QuEChERS and solid phase extraction methods for the determination of energy crop pesticides in soil,plant and runoff water matrices

QuEChERS and solid phase extraction (SPE) methods were applied for determining four herbicides (metazachlor, oxyfluorfen, quizalofop-p-ethyl, quinmerac) and one insecticide (α(±)-cypermethrin) in runoff water, soil, sunflower and oilseed rape plant matrices. Determination was performed using gas chromatography mass spectrometry (GC-MS), whereas high-pressure liquid chromatography mass spectrometry (HPLC-MS) was used for quinmerac. In all substrates linearity was evaluated using matrix-matched calibration samples at five concentration levels (50–1000 ng L^?1 for water, 5–500 μg kg^?1 for soil and 2.5–500 μg kg^?1 for sunflower or oilseed rape plant). Correlation coefficient was higher than 0.992 for all pesticides in all substrates. Acceptable mean recovery values were obtained for all pesticides in water (65.4–108.8%), soil (70.0–110.0%) and plant (66.1–118.6%), with intra- and inter-day RSD% below 20%. LODs were in the range of 0.250–26.6 ng L^?1 for water, 0.10–1.8 μg kg^?1 for soil and 0.15–2.0 μg kg^?1 for plants. The methods can be efficiently applied for field dissipation studies of the pesticides in energy crop cultivations.     

Determination of organochlorine pesticides in river water using dispersive liquid–liquid microextraction and gas chromatography–electron capture detection

Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD), has been developed for the extraction and determination of 14 organochlorine pesticides (hexachlorocyclohexanes (α-HCH, β-HCH and δ-HCH), Lindane (γ-HCH), Aldrin, Dieldrin, Endrin, Heptachlor, Heptachlor epoxide, α-Chlordane, β-Chlordane and p,p′-DDT, p,p′-DDD, p,p′-DDE) in river water samples. Factors relevant to the microextraction efficiency, such as the kind of extraction and disperser solvent, their volume and the salt effect was investigated and optimised. In this method the appropriate mixture of extraction solvent (13.5 µL carbon disulphide) and disperser solvent (0.50 mL acetone) were rapidly injected into the aqueous sample by syringe. The values of the detection limit of the method were in the range of 0.05–0.001 µg L^?1, while the relative standard deviations for five replicates varied from 2.7 to 9.3%. A good linearity (0.9894 ≤ r ² ≤ 0.9998) and a broad linear range (0.01–200 µg L^?1) were obtained. The method exhibited enrichment factors ranging from 647 to 923, at room temperature. The relative standard deviations varied from 2.7 to 9.3% (n = 5). The relative recoveries of each pesticide from water samples at spiking levels of 2.00 and 10.0 µg L^?1 were 88.0–111.0% and 95.8–104.1%, respectively. Finally, the proposed method was successfully utilised for the preconcentration and determination of the organochlorine pesticides in the Jajrood River water samples.     

Determination of 61 organic pollutants in drinking water by solid phase extraction followed by liquid and gas chromatography coupled to tandem mass spectrometry: an analytical strategy for a routine laboratory

A method for determination of 61 organic pollutants (polycyclic aromatic hydrocarbons and organochlorine, organophosphorous and organonitrogen pesticides) is proposed. It is based on solid phase extraction (SPE) and subsequent analysis of the extract by liquid and gas chromatography coupled to tandem mass spectrometry. Method validation yielded to the following values: limits of quantification, from 0.005 to 0.020?µg?L^?1; trueness, 95% to 113% and reproducibility (as percent relative standard deviation), 2% to 15%. Additionally, the method performed well in various proficiency tests.     

Low‐density extraction solvent based solvent‐terminated dispersive liquid–liquid microextraction for quantitative determination of ionizable pesticides in environmental waters

A rapid, efficient, and new solvent terminated dispersive liquid–liquid microextraction technique coupled with HPLC was developed for selective extraction and analysis of s‐triazine herbicides from environmental water samples. Important parameters influencing the extraction process including type and volume of extraction and disperser solvent, extraction time, sample pH, ionic strength, and extraction temperature were successfully optimized. Under the optimal conditions, there are excellent linear relationships between the analytical results and concentration in the range of 10–400 mg/L for atrazine, propazine, prometryn, and terbutryn. LOD and LOQ ranged from 0.60 to 2.33 μg/L and 2.0 to 7.7 μg/L, respectively. Performance of the analytical technique was evaluated by carrying out the repeatability and reproducibility analyses that were ranged from 2.86 to 5.66% and 4.64 to 5.89% for 100 μg/L of each target analyte, respectively. The proposed method has been successfully applied to the analysis of real water samples and acceptable relative recoveries over the range of 65.93–101.46%, with RSDs ≤ 8.80%, were obtained. The overall results have been compared with the literature values. Thus, the method developed could efficiently be used for selective extraction of the target analytes from complex matrices, particularly environmental waters.     

Graphene grafted silica‐coated Fe3O4 nanocomposite as absorbent for enrichment of carbamates from cucumbers and pears prior to HPLC

In this paper, a novel graphene (G) grafted silica‐coated Fe₃O₄ nanocomposite was fabricated by the chemical bonding of G onto the surface of silica‐coated Fe₃O₄ nanoparticles. Some carbamates (metolcarb, carbaryl, pirimicarb, and diethofencarb) in cucumber and pear samples were enriched by this nanocomposite prior to their determination by HPLC with UV detection. Experimental parameters that may affect the extraction efficiency were investigated. Under the optimum conditions, a linear response was achieved in the concentration range of 0.5–100.0 ng/g for metolcarb, carbaryl, and diethofencarb, and 1.0–100 ng/g for pirimicarb with the correlation coefficients (r) ranging from 0.9956 to 0.9984. The LOD (S/N = 3) of the method were found to be in the range from 0.08 to 0.2 ng/g. The RSDs were in the range from 2.4 to 5.8%. The results indicated that the G grafted silica‐coated Fe₃O₄ nanocomposite was stable and efficient for magnetic SPE and has a great application potential for the preconcentration of other organic pollutants from real samples.     

Potential of atmospheric pressure chemical ionization source in GC‐QTOF MS for pesticide residue analysis

The potential applications of a new atmospheric pressure source for GC‐MS analysis have been investigated in this work. A list of around 100 GC‐amenable pesticides, which includes organochlorine, organophosphorus and organonitrogenated compounds, has been used to evaluate their behavior in the new source. Favoring the major formation of the molecular ion in the source has been the main goal due to the wide‐scope screening possibilities that this fact brings in comparison with the traditional, highly fragmented electron ionization spectra. Thus, the addition of water as modifier has been tested as a way to promote the generation of protonated molecules. Pesticides investigated have been classified into six groups according to their ionization/fragmentation behavior. Four of them are characterized by the abundant formation of the protonated molecule in the atmospheric pressure source, mostly being the base peak of the spectrum. These results show that wide‐scope screening could be easily performed with this source by investigating the presence of the protonated molecule ion, MH+. The developed procedure has been applied to pesticide screening in different food samples (nectarine, orange and spinach) and it has allowed the presence of several pesticides to be confirmed such as chlorpyriphos ethyl, deltamethrin and endosulfan sulfate. The availability of a quadrupole time‐of‐flight instrument made it feasible to perform additional MS/MS experiments for both standards and samples to go further in the confirmation of the identity of the detected compounds. Results shown in this paper have been obtained using a prototype source which exhibits promising features that could be applied to other analytical problems apart from those illustrated in this work. Copyright © 2010 John Wiley & Sons, Ltd.     

A Photochemistry Technique Using Ultraviolet Irradiation Followed by Gas-Liquid Chromatography to Confirm the Identity of Some Organochlorine Pesticides

Abstract

A procedure involving ultraviolet (UV) irradiation followed by gas-liquid chromatographic (GLC) detection of photodecomposition products to confirm the identity of selected organochlorine pesticides is described. The Irradiation intensity was standardized by determining the position relative to the UV source which resulted in equal GLC peak heights for the parent compound and major photo-decomposition product after 8 minutes of exposure of a solution of heptachlor epoxide in isooctane. Chromatograms showing photo-decomposition patterns for 33 compounds are presented. Observations and comments on the applicability of this technique to organo-chlorine pesticide residue confirmation are reported.     

Fe3O4纳米粒子修饰多壁碳纳米管的制备及在水和蜂蜜样品中痕量菊酯类农药分析中的应用

通过化学共沉淀法使Fe₃O₄纳米粒子负载于酸化多壁碳纳米管(AMWNTs)表面,得到Fe₃O₄/AMWNTs磁性纳米材料。该材料具有很好的磁响应度和分散性,将其用于富集痕量拟除虫菊酯类农药残留,结果证明该复合材料对菊酯类农药的吸附性能良好。通过对影响萃取性能的几种因素如离子强度、萃取时间和解吸时间依次进行优化,在最优条件下,建立了Fe₃O₄/AMWNTs磁性分散固相萃取-气相色谱测定6种菊酯类农药残留的分析方法。线性范围在0.5~50 μg/L之间,相关系数(R²)大于0.990,检出限为0.07~0.20 μg/L,精密度为3.8%~8.1%。该方法用于河水、鱼塘水和两种市售蜂蜜中菊酯类农药的残留分析,回收率高于78.4%。该方法操作简便、灵敏度高,能够满足环境水样及蜂蜜样品中痕量菊酯农药残留的分析需求。     

杨石先对农药化学学科的重要贡献及其学术思想

杨石先先生一生献身于我国的教育事业与化学学科的发展,在62年中为我国培养了无数高质量的科教人才。他除了长期担任南开大学校长之外, 还创建了我国大学第一个专职研究所,即元素有机化学研究所。他率先开展了我国元素有机化学与农药化学的科学研究,领导了元素有机化学国家重点实验室的建立,是我国元素有机化学和农药化学的奠基人和开拓者。他倡导用有机化学的专业知识,科学和系统地开展农药化学研究,组建队伍获得20项科研成果,发表上百篇科学与论述性论文,为我国开展自主创新农药研究事业作出重要贡献。在农药化学学科的学术思想中,他强调要弄清该学科的交叉性、系统性和内在规律性,倡导要学习国际先进经验,要结合国情自主创新,要为国家经济服务,要对世界农药科技做出贡献。他毕生对人才培养给予了特别的重视,为我国科技事业持续发展作出了重大贡献。     

有机磷类农药残留检测技术的应用

作为一类高效、广谱的杀虫剂,有机磷类农药被广泛用于农作物病虫防治领域,但它产生的危害也不容忽视。论述了近年来国内外有机磷类农药检测技术的应用,比较各种方法的优缺点,为农药残留检测的应用提供了参考。