Development Of The Magnetic Micro-extraction Technology And Its Application In Microcystin Enrichment

In this study, we try to develop some new extraction methods for the trace microcystin analysis in water. The new magnetic solid phase micro-extraction （MSPME） methods coupled with high performance liquid chromatography （HPLC） were developed and used to detect microcystin-LR （MC-LR） and microcystin-RR （MC-RR）. The main results are listed as following:1. The isocratic elution method with low toxicity and low cost was defined for HPLC analysis by investigating the HPLC chromatographic conditions including mobile phase, mobile phase ratio, flow rate, the amount of buffer salts and the injection volume;2. Two new magnetic nanoparticles Fe₃O₄@ NiSiO₃ and Fe₃O₄@ODA@ SiO2 were prepared by hydrothermal synthesis and sol-gel method. The preparation conditions of Fe₃O₄ @ ODA@ SiO2 were optimized. The amount of tetraethoxysilane （TEOS） was 1 mL, octadecylamine dosage was 0.5 g, stirring time was 24 h;3. The new magnetic solid phase micro-extraction technologies were developed correspondingly based on the two above magnetic nanoparticles. The conditions that affected extraction efficiency such as adsorbent dosage, extraction time, elution solvents, the ratio of the eluent, desorption times, desorption time were studied. The magnetic solid phase micro-extraction method coupled with HPLC, was used to enrich and detect trace microcystin in actual water sample. This method consumed less organic solvent and would not cause secondary pollution. The samples could easily to be separated by external magnet. Moreover, the magnetic nanoparticles exhibited good enrichment capacity and selectivity. The quantitative analysis of microcystin could be achieved by this method.Fe₃O₄@NiSiO₃ magnetic particles were prepared for microcystin （MC-LR） enrichment. It was suitable for low concentration, small volume of sample analysis. Microcystin recoveries can up to 81% in pure water samples. For actual water samples analysis, the recovery of 70% was achieved. The limit of detection of the method was 0.011μg/L. The method showed a good linear relationship in the range of 0.25 μg/L-146.5 μg/L with linear correlation coefficient （r） of 0.9991; Fe₃O₄@ ODA@ SiO2 magnetic particles were used to enrich trace microcystin （MC-LR） and microcystin （MC-RR） in large volume of sample analysis. The recoveries of MC-LR and MC-RR were 69.7% and 73.3%, respectively. The detection limit was lower than 1 μg/L. The method of magnetic solid phase micro-extraction combined with high performance liquid chromatography （MSPME-HPLC） was suitable for analysis of trace contaminants in water. It has wide application value and prospects.