Synthesis of magnetic core-shell Fe 3 O 4 @PDA@Cu-MOFs composites for enrichment of microcystin-LR by MALDI-TOF MS analysis.

Microcystin-LR (MC-LR) is a toxin released from cyanobacteria in eutrophicated water. MC-LR is the most abundant and the most toxic among microcystins. In this work, core-shell structured copper-based magnetic metal-organic framework (Fe 3 O 4 @PDA@Cu-MOFs) composites were synthesized via a solvothermal reaction and a sol-gel method. The Fe 3 O 4 @PDA@Cu-MOFs composites showed ultra-high surface area, strong magnetic response and outstanding hydrophilicity. The Fe 3 O 4 @PDA@Cu-MOFs composites combined with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) were used to analyse the content of MC-LR in real water samples. Under the optimised conditions, our proposed method exhibited good linearity within a concentration range of 0.05-4 μg L -1 and good detection even at low limits (0.015 μg L -1 ). The method was also successfully applied to analyse traces of MC-LR with quantitative recoveries for the real water samples in the range from 98.67% to 106.15%. Furthermore, it was characterized by high sensitivity, short operation time, being environmental friendly and having the ability to analyse other pollutants in the environment.