加速溶剂萃取-分子筛固相萃取-气相色谱-串联质谱法测定土壤中多氯萘

Determination of polychlorinated naphthalenes in soil using accelerated solvent extraction-molecular sieves solid-phase extraction coupled with gas chromatography-tandem mass spectrometry

新污染物引发的环境和健康风险正逐步受到社会各界的广泛关注,我国第十四个五年规划和2035年远景目标纲要明确“重视新污染物治理”。作为新型的持久性有机污染物,多氯萘(PCNs)在土壤中通常处于痕量水平,一般需要经过多层硅胶柱/氧化铝柱等复杂的净化方法,再结合有效的分析手段才能实现准确测定。关注土壤中多氯萘分离分析方法可以为掌握和监管其在土壤中的污染状况提供技术和方法支持。研究以13X分子筛作为固相萃取吸附剂,评价了其对多氯萘的净化效果。研究发现:使用正己烷作为上样溶剂和淋洗剂,10 mL二氯甲烷/正己烷(2∶15,v/v)为洗脱溶剂,可以实现PCNs与脂类大分子等干扰物的选择性分离,且多氯萘内标的平均回收率为56.1%~88.0%。与凝胶渗透色谱法、弗罗里硅土固相萃取柱以及多层硅胶柱/氧化铝柱相比,13X分子筛对土壤提取液的净化效果优于前两种净化方法,可以获得与多层硅胶/氧化铝柱相近的净化效果(53.0%~117.0%),而且操作更加简单,环境更加友好,分析成本大幅度下降。在此基础之上,建立了加速溶剂萃取-分子筛固相萃取,结合气相色谱-三重四极杆质谱法测定土壤中PCNs的分析方法。PCNs同族体的方法检出限为0.009~0.6 ng/g。采用基质加标法评价了本方法的精密度和准确度,CN-3、13、42、46、52、53、73、75在低、中、高加标水平下的平均加标回收率分别为70%~128%、71%~115%和61%~114%,测定结果的相对标准偏差分别为4.2%~23%、6.5%~31%和4.7%~22%,满足痕量分析的要求且平行性较好。从整个分析流程来看,13X分子筛有望成为新污染物净化的新型固相萃取吸附剂,并在土壤新污染物普查中发挥重要作用。

Emerging pollutants(EPs)are chemical substances that are commonly not regulated and can be detected at low or very low concentrations. However,EPs have triggered special concern because their long-term adverse effects on the environment and human health remain unknown. Most EPs show biological toxicity,environmental persistence,and bioaccumulation.Even at low concentrations in the environment,EPs may pose significant environmental and health risks. Therefore,their treatment has been explicitly included in the14th Five Year Plan for National Economic and Social Development of the People’s Republic of China and the Outline of the Long-term Goals for2035. Soil is a source of pollutants,and its quality is directly related to economic development,ecological security,and people’s livelihood. At present,China’s soil environmental monitoring system is not perfect,and the ability to monitor these new organic pollutants is lagging. Therefore,to strengthen the supervision of construction and agricultural land soil environments,it is essential to strengthen the soil environment monitoring ability for these EPs and establish a reliable,steady,and economic analysis method,including their separation and analysis methods in soil. Polychlorinated naphthalenes(PCNs)have received considerable attention as emerging halogenated compounds. They were listed in Annexes A and C of the Stockholm Convention on persistent organic pollutants(POPs)in2015because of their persistence,multimedia fate,and toxicity. PCNs have now been detected in the surrounding soils. Owing to their trace levels in complex soil,high requirements have been put forward for the pretreatment and instrument analysis of PCNs. This study aims to develop a new method for the selective purification of PCNs in soil,which can not only effectively remove lipids and other interferences in soil but also effectively reduce time,labor,and material costs in the pre-treatment process. Based on the physicochemical properties of the13X molecular sieve,it was explored to purify soil-extracts as solid-phase extraction(SPE)sorbents. With n-hexane as the loading and rinsing solvent, 10mL of a dichloromethane/n-hexane mixture(2 ∶ 15,v/v)was used to elute the PCNs. Moreover,selective separation of target substances from lipid macromolecules and other interferences could be achieved simultaneously. For the selective separation of PCNs,the average recovery of the internal standard could reach56. 1% to88. 0%.13X molecular sieves are superior to gel permeation chromatography(GPC)and Florisil SPE,and they exhibit good cleanup efficiency similar to a multilayer silica gel/alumina column(53. 0%-117. 0%). Although the obtained recoveries are not as high as those obtained with a multilayer silica gel/alumina column, 13X molecular sieves have advantages in terms of simple operation,environmental friendliness,and low cost.Based on these fundamental experiments,accelerated solvent extraction was used to extract targets in soil,molecular sieves were used as SPE sorbents for purification,and GC-MS/MS was employed for PCN analysis. This method was developed as a systematic analytical method for PCNs determination. The method detection limits(MDLs)for PCN homologs were in the range of0. 009-0. 6ng/g. The precision and accuracy of the method were evaluated using spiked matrices. At three spiked levels(4, 10,and18ng),the recoveries of PCNs(CN-3, 13,42, 46, 52, 53, 73,and75)were70%-128%, 71%-115%,and61%-114%,respectively,and the corresponding relative standard derivations were4. 2%-23%, 6. 5%-31% and4. 7%-22%.Thus,this method meets the requirements of trace analysis and shows acceptable parallelism,sensitivity,accuracy,and precision,thus being feasible for the analysis of emerging pollutant.The method is expected to play an important role in sample pretreatment in the future,especially for the nationwide investigation of soil pollution.