提出了全自动QuEChERS结合超高效液相色谱-四极杆-静电场轨道阱高分辨质谱法(UHPLC-Q-Orbitrap HRMS)测定植物源性食品中96种常见除草剂的残留量的方法,同时建立了96种除草剂的精确质量数质谱库,可以实现对非目标化合物的定性筛查。取高水分样品(含水量不小于80%) 10.00 g或低水分样品(含水量小于15%) 5.00 g,茶叶样品则取2.00 g,低水分样品中需加入5 mL水,静置30 min。样品中依次加入10 mg·L^-1内标(±)-氟吡禾灵-d₄溶液50 μL、4 mm氧化锆珠5粒、10 mL体积比为9∶1的含1%(体积分数)乙酸的乙腈溶液-甲苯的混合液和缓冲盐试剂包,在预装有吸附剂(含无水硫酸镁600 mg、C₁₈ 100 mg、石墨化碳黑100 mg)的QuEChERS全自动样品制备系统中涡旋振动和离心。取1 mL上清液,过0.22 μm滤膜,所得溶液在Waters ACQUITY UPLC HSS-T3色谱柱上分离,以含5 mmol·L^-1甲酸铵和0.1%(体积分数,下同)甲酸的甲醇溶液-含5 mmol·L^-1甲酸铵的0.1%甲酸溶液为正离子模式流动相,含5 mmol·L^-1甲酸铵的甲醇溶液-5 mmol·L^-1甲酸铵溶液为负离子模式流动相进行梯度洗脱,采用高分辨质谱平行反应监测(PRM)扫描模式进行定性筛查和内标法定量分析。结果表明,96种除草剂的线性范围均为5.0~100 μg·L^-1,测定下限低至0.01 mg·kg^-1。对猕猴桃、大米、茶叶等3种基质的空白样品进行加标回收试验,回收率为72.9%~105%,测定值的相对标准偏差(n=6)为2.1%~11%。方法用于日常抽检90份不同类型植物源性食品,其中6份样品(大米、小麦和茶叶)中检出除草剂残留。

A method for the determination of residues of 96 common herbicides in plant derived foods was proposed by automatic QuEChERS combined with ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS), meanwhile a mass spectral library for accurate mass numbers of 96 herbicides was established, which could enable qualitative screening of non-target compounds. 10.00 g of a high moisture sample (not less than 80% water content) or 5.00 g (2.00 g for the tea sample) of a low moisture sample (less than 15% water content) was taken, and 5 mL of water was added into a low moisture sample, settling for 30 min. 50 μL of 10 mg·L^-1 internal standard (±)-haloxyfop-d₄ solution, 5 beads of 4 mm zirconia, 10 mL of a mixture of acetonitrile solution containing 1% (volume fraction) acetic acid and toluene at a volume ratio of 9∶1 and buffer salt kit were sequentially added into the sample, and then the mixture were vortexed and centrifuged in QuEChERS automatic sample preparation system pre-loaded with adsorbent (containing 600 g of anhydrous magnesium sulfate, 100 mg of C₁₈, 100 mg of graphitized carbon black). 1 mL of the supernatant was taken and passed through 0.22 μm membrane, and the resulting solution was separated on Waters ACQUITY UPLC HSS-T3 column, using a mixture of methanol solution containing 5 mmol·L^-1 ammonium formate and 0.1%(volume fraction, the same below)formic acid-0.1% formic acid solution containing 5 mmol·L^-1 ammonium formate as the mobile phase in positive ion mode, and a mixture of methanol solution containing 5 mmol·L^-1 ammonium formate-5 mmol·L^-1 ammonium formate solution as the mobile phase in negative ion mode for gradient elution. Parallel reaction monitoring (PRM) scan mode in HRMS was used for qualitative screening and quantitative analysis with internal standard method. As shown by the results, linear ranges of the 96 herbicides were 5.0-100 μg·L^-1, with lower limits of determination low to 0.01 mg·kg^-1. Recovery test was carried out by the standard addition method on the blank samples with three matrices, kiwifruit, rice and tea, giving the results in the range of 72.9%-105%, with RSDs (n=6) of the determined values in the range of 2.1%-11%. The method was used for routine sampling of 90 different types of plant derived foods, of which 6 samples (matrices of rice, wheat and tea) contained herbicide residues.