Abstract: A method has been developed for the simultaneous determination of nine microcystins (MCs) in surface water by solid phase extraction-ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (SPE-UPLC-ESI-MS/MS). The samples were enriched and purified by an HLB solid phase extraction column. The separation was performed on an ACQUITY UPLCTM system with a BEH C18 column with the gradient elution of acidified acetonitrile and water (both containing 0.1%(v/v) formic acid). The nine MCs were determined in the modes of electrospray positive ionization (ESI+) and multiple reaction monitoring (MRM). Good linearities were observed in the ranges of 0.1~50 μg/L for MC-RR and 0.5~100 μg/L for the others with correlation coefficients over 0.9990 and the limits of detection for the nine MCs were in the range of 0.1~0.5 ng/L. The recoveries were in the range of 75.8%~109% in the three spiked levels of 1.0, 10 and 50 μg/L with the relative standard deviations of 0.49%~10.0%. The method is characterized by high sensitivity and precision, extensive analytical range and quick analytical rate. This method was used in the analysis of water samples from two reservoirs situated in Hangzhou, and the 3 and 8 microcystins were detected individually.

Key words: microcystins, surface water, ultra performance liquid chromatography-electro- spray ionization tandem mass spectrometry (UPLC-ESI-MS/MS), solid phase extraction (SPE)