利用半透膜渗透装置富集-超声萃取分析表层沉积物间隙水PCBs的方法

摘要

本文建立了半透膜渗透装置(semi-permeable membrane device,SPMD)富集-超声萃取-凝胶渗透色谱净化-气相色谱法测定沉积物间隙水中多氯联苯(PCBs)的方法.比较了有机溶剂透析法与超声萃取法从膜袋内提取PCBs的回收率,发现超声萃取法在节省时间和溶剂方面有明显优势.应用凝胶渗透色谱分离与净化SPMD提取物,收集11-17min的流出液能达到最佳分离效果.基于此方法测定了大连湾沉积物间隙水中自由溶解态PCBs的含量(Cw-sPMD),同时又分析了沉积物中PCBs的总量(CsED)、间隙水中PCBs的含量(有机碳含量校正法,CW-SED)和间隙水中PCBs的总含量(离心法,CPw).结果表明,CPw值显著高于CW-SED和CW-SPMD值.因此,考虑到生物可利用性,无论采用沉积物中或者间隙水中的PCBs总量进行污染物生态风险评价均会造成风险被高估,建议采用间隙水中可溶解态含量.%A new method for determination of polychlorinated biphenyls (PCBs) in pore water of sediments,including semi-permeable membrane devices (SPMD) enrichment,ultrasonic extraction,cleanup method with gel permeation chromatography,and detection method with gas chromatography,was established.The recoveries of gradients in SPMD tubes extracted by ultrasonic extraction (UE) and organic solvent dialysis (OSD) were compared.Results show that the performance of UE was relatively more advantageous than OSD in term of time and solvent saving.The collection duration of 11-17min was the optimal instrument condition for PCBs collection and separation.Subsequently,the method was applied to monitor the PCBs concentrations in pore water (Cw-sPMD) of the sediments sampled from Dalian Bay,which is considered as the freely dissolved PCBs.Additionally,the total PCBs concentrations in pore water (centrifugation,CPW),of sediment-based aqueous concentrations (calculated using total organic carbon contents in sediment,CW-SED),PCBs contents in sediments (CsED) were simultaneously analyzed.The results suggest that the CPw values of every congeners were much higher than those of CW-SED and CW-SPMD.Consequently,the risk levels were remarkably overestimated using CSED or CPW,thus freely dissolved fraction is recommended instead of total concentrations.