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    气相色谱-串联质谱法测定土壤中64种半挥发性有机物的含量

    Determination of 64 Semi-Volatile Organic Compounds in Soil by Gas Chromatography-Tandem Mass Spectrometry

    • 摘要: 取经冷冻干燥处理并过筛后的土壤样品10 g,加入10 g硅藻土,混匀,加入2-氟联苯、4,4′′-三联苯-d14的质量浓度为10 mg·L−1的替代物混合标准溶液50 µL,置于加压流体萃取仪中,以体积比1∶1的正己烷-丙酮混合溶液为萃取溶剂,在温度100 ℃、压力10.34 MPa下静态萃取8 min,循环萃取2次。萃取液于30 ℃氮吹浓缩至近干,用正己烷定容至1.0 mL。在活化好的硅酸镁小柱中加入0.5 g铜粉,再加入上述待净化液,保持5 min,用5 mL体积比2∶8的异丙醇-正己烷混合溶液洗涤浓缩装置,洗涤液一并转入硅酸镁小柱,依次用10 mL体积比1∶9的丙酮-正己烷混合溶液、8 mL体积比2∶8的异丙醇-正己烷混合溶液洗脱,收集洗脱液,于30 ℃氮吹浓缩至0.80 mL,加入萘-d8、菲-d10、䓛-d12、苝-d12和十氯联苯的质量浓度为10 mg·L−1的混合同位素内标溶液50 µL,用正己烷定容至1.0 mL,采用气相色谱-串联质谱法测定溶液中64种半挥发性有机物的含量。在色谱分析中,以HP-5MS色谱柱为固定相,在柱升温程序下分离;在质谱分析中,以电子轰击离子源电离,多反应监测模式检测,内标法定量。结果显示,64种目标物的质量浓度均在20~1 000 µg·L−1内与其内标质量浓度的比值和对应的定量离子对响应值与内标定量离子对响应值的比值呈线性关系,检出限(3.143s)为0.19~2.89 μg·kg−1。按照标准加入法进行回收试验,回收率为63.4%~125%,测定值的相对标准偏差(n=6)为1.4%~14%。按照试验方法分析4份土壤样品,64种目标物均有检出,检出量为3.41~1 606 952 μg·kg−1

       

      Abstract: The soil samples (10 g) that had been freeze-dried and sieved were taken, and 10 g of diatomaceous earth was added. The mixture was mixed uniformly and 50 µL of surrogate standard solution including 2-fluorobiphenyl and 4,4′′-triphenyl-d14 with mass concentration of 10 mg·L−1 was added. The mixture was placed in the pressurized fluid extractor, static extraction was performed twice with the mixed solution of n-hexane and acetone at volume ratio of 1∶1 as extractant at temperature of 100 ℃, pressure of 10.34 MPa, and extraction time of 8 min. The extract was concentrated to near dryness by nitrogen at 30 ℃, and made its volume up to 1.0 mL with n-hexane. 0.5 g of copper powder was added to the activated magnesium silicate cartridge, followed by the addition of the aforementioned solution to be purified, and the mixture was allowed to stand for 5 min. The concentration device was washed by 5 mL of the mixed solution of isopropanol and n-hexane at volume ratio of 2∶8, and the washing solution was transferred to the magnesium silicate cartridge together. Elution was carried out sequentially with 10 mL of the mixed solution of acetone and n-hexane at volume ratio of 1∶9 and 8 mL of the mixed solution of isopropanol and n-hexane at volume ratio of 2∶8. The eluate was collected and concentrated to 0.80 mL by nitrogen at 30 ℃. 50 µL of mixed isotope internal standard solution including naphthalene-d8, phenanthrene-d10, chrysene-d12, perylene-d12, and decachlorobiphenyl with mass concentration of 10 mg·L−1 was added, and the mixture was made its volume up to 1.0 mL with n-hexane. The 64 semi-volatile organic compounds in the solution was determined by gas chromatography-tandem mass spectrometry. In chromatographic analysis, HP-5MS column was used as the stationary phase for separation under the column heating program. In mass spectrometric analysis, electron impact ion source was used for ionization, multiple reaction monitoring mode was used for detection, and internal standard method was used for quantification. As shown by the results, linear relationships between the ratios of the corresponding quantitative ion pair response values to the internal standard quantitative ion pair response values and the ratios of mass concentrations of 64 targets to their internal standards were kept in the range of 20‒1 000 µg·L−1, with detection limits (3.143s) in the range of 0.19‒2.89 μg·kg−1. Test for recovery was made by the standard addition method, giving results in the range of 63.4%‒125%, with RSDs (n=6) of the determined values in the range of 1.4%‒14%. This method was applied to the analysis of 4 soil samples, and 64 targets were all detected, with the detection amounts in the range of 3.41‒1 606 952 μg·kg−1.

       

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