反复冻融-固相萃取-液相色谱串联质谱法测定蓝藻中5种微囊藻毒素

Determination of Five Microcystins in Cyanobacteria by Liquid Chromatography Tandem Mass Spectrometry Using Freezing-thawing and Solid Phase Extraction

建立了反复冻融-固相萃取-液相色谱串联质谱法测定蓝藻中5种微囊藻毒素（MCs）的方法。水中蓝藻经0.45μm混合纤维滤膜过滤分离,采用3次-20℃/37℃冻融,2次5mL75%甲醇提取,末端封尾的C18固萃小柱浓缩和10mL5%甲醇净化,选择C18色谱柱（50mm×2.1mm,1.7μm）,以0.1%甲酸和0.1%甲酸-乙腈为流动相,梯度洗脱分离,采用多反应监测模式,外标法定量分析。5种MCs在1.25～50μg/L内线性良好,相关系数大于0.995,仪器精密度（RSD）为3.0%～11.5%,方法检出限为0.05～0.2ng。在1、5和50ng的加标水平下,MCs的回收率分别为63.7%～100.4%（RSD为5.5%～13.1%）、72.6%～85.7%（RSD为3.1%～6.6%）和72.5%～80.5%（RSD为2.6%～8.3%）。应用本方法对南方某饮用水源地,开展连续5个月的胞内和胞外MCs监测。

A method was developed for simultaneous determination of five microcystins （MCs） in Cyanobacteria by liquid chromatography Tandem mass spectrometry（LC-MS/MS） using freezing-thawing and solid phase extraction （SPE）. Cyanobacteria in environmental water was collected by 0.45 μm hybrid filter and extracted with two times of 5 mL 75% methanol after three times of -20 ℃/37 ℃ freezing-thawing. The extract was concentrated by end-capped Cls SPE cartridge with a clean-up by 10 mL 5% methanol. Five MCs were detected by LC-MS/MS with multiple reaction monitoring and external standard method. Gradient elution was employed with a mobile phase consisting of acetonitrile with 0. 1% formic acid and water with 0. 1% formic acid on C18 column （50 mm×2. 1 mm, 1.7 μm）. The method showed good linear correlations in a range of 1.25-50 μg/L with correlation coefficients greater than 0. 995. RSD and LOD were 3.0%-11.5% and 0. 05 - 0. 2 ng, respectively. Recovery of three spiked levels （ 1, 5 and 50 ng） for five MCs were 63.7%-100.4% （RSDS. 5%-13.1%）, 72.6% -85.7% （RSD 3. 1% -6.6%） and 72.5% -80.5% （RSD 2.6%-8.3% ） , respectively. The proposed method was applied in the detection of intracellular and extracellular MCs in one drinking water source of South China from August to December.