取5 g豆芽样品,加入100 μg·L^-1混合内标溶液40 μL和含1%(体积分数,下同)乙酸的乙腈溶液10 mL,振荡3 min,超声20 min,离心3 min。重复提取一次,合并上清液,用含1%乙酸的乙腈溶液稀释至25 mL。分取10.00 mL,置于装有QuEChERS吸附剂[100 mg N-丙基乙二胺(PSA)、100 mg C₁₈、800 mg无水硫酸镁]的离心管中,离心3 min,静置5 min。分取5.00 mL上清液于40 ℃氮吹至近干,加入1.00 mL含0.1%(体积分数,下同)甲酸的30%(体积分数)乙腈溶液,复溶后过0.22 μm滤膜,滤液进入超高效液相色谱-三重四极杆质谱仪分析。12种抗生素在ACQUITY UPLC HSS T₃色谱柱(100 mm×2.1 mm,1.8 μm)上用不同体积比的含2 mmol·L^-1甲酸铵的0.1%甲酸溶液和含0.1%甲酸的乙腈溶液的混合液为流动相进行梯度洗脱分离,以电喷雾离子源正离子(ESI⁺)模式电离,以多反应监测(MRM)模式检测,内标法定量。结果显示:12种抗生素的质量浓度均在1.0~250.0 μg·L^-1内和对应的峰面积比呈线性关系,检出限(3S/N)为0.079 6~0.494 μg·kg^-1。按标准加入法进行回收试验,回收率为71.6%~90.9%,测定值的相对标准偏差(n=6)为1.5%~7.6%。方法用于160批豆芽样品(包括黄豆芽、绿豆芽、豆芽苗)的分析,在前二者中检出了恩诺沙星、环丙沙星及甲硝唑,检出量为1.68~992 μg·kg^-1。

An aliquot (5 g) of bean sprout sample was taken, and mixed with 40 μL of 100 μg·L^-1 mixed internal standard solution and 10 mL of acetonitrile solution containing 1% (volume fraction, the same below) acetic acid. The mixture was shaken for 3 min, ultrasonicated for 20 min, and centrifuged for 3 min. The extraction process was repeated once, and the supernatant was combined, and diluted to 25 mL with acetonitrile solution containing 1% acetic acid. An aliquot (10.00 mL) was taken and placed into a centrifuge tube containing QuEChERS adsorbents composed of 100 mg of PSA, 100 mg of C₁₈ and 800 mg of anhydrous magnesium sulfate. The mixture was centrifuged for 3 min and settled for 5 min, and 5.00 mL of the supernatant was taken and blown to near dryness by nitrogen at 40 ℃. The residue was redissolved by 1.00 mL of 30% (volume fraction) acetonitrile solution containing 0.1% (volume fraction, the same below) formic acid, and the solution was passed through a 0.22 μm filter membrane. The filtrate was introduced into the ultra-high performance liquid chromatograph-triple quadrupole mass spectrometer for analysis. Twelve antibiotics were separated on ACQUITY UPLC HSS T₃ column (100 mm×2.1 mm,1.8 μ m) with mixed solutions composed of 0.1% formic acid solution containing 2 mmol·L^-1 ammonium formate and acetonitrile solution containing 0.1% formic acid at different volume ratios by gradient elution, ionized by ESI⁺ mode, detected by MRM mode, and quantified by internal standard method. As shown by the results, linear relationships between values of the mass concentration of 12 antibiotics and the peak area ratio were kept in the range of 1.0-250.0 μg·L^-1, with detection limits (3S/N) in the range of 0.079 6-0.494 μg·kg^-1. Test for recovery was made by standard addition method, giving results of recovery in the range of 71.6%-90.9%, and RSDs (n=6) of the determined values ranged from 1.5% to 7.6%. The proposed method was applied to the analysis of 160 batches of bean sprout samples (including soybean sprouts, mung bean sprouts and bean sprout seedings), and enrofloxacin, ciprofloxacin and metronidazole were detected in the first two samples with detection amounts in the range of 1.68-992 μ g·kg^-1.