超临界流体萃取气相色谱法测定粮谷中拟除虫菊酯残留量

本文建立了一种离线超临界流体萃取、气相色谱法快速测定粮谷（大米、小米、玉米）中的二氯苯醚菊酯、氯氰菊酯、速灭杀丁、溴氰菊酯等４种拟除虫菊酯残留量的方法。在优化条件下，菊酯被提取并收集于正己烷中，定容后直接进行气相色谱测定。整个分析时间小于１ｈ。     

固相萃取-超高效液相色谱-三重四极杆质谱联用同时测定水中菊酯类农药多残留

应用固相萃取-超高效液相色谱-三重四极杆质谱(UPLC-MS/MS)联用技术,建立了水中20种菊酯类农药多残留的分析方法。通过对固相萃取柱、淋洗液、流动相等条件的优化,确定以Oasis HLB为固相萃取柱、正己烷-丙酮(9∶1,V/V)为淋洗液、0.1%乙酸水溶液-乙腈(7∶3,V/V)为流动相做水样预处理。在最优实验条件下,目标物的回收率为73.4%~124.5%,相对标准偏差(RSD)在5.7%~9.1%之间,线性范围均在1~2 000μg/L,各目标物标准品在UPLC-MS/MS系统中有效的线性相关(R2)为0.999以上。该方法具有检测限低、回收率高等优点,经实际样品测试,可适用于水中20种菊酯类农药多残留的同时检测。     

β‐Cyclodextrin polymer@Fe3O4 based magnetic solid‐phase extraction coupled with HPLC for the determination of benzoylurea insecticides from honey,tomato, and environmental water samples

In this work, a magnetic β‐cyclodextrin polymer was successfully prepared and used as an adsorbent for the magnetic solid‐phase extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, flufenoxuron, and chlorfluazuron) from honey, tomato, and environmental water samples. The influence of the main experimental conditions on the extraction was studied. Under the optimized conditions, the β‐cyclodextrin polymer@Fe₃O₄ showed an excellent extraction performance for the benzoylurea insecticides. A good linearity was obtained for the analytes in the range of 3.0–800 ng/g for honey samples, 0.3–160 ng/g for tomato samples, and 0.1–80.0 ng/mL for water samples, with the correlation coefficients above 0.9998. Satisfactory repeatabilities were achieved, with the relative standard deviations less than 5.7%. The limits of detection (S/N = 3) of the method for the benzoylurea insecticides were 0.2–0.8 ng/g for honey samples, 0.04–0.10 ng/g for tomato samples, and 0.02–0.05 ng /mL for water samples. The method was successfully used for the determination of the six benzoylurea insecticides residues in honey, tomato, and environmental water samples with a satisfactory result.     

The Design,Synthesis, and Evaluation of 1,5,7‐Trisubstituted‐3‐Pyridyl‐Xanthones for Use as Insecticides Starting from Pyripyropene A

A readily accessible template of 1,5,7‐trisubstituted‐3‐pyridyl‐xanthones was designed starting from naturally occurring pyripyropene A for agrichemical development. Our originally developed Ag₂CO₃‐mediated oxidative cyclization enabled ready access to the key scaffold, 1,5,7‐trihydroxy‐3‐chloro‐xanthone. The chemo‐ and regioselective sequential introduction of four substituents to the scaffold rapidly afforded the desired, structurally diverse 1,5,7‐trisubstituted‐3‐pyridyl‐xanthones. An evaluation of insecticidal activity revealed that one of the synthesized compounds retained insecticidal activity against vetch aphid and green peach aphid. The observed insecticidal spectrum was similar to that of pyripyropene A. The developed template could be a valuable aid for future agrichemical development.     

Headspace single-drop microextraction and GC–ECD determination of chlorpyrifos-ethyl in rat liver

The present work describes a headspace single-drop microextraction (HS-SDME) method in conjunction with gas chromatography electron capture detection (GC–ECD) for the determination of an organophosphate insecticide, chlorpyrifos-ethyl (CPF), in rat liver. Sample preparation included tissue homogenization with methanol in the presence of anhydrous sodium sulfate in order to isolate CPF from the matrix, followed by dilution with 10 mL of 0.1 M H₂SO₄ and headspace microextraction to a 2-μL drop of 1-octanol. The main factors affecting extraction efficiency were optimized [temperature 90 °C, preheating and extraction times of eight and six minutes, respectively, 2 g of (NH₄)₂SO₄, stirring rate of 1000 rpm, 200 μL of methanolic extract]. The method allows for the separation and quantitation of residue levels of CPF in the livers of rats exposed orally to that insecticide. Using internal standardization (with chlorpyrifos-methyl used as an internal standard), the linearity of the method was demonstrated in the range 10–2500 ng g⁻¹ with a correlation coefficient R > 0.996 and a satisfactory level of precision (RSD 3.85%, n = 6). Moreover, the results obtained with the new method do not differ from those obtained with the conventional residue method used in our laboratory. The feasibility of this HS-SDME approach as an equivalent analytical method for the determination of CPF in rat liver that possessess advantages such as low cost, low solvent consumption and high throughput was confirmed. Figure Headspace single-drop microextraction     

Determination of trace levels of pyrethroid metabolites in human urine by capillary gas chromatography-high resolution mass spectrometry with negative chemical ionization

Summary Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples and exhaustive solvent extraction, a carbodiimide-coupled esterification of the free carboxylic acids with hexafluoroisopropanol (HFIP) is applied. Identification of the derivatives formed is achieved by low-resolution electron-impact mass spectrometry (EIMS) using an ion-trap detector. Quantitation was by capillary gas chromatography—high-resolution mass spectrometry using negative chemical ionization (GC-NCIMS). 2-Phenoxybenzoic acid (2-PBA) served as internal standard. The limits of detection forcis- andtrans-DCCA,cis-DBCA, FPBA and 3-PBA were 0.03 μg L⁻¹ or below. The applicability of the presented method was tested on urine samples of persons exposed to low levels of pyrethroids.     

Nanoemulsified Formulation of Cedrela odorata Essential Oil and Its Larvicidal Effect against Spodoptera frugiperda (J.E. Smith)

Cedrela odorata L. is a plant species from the Meliaceae family that is cultivated for timber production. Although the C. odorata essential oil (EO) contains mainly sesquiterpenes, its insecticidal potential is unknown. The lipophilic properties and high degradation capacity of EOs have limited their application for use in pest control. However, the currently available knowledge on the nanoemulsification of EOs, in addition to the possibility of improving their dispersion, would allow them to prolong their permanence in the field. The objective of the present work was to develop a nanoemulsion of the C. odorata EO and to evaluate its larvicidal activity against Spodoptera frugiperda. The EO was obtained by the hydrodistillation of C. odorata dehydrated leaves, and the nanoemulsion was prepared with non-ionic surfactants (Tween 80 and Span 80) using a combined method of agitation and dispersion with ultrasound. The stability of the nanoemulsion with a droplet diameter of <200 nm was verified in samples stored at 5 °C and 25 °C for 90 days. Both the C. odorata EO and its corresponding nanoemulsion presented lethal properties against S. frugiperda. The results obtained provide guidelines for the use of wood waste to produce sustainable and effective insecticides in the fight against S. frugiperda. In addition, considering that a phytochemical complex mixture allows the simultaneous activation of different action mechanisms, the development of resistance in insects is slower.