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    全自动固相萃取-气相色谱-质谱法测定地表水和地下水中9种指示性多氯联苯的含量

    Determination of 9 Indicative Polychlorinated Biphenyls in Surface Water and Groundwater by Gas Chromatography-Mass Spectrometry with Automatic Solid Phase Extraction

    • 摘要: 以题示方法测定地表水和地下水中GB/T 14848-2017规定的9种指示性多氯联苯(PCBs)的含量,并对固相萃取柱、水样酸度、洗脱剂、上样流量等参数进行优化。将地表水或地下水样品充满棕色玻璃瓶,并将水样酸度调节至pH 4。分取1 L水样,加入50 mL丙酮,置于棕色样品瓶中。将上述溶液用注射泵以10 mL·min-1流量过已活化的Bond Elut C18固相萃取柱,以10 mL水淋洗柱子,并用氮气吹扫柱子35 min。用3 mL甲醇和5 mL正己烷清洗注射泵,用7.5 mL正己烷和7.5 mL二氯甲烷洗脱柱子,收集洗脱液并氮吹至近干。加入3,3',4,4'-四氯联苯(PCB77-d6)和2,3,3',4,4',5-六氯联苯-2',6,6'-d3(PCB156-2',6,6'-d3)的混合内标溶液,用正己烷稀释至1.0 mL,使2种内标的质量浓度达到100 μg·L-1。所得溶液进入气相色谱仪,在HP-5MS色谱柱上进行程序升温分离,目标物在配有电子轰击离子源的质谱仪中进行检测,内标法定量。结果显示,9种PCBs标准曲线的线性范围均为1.0~200.0 μg·L-1,检出限(3.143s)为1.1~2.2 ng·L-1;对地表水和地下水样品进行加标回收试验,9种PCBs均未检出,回收率分别为76.4%~102%(地表水)和84.8%~106%(地下水),测定值的相对标准偏差(n=6)分别为0.21%~4.7%(地表水)和0.64%~4.8%(地下水)。

       

      Abstract: The 9 indicative polychlorinated biphenyls (PCBs) specified by GB/T 14848-2017 in surface water and groundwater were determined by the method mentioned by the title. Parameters of solid phase extraction column, water sample acidity, elution solvent and sampling flow were optimized. The surface water or groundwater sample was filled with a brown glass bottle, and its acidity was adjusted to pH 4. An aliquot (1 L) of the water sample was taken, and mixed with 50 mL of acetone. The mixed solution was put into a brown sample bottle, and passed through the activated Bond Elut C18 solid phase extraction column with sampling flow of 10 mL·min-1. The column was rinsed with 10 mL of water, and blown by nitrogen for 35 min. After the syringe pump was washed with 3 mL of methanol and 5 mL of n-hexane, the column was eluted with 7.5 mL of n-hexane and 7.5 mL of dichloromethane, and the eluent was collected and blown to nearly dry by nitrogen. The residue was mixed with the mixed internal standard solution of PCB77-d6 and PCB156-2',6,6'-d3, and diluted with n-hexane to 1.0 mL, making the mass concentration of each internal standard reach to 100 μg·L-1. The obtained solution was introduced into gas chromatograph, and separated on HP-5MS chromatographic column under programmed temperature. The targets were detected by mass spectrometer equipped with an electron impact ion source, and quantitatively analyzed by internal standard method. As found by results that the linear ranges of the standard curves of the 9 PCBs were in the range of 1.0-200.0 μg·L-1, with detection limits (3.143s) in the range of 1.1-2.2 ng·L-1. Test for the spiked recovery was carried out on surface water and groundwater samples, and the 9 PCBs were not detected, giving recoveries in the ranges of 76.4%-102% (surface water) and 84.8%-106% (groundwater). The RSDs (n=6) of the determined values were found in the ranges of 0.21%-4.7% (surface water) and 0.64%-4.8% (groundwater).

       

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