基于柑橘皮渣纳米多孔碳分散固相萃取-气相色谱法 测定果蔬中14种有机磷农药残留

以废弃柑橘皮渣为碳源,通过ZnCl2活化后高温煅烧制备了纳米多孔碳材料(NPC),将其作为吸附剂,建立了分散固相萃取净化、气相色谱法测定果蔬中有机磷农药残留的方法.扫描电子显微镜(SEM)、X射线衍射(XRD)、傅立叶红外光谱(FT-IR)、拉曼光谱及氮气吸附分析(BET)等表征显示,NPC是无定形的多孔碳材料,孔径大小为0~15 nm,比表面积和孔体积分别为1243 m2/g和1.28 cm3/g.以果蔬中14种有机磷类农药为分析对象,考察了吸附剂的用量和净化时间,并将NPC与商业化材料N-丙基乙二胺(PSA)、十八烷基硅胶键合相(C18)和石墨化碳黑(GCB)进行了对比.结果表明,NPC最佳使用量为0.01 g,净化时间只需2 min.NPC成本远低于C18、PSA和GCB,因具有丰富的孔道结构,NPC净化效果显著优于3种商业化材料.在最优条件下,14种有机磷农药在0.02~1.0 mg/L范围内的线性关系良好(R2>0.99),检出限(S/N=3)为0.63~5.30μg/kg.3个添加水平下的平均回收率为71.3%~114.7%,相对标准偏差(RSD)为0.9%~12.9%.本方法操作简便、快速、成本低,在果蔬样品前处理中具有广阔的应用前景.     

加速溶剂萃取-凝胶色谱净化-气质联用测定土壤中15种有机氯农药残留的方法研究

建立了加速溶剂萃取-凝胶色谱净化-气质联用同时测定土壤中15种有机氯农药的分析方法。优化了凝胶色谱(GPC)净化的条件,比较了凝胶色谱净化及浓硫酸净化法对15种有机氯回收率的影响。结果表明,采用GPC净化能够有效避免浓硫酸净化对氯丹、异狄氏剂、硫丹、甲氧滴滴涕等农药回收率的影响,GPC净化的最佳收集时间为10~15 min,15种有机氯农药的回收率为56%~122%。15种有机氯农药在0.03~6.0 mg/L范围内具有较好的线性,相关系数达0.999以上,方法的检出限为0.1~5.0μg/kg,定量下限为0.4~16.0μg/kg。采用该方法对实际样品进行加标回收率实验,土壤样品的加标回收率为68%~122%,相对标准偏差为1.2%~5.9%。该方法简单、快捷、灵敏度高,已用于实际土壤样品的检测。     

液相色谱-离子阱-飞行时间串联质谱快速筛查蔬菜中188种农药残留

建立了蔬菜中188种农药多残留的液相色谱-离子阱-飞行时间串联质谱(LC-MS-IT-TOF)检测方法。样品以乙酸-乙腈(1∶99)提取,旋转蒸发近干后经活性炭和N-丙基乙二胺(PSA)复合固相萃取柱(CarbonGCB/PSASPE)净化,乙腈-甲苯(3∶1)洗脱,氮吹至干,甲醇定容后上机测定。除啶虫脒、联苯三唑醇、速灭磷的线性范围为10～250μg/L外,其余农药的线性范围均为5～250μg/L,相关系数均大于0.987,检出限为0.02～5.50μg/kg。在西兰花空白基质中进行5、10μg/kg两水平的加标回收实验,平均回收率分别为18%～105%、26%～130%,相对标准偏差分别为5.8%～30.1%、2.8%～22.8%。     

固相萃取气相色谱-质谱法测定蔬菜中含氮杂环农药残留

建立了固相萃取（SPE）气相色谱-质谱（GC-MS）同时测定蔬菜中敌菌灵、噻菌灵、氟虫腈和噻嗪酮4种含氮杂环农药残留量的分析方法.蔬菜样品用乙腈匀浆提取后经弗罗里硅（Florisil）固相萃取柱净化.采用GC-MS检测,在选择离子检测（SIM）模式下以特征离子定量,用全扫描（SCAN）方法确证.方法具有良好的线性关系（R≥0.9953）和重现性（峰面积RSD≤9.1%）,最低检出限（S/N=3）在3.6~1.8×10-4μg/mL之间,4种农药添加回收率在76.1%~116.4%之间,RSD≤9.8%,用于实际样品菜心的检测,结果满意.方法操作简单,灵敏度高,可作为测定各种蔬菜基质中含氮杂环农药残留量的确证方法.     

Ultrasound‐assisted dispersive liquid–liquid microextraction coupled with capillary gas chromatography for simultaneous analysis of nine pyrethroids in domestic wastewaters

A simple and rapid ultrasound‐assisted dispersive liquid–liquid microextraction method coupled with GC‐flame ionization detection was developed for simultaneous determination of nine pyrethroids in domestic wastewater samples. An ultrasound‐assisted process was applied to accelerate the formation of the fine cloudy solution using small volume of disperser solvent, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters affecting the extraction efficiency were investigated, including the type and volume of extraction solvent and disperser solvent, extraction and ultrasonic time. Good linearity was obtained for all analytes in the range of 0.8–100 μg/L with the correlation coefficient (r²)≥0.998. The recoveries at three spiking levels ranged from 75.3 to 101.2% with the RSD less than 8.7% (n=5). Under the optimum condition, the enrichment factors for the nine pyrethroids ranged from 728‐ to 1725‐fold. This method offered a good alternative for routine analysis due to its simplicity and reliability.     

Different responses of E:Z‐isomers of pesticides in liquid chromatography–electrospray ionization–mass spectrometry

The mass spectrometric behavior of four pairs of stereoisomers was investigated by liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI–MS). The E‐ and Z‐isomers of the pesticides chlorfenvinphos, dimethomorph, mevinphos and phosphamidon—each with one double bond—were chosen for this study. The MS response of the individual isomers was investigated by infusing the isomers individually into the MS or after the separation of isomer mixtures via high‐performance liquid chromatography(HPLC). In the case of dimethomorph, the same MS response was found for the two isomers. In contrast to that, the individual isomers of chlorfenvinphos, mevinphos and phosphamidon showed different MS response both in the single ion monitoring (SIM) mode in single quadrupole MS and multiple reaction monitoring (MRM) mode in tandem MS. The MS response of the isomers partly depends on (1) the declustering potential of the precursor ion in the SIM mode, (2) the selected transition and (3) the collision energy in the MRM mode. Consequently, quantification by summation of the peak areas of the isomers is inaccurate due to over‐ or underestimating of one of the stereoisomers. Accurate quantitative results can only be achieved when the compound‐specific MS parameters are separately determined for each isomer. This can be done by using pure isomers or by the determination of the MS parameters after HPLC separation and the measurement of the actual isomer ratio with an independent technique. Copyright © 2010 John Wiley & Sons, Ltd.     

Low-density extraction solvent-based solvent terminated dispersive liquid–liquid microextraction combined with gas chromatography-tandem mass spectrometry for the determination of carbamate pesticides in water samples

A simple and fast method of low-density extraction solvent-based solvent terminated dispersive liquid–liquid microextraction (ST-DLLME) was developed for the highly sensitive determination of carbamate pesticides in the water samples by gas chromatography-tandem mass spectrometry (GC-MSMS). After dispersing, the obtained emulsion cleared into two phases quickly when an aliquot of acetonitrile was introduced as a chemical demulsifier into the aqueous bulk. Therefore, the developed procedure does not need centrifugation to achieve phase separation. It was convenient for the usage of low-density extraction solvents in DLLME. Under the optimized conditions, the limits of detection for all target carbamate pesticides were in range of 0.001–0.50 ng mL⁻¹ and the precisions were in the range of 2.3–6.8% (RSDs, 2 ng mL⁻¹, n = 5). The proposed method has been successfully applied to the analysis of real water samples and good spiked recoveries over the range of 94.5–104% were obtained.     

Development of a simple extraction and clean-up procedure for determination of organochlorine pesticides in soil using gas chromatography–tandem mass spectrometry

A procedure based on QuEChERS extraction and a simultaneous liquid–liquid partition clean-up was developed. The procedure involved extraction of hydrated soil samples using acetonitrile and clean-up by liquid–liquid partition into n-hexane. The hexane extracts produced were clean and suitable for determination using gas chromatography–tandem mass spectrometry (GC–MS/MS). The method was validated by analysis of soil samples, spiked at five levels between 1 and 200 μg kg⁻¹. The recovery values were generally between 70 and 100% and the relative standard deviation values (%RSDs) were at or below 20%. The procedure was validated for determination of 19 organochlorine (OC) pesticides. These were hexachlorobenzene (HCB), α-HCH, β-HCH, γ-HCH, heptachlor, heptachlor epoxide (trans), aldrin, dieldrin, chlordane (trans), chlordane (cis), oxychlordane, α-endosulfan, β-endosulfan, endosulfan sulfate, endrin, p,p′-DDT, o,p′-DDT, p,p′-DDD and p,p′-DDE. The method achieved low limits of detection (LOD; typically 0.3 μg kg⁻¹) and low limits of quantification (LOQ; typically 1.0 μg kg⁻¹). The method performance was also assessed using five fortified soil samples with different physico-chemical properties and the method performance was consistent for the different types of soil samples. The proposed method was compared with an established procedure based on Soxtec extraction. This comparison was carried out using six soil samples collected from regions of Pakistan with a history of intensive pesticide use. The results of this comparison showed that the two procedures produced results with good agreement. The proposed method produced cleaner extracts and therefore led to lower limits of quantification. The proposed method was less time consuming and safer to use. The six samples tested during this comparison showed that soils from cotton growing regions contained a number of persistent OC residues at relatively low levels (<10 μg kg⁻¹). These residues were α-HCH, γ-HCH, heptachlor, chlordane (trans), p,p′-DDT, o,p′-DDT, p,p′-DDD, p,p′-DDE, β-endosulfan and endosulfan sulfate.     

Group-specific fragmentation of pesticides and related compounds in liquid chromatography–tandem mass spectrometry

Current strategies in the LC–MS analysis of pesticides and related compounds in environmental samples, fruits and vegetables, and biological samples mostly rely on the selection of appropriate precursor/product-ion combinations (transitions) for selected reaction monitoring (SRM), often based on automated parameter optimization and selection of the transition. Such a procedure does not require any information on the type of fragmentation reaction involved in the generation of the product ion from the selected precursor ion. However, such information does become important in untargeted screening for unknown contaminants in environmental and food samples, which are generally based on a combination of high-resolution mass spectrometry and (multistage) tandem mass spectrometry. With this in mind, the group-specific fragmentation behaviour has been studied for six classes of pesticides and herbicides, i.e., triazines, organophosphorous pesticides, phenylurea herbicides, carbamates, sulfonylurea herbicides, and chlorinated phenoxy acid herbicides. When relevant, some comparison was made between fragmentation of protonated molecules in MS–MS and of molecular ions generated by electron ionization in GC–MS.     

荧光法快速检测有机磷农药残留总量

在pH4.60的B-R缓冲溶液中,中性红(NR)与一定浓度的十二烷基苯磺酸钠(SDBS)发生荧光增强反应,在该体系中加入有机磷农药后,在激发波长560 nm,发射波长604 nm处体系的荧光强度明显降低,且降低程度与有机磷农药的加入量呈良好的线性关系,其线性范围和检出限分别为0.024~0.40 mg/L,0.014 mg/L。据此建立了测定有机磷农药残留总量的新方法。方法已用于面粉和土壤中有机磷农药残留总量的检测,回收率在92.0%~100.5%之间,RSD在1.1~1.9%之间。