速冻蔬菜中氯氰菊酯残留量的测量不确定度评定

依据GB/T 5009.146-2003《植物性食品中有机氯和拟除虫菊酯类农药多种残留的测定》方法,对速冻蔬菜中氯氰菊酯残留量的测量不确定度进行分析和评定。该测量过程所产生的测量不确定度主要来源于气相色谱仪引入的测量不确定度,其次是氯氰菊酯标准工作溶液引入的测量不确定度。标准溶液引入的测量不确定度则主要来源于标准溶液的稀释过程所产生的测量不确定度。     

气相色谱法分析氯氰菊酯异构体

比较了DB-1和HP-5石英毛细管柱在不同柱流速、柱温下对氯氰菊酯异构体的分离效果,表明采用DB-1石英毛细管柱(30m×0.25mmi.d.,0.25μm)较好,柱温为240℃,柱流速为12cm/s,分析时间40min。该分析方法重现性好,分析结果准确、可靠。     

Use of stable carbon isotope ratios to determine the source of cypermethrin in so-called natural plant extract formulations used for organic farming

Some natural plant extract formulations (NPEFs, also referred to as essential oils) used in organic farming have been shown to contain synthetic pesticides. We obtained samples of four NPEFs (Muso, Hekiro, Kensogen-Ten, and Nurse Green) that were contaminated with the synthetic pyrethroid cypermethrin, and we used gas chromatography coupled with combustion, cryofocusing, and isotope ratio mass spectrometry to determine the stable carbon isotope ratios (δ¹³C) for the cypermethrin in the four NPEF samples, as well as in ten cypermethrin reagents and two commercial pesticide formulations (Agrothrin emulsion and Agrothrin water-dispersible powder). Our goal was to identify the source of the cypermethrin in the NPEFs. Cryofocusing markedly sharpened the cypermethrin peak and thus improved the accuracy and precision of the determined δ¹³C values. The δ¹³C values (±?SD) of the 16 cypermethrin samples ranged from ?28.3?±?0.2 to ?24.5?±?0.2?‰. Surprisingly, the four NPEFs showed similar δ¹³C values (?26.8 to ?27.3?‰), suggesting that the cypermethrin in all the samples came from the same source (either the same chemical reaction or the same primary material). This possibility was supported by previously published results. In addition, the δ¹³C values of the two commercial pesticides were similar to the values for the NPEFs, suggesting that the commercial pesticides had been diluted and sold as NPEFs.     

辛硫磷和氯氰菊酯复配制剂的高效液相色谱分析

提出了同时测定辛硫磷和（高效）氯氰菊酯含量的主同效液相色谱分析方法。采用正相柱、２３５ｎｍ紫外检测，石油醚／乙腈流动相系统实现辛硫磷及其杂质与（高效）氯氰菊酯异构体的良好分离。     

气相色谱法测定地表水中拟除虫菊酯类农药残留

建立了气相色谱检测地表水样中痕量氯氟氰菊酯、氯氰菊酯、氰戊菊酯和溴氰菊酯农药残留的分析方法。水样经环己烷液液萃取、无水硫酸钠过滤,再用N-丙基乙二胺和无水硫酸镁净化,用氮气吹干浓缩,再用正己烷溶解,离心分离后取上清液进样,以气相色谱法测定4种拟除虫菊酯的含量。4种拟除虫菊酯化合物的质量浓度在5~200μg/L范围内与色谱峰面积成良好的线性关系,相关系数均大于0.999,方法检出限为0.03~0.09μg/L,模拟水样的平均加标回收率为98.0%~104.5%,相对标准偏差为0.89%~6.44%(n=6)。该方法操作方便、快速,结果准确、可靠,有机溶剂用量少,适用于水中拟除虫菊酯类农药残留的测定。     

Risk assessment,development and validation of a GC-ECD-based method for the quantification of cypermethrin from green pea

The present work describes the persistence, dissipation behaviour, half-life, risk assessment and novel gas chromatography method for the residue estimation of cypermethrin in green pea by spraying cypermethrin 10EC at 50 g a.i. ha⁻¹ at fruiting stage followed by another application at a 10 day interval. The sample extraction and cleanup was followed bya modified quick, easy, cheap, effective, rugged, and safe method, and the residues of cypermethrin were determined using a validated gas chromatography method. The initial deposits were found to be 1.21 mg kg⁻¹ following the application of insecticide at 50 g a.i. ha⁻¹. Cypermethrin residues declined to below the detection limit of 0.05 mg kg⁻¹ after 15 days at the recommended dosage. The half-life of cypermethrin was 2.66 days at 50 g a.i. ha⁻¹. For risk assessment studies, the waiting period of 15 days is recommended as safe for consumption for the insecticide. The GC-ECD method was validated according to the SANTE guidelines by various analytical parameters including linearity, accuracy, detection and quantification limits. The developed method is simple, selective and repeatable, and can be used for the standardization of pesticides on fruits and vegetables.     

辛硫磷和氯氰菊酯的大口径毛细管气相色谱定量分析研究

对辛硫磷和氯氰菊酯的复配农药——２０％辛氯乳油进行了气相色谱定量分析的研究。以甲基对硫磷为内标，使用大口径毛细管柱，采用快速程序升温、高载气流速等手段，解决了辛硫磷高温易分解与氯氰菊酯色谱流出温度高的矛盾。在相同的色谱条件下对二者进行定量分析，变异系数分别为０．６７％和１．０％。方法简便、快速、准确。     

超声波-二氧化钛光催化耦合法降解高效氯氰菊酯

采用超声波-TiO2光催化耦合法降解高效氯氰菊酯,考察了高效氯氰菊酯初始浓度、降解时间、溶液pH、催化剂用量等对高效氯氰菊酯农药残留的降解效果,并利用水果进行了实物模拟.结果表明:利用超声波-TiO2光催化耦合法能够有效地降解高效氯氰菊酯农药残留.在弱酸环境中,当纳米TiO2投放量为1.2g/L时,经2h超声催化降解,不同浓度的高效氯氰菊酯农药稀释液均被有效降解,降解率最高可达98.3%.     

Analysis of cypermethrin residues and its main degradation products in soil and formulation samples by gas chromatography-electron impact-mass spectrometry in the selective ion monitoring mode

A fast, simple and inexpensive sample preparation method based on the matrix solid-phase extraction (SPE) technique is proposed for the isolation of cypermethrin and its metabolite residues from soils. Both the extraction and clean-up procedures were carried out in two steps and target compounds were determined by gas chromatography coupled with electron-impact mass spectrometry (GC-EI/MS). The characteristic ions and fragmentation mechanism of cypermethrin were evaluated by electron impact ionization mass spectrometry (EI/MS). After the optimization of different parameters, such as the extraction solvent, the pesticide was extracted from the matrix with methanol/acetone in a Soxhlet extractor, cleaned up on a Florisil column by elution with a mixture of 30% ethyl acetate in n-hexane and analyzed by gas chromatography-electron impact ionization mass spectrometry (GC-EI/MS) in the selected ion-monitoring mode (SIM) with permethrin as internal standard. Recovery was in the range 77–118% with relative standard deviations (RSD) between 2.5% and 10.2%. The limit of detection (LOD) was 6.5?µg/kg for cypermethrin. The developed method was linear in the injection range 6–30?ng, with correlation coefficients greater than 0.9957.     

Residue dynamics of chlorpyrifos and cypermethrin in/on pomegranate (Punica granatum L.) fruits and soil

Study on the residue dynamics of chlorpyrifos and cypermethrin in/on pomegranate (Punica granatum L.) and soil was carried out by conducting supervised field trials as per good agricultural practices. A modified QuEChERS was used to extract the insecticides in pomegranate peel and aril and soil. The limit of quantification (LOQ) of chlorpyrifos and cypermethrin were 0.01 and 0.05 mg kg^?1, respectively. Residues of the insecticides remained on the fruit surface and movement to the edible part (aril) was not observed. The residues after treatment on fruit peel were 2.46 and 3.51 mg kg^?1 and 2.84 and 4.54 mg kg^?1 for chlorpyrifos and cypermethrin, respectively, from recommended and double dose treatments. Chlorpyrifos residues degraded faster compared to cypermethrin. The pre-harvest intervals (PHIs) of chlorpyrifos were 22 and 35 days and those of cypermethrin 50 and 73 days, respectively, at recommended and double dose treatments. In the experimental field soil after the second application chlorpyrifos residues were 0.21 and 0.46 mg kg^?1 and cypermethrin residues 0.15 and 0.36 mg kg^?1. At harvest, both pesticides showed residues below the LOQ. Based on this study, application of cypermethrin towards harvest may be avoided whereas chlorpyrifos can be applied with 22 days PHI.