| dc.description.abstract | The eutrophication is caused by the over-breeding of plants and algae in the rivers and lakes, which not only causes deterioration of water quality and leading to malodor, but also produces microcystins in various isoforms. Among them, the most common and toxic microcystins is Microcystin-LR (MC-LR). In addition to exposure to aquatic system, humans may also be exposed to microcystins through the food chain, so it is necessary to develop a rapid and reliable method for the determination of microcystin residues in surface water. This study developed a fast, efficient, low-cost and environmentally friendly extraction method to detect two common detected microcystins: MC-LR and MC-YR, in surface water samples. Firstly, using a simple method to produce deep eutectic solvents (DESs), a group of novel “green” solvents, as an extractant, and then Vortex assisted-DES-liquid- liquid microextraction (VA-DES-LLME) was employed for sample preparation and combined with Ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-qTOF-MS) was used for quantitative detection. The parameters of VA-DES-LLME were optimized by multivariate statistic Box-Behnken design (BBD) and analysis of variance (ANOVA). The optimal extraction conditions were: 5 mL of water sample was placed in a sharp-bottomed centrifuge tube, and the solution was made acidic (pH = 2). DES (900 μL) and THF (1.4 mL) were added, and vortexed for 50 s, and then centrifuged at 5000 rpm for 5 minutes. The supernatant was reconstituted with methanol to a volume of 1 mL, and then 2 μL of extractant was directly injected into UHPLC-qTOF-MS for quantitative detection.
The linear ranges of MC-LR and MC-YR was 1-100 μg/L, the coefficient of determination (r2) was above 0.999, and the limit of quantitation (LOQ) of MC-LR and MC-YR were 0.4 and 0.5 ng/mL, respectively. The relative standard deviation (RSD) was less than 11%, and in terms of recovery, the accuracy were between 100% and 126%. This method displayed to be stable and has good reproducibility. Although, for the collected water samples, the content of MC-LR and MC-YR were lower than those of the LOQs of the method. The developed method is sensitive enough to meet the requirement of the World Health organization (WHO) proposed monitoring program. In this program, the maximum allowance concentration in drinking water of microcystins is 1.0 ng/mL | en_US |