A Selective Gas Chromatography-Selected Ion Monitoring Mass Spectrometry (GC-MS/SIM) Method to Determine Polychlorinated Biphenyls in Fuller’s Earth

Polychlorinated biphenyls (PCBs) are carcinogenic to humans and can be found in Fuller’s earth used for the regeneration of used transformer oil. This work describes a highly selective gas chromatographic-selected ion monitoring mass spectrometric method (GC-MS/SIM) for the simultaneous determination of three Aroclor PCB congener mixtures (1242, 1254, and 1260). The separation of the PCBs could be systematically varied by changing the temperature conditions of the chromatographic column. Methods were first selected from the literature, and the resolution of the PCBs was then optimized by adjusting k* (effective retention), a (selectivity), and N (column efficiency), enabling the detection of 83 PCBs in 35 min. The extract of PCBs from Fuller’s earth was obtained by ultrasonication (employing hexane and acetone as solvents) and cleanup with Florisil and was concentrated to about 500 µL. The ions analyzed in SIM mode were divided into groups according to the similarity (m/z) of the PCB fragmentation profiles. The limits of detection (LOD) and quantification (LOQ) were 0.19 and 0.64 µg kg-1, respectively. The method developed was used to determine the PCBs present in Fuller’s earth provided by an electric power company. The mean total PCBs concentration was found 1.9 µg kg-1 in Fuller’s earth.

多氯联苯（Polychlorinated biphenyls, PCBs）对人类具有致癌性，可存在于用于再生废旧变压器油的漂白土中。本研究建立了一种高选择性的气相色谱-选择离子监测质谱法（GC-MS/SIM），可同时测定3种Aroclor型多氯联苯同系物混合物（1242、1254及1260）。通过调节色谱柱的温度条件，可对多氯联苯的分离效果进行系统性调控。本方法首先从公开文献中遴选得到基础方案，随后通过调整有效保留因子k*、选择性因子a以及柱效N对多氯联苯的分离度进行优化，最终实现了35分钟内对83种多氯联苯的同时检测。以正己烷与丙酮为溶剂，通过超声萃取法从漂白土中提取多氯联苯，经佛罗里硅土（Florisil）净化后将提取液浓缩至约500微升。选择离子监测模式下分析的离子依据多氯联苯碎片谱的质荷比（m/z）相似性被划分为若干组别。本方法的检出限（LOD）与定量限（LOQ）分别为0.19与0.64微克每千克。将所建立的方法用于测定某电力公司提供的漂白土样品中的多氯联苯含量，测得漂白土中总多氯联苯的平均浓度为1.9微克每千克。