An analytical method was developed for the simultaneous and rapid determination of seven microcystins in fish meat by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with pass-through solid phase extraction (SPE). The samples were extracted with methanol-water (90:10, v/v) after heat treatment by water bath at 80℃, and then cleaned up with an Oasis PRiME HLB pass-through SPE column. The samples were analyzed directly on a Waters XSelect HSS T3 column using 0.1% (v/v) aqueous formic acid and acidified acetonitrile (0.1% formic acid, v/v) as mobile phases. Qualitative and quantitative analysis of the analytes was carried out under the multiple reaction monitoring mode with positive electrospray ionization. The matrix matching external standard method was used for quantitation analysis. To solve the problem of parent ion selection of the microcystins, the ionization characteristics of microcystins were evaluated under different mobile phase conditions. Finally, the results showed that the acid could promote the intensity of the doubly charged ions significantly. The calibration curves were linear well in the corresponding concentration ranges, with correlation coefficient ≥ 0.99. The limits of quantification ranged from 0.30 to 2.0 μ g/kg. The average spiked recoveries for the seven microcystins were between 70.6% and 96.1% with the relative standard deviations of 3.4%-9.6%. The proposed method is sensitive, accurate, and efficient. It is applicable for the determination of microcystins in fish meat.
Keywords: doubly charged ions; fish meat; liquid chromatography-tandem mass (LC-MS/MS); microcystin (MC); pass-through solid-phase extraction.