greater than 0.995. The limits of detection and quantification were 0.006 – 0.012 μg/L and 0.02 – 0.04 μg/L for SPE method and 0.03 – 0.06 μg/L and 0.1 – 0.2 μg/L for direct injection, respectively. The recoveries were in the range of 83.07% – 108.27% with the relative standard deviations ranging from 0.46% – 12.76% (n = 6). Then the established method was used for the determination of 6 surface water samples and several kinds of microcystins were detected in 4 of the samples.
Conclusion The established method is rapid, simple, sensitive and accurate, and could be applied in determination of 12 microcystins in surface water.
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