羰基铁粉掺杂整体柱萃取-在线热解吸进样气相色谱-串联质谱法分析茶叶样品中拟除虫菊酯类农药残留

Thermal desorption sampling-gas chromatography-tandem mass spectrometry with a carbonyl-iron powder composite silica monolithic column for enrichment and determination of pyrethroid pesticide residues in tea samples

制备了羰基铁粉掺杂硅胶整体柱,用于拟除虫菊酯类农药残留萃取,并与气相色谱-串联质谱(GC-MS/MS)法联用,建立了在线富集、热解吸GC-MS/MS测定茶叶样品中拟除虫菊酯类农药残留方法。研究将端羟基聚二甲基硅氧烷共价键合到SiO2网络表面,并同时键合羰基铁粉。将目标分析物吸附并浓缩在聚二甲基硅氧烷位点上后,利用羰基铁粉的高频感应加热特性成功实现了GC-MS/MS直接气体进样并可达到快速、均匀解吸的目的。实验结果表明,在最佳条件下,本方法的富集倍数可达到约1000倍。拟除虫菊酯类农药残留的检出限为3.8~7.5μg/kg,相对标准偏差为3.2%~6.8%(n=6)。该方法的提取回收率为97.7%~110.5%,相关系数≥0.9960。该法的吸附容量大,在电磁感应的条件下进行热脱附继而直接与GC-MS结合实现在线分析以及无溶剂洗脱。与常规固相微萃取(SPME)方法相比,该方法具有富集因子高、整体柱吸附容量大、可重复使用、自动化程度高、普适性好等优点。在样品前处理及复杂基质中农药残留的提取方面具有重要的研究意义。

Long-term exposure to pyrethroid insecticides is detrimental to the nervous system,reproductive system,and immune system in humans.Therefore,enrichment detection of pyrethroid pesticides is imperative.In this study,a novel carbonyl-iron powder composite silica monolithic column was first prepared for the enrichment of pyrethroid pesticide residues in tea samples.Then,the target analytes were thermally desorbed and online-injected into a gas chromatography-tandem mass spectrometry(GC-MS/MS)system.In the present method,hydroxy-terminated polydimethylsiloxane(PDMS)was covalently bonded to the surface of the SiO2 network and subsequently bonded with the carbonyl-iron powder.After the target analytes were adsorbed and concentrated in the PDMS spots,high-frequency induction heating was used for GC-MS/MS sampling.Under the optimal conditions,the detection limits of the pyrethroid pesticide residues were 3.8 to 7.5μg/kg,and the relative standard deviation was 3.2%to 6.8%(n=6).The extraction recovery ranged from 97.7%to 110.5%,and the correlation coefficient was≥0.9960.In addition,the enrichment factor could reach 1000 times.PDMS materials show excellent adsorption properties for non-polar solutes.In our experiment,carbonyl iron powder-bonded monolithic columns were prepared on the basis of stir bar sorptive extraction(SBSE).Carbonyl iron powder magnetic particles were evenly implanted into the inorganic-organic hybrid cassia material for realizing rapid and uniform desorption upon electromagnetic induction heating.Under the premise of perfectly integrating the technical advantages of SBSE and solid-phase microextraction(SPME),the electromagnetic induction characteristics of carbonyl iron powder can be exploited for thermal desorption and directly combined with GC-MS to facilitate online analysis and solvent-free elution.Compared with the conventional SPME method,the proposed method has the advantages of high enrichment factor,large adsorption capacity of the column,reusability,high degree of automation,and good universality.This method has high significance for sample preparation and for the extraction of pesticide residues in complex matrices.