Simultaneous determination of cypermethrin and fenvalerate residues in tomato by gas chromatography and their applications to kinetic studies after field treatment

In this study simultaneous determination of cypermethrin and fenvalerate residues in tomato fruit (Lycopesicon esculentum) grown in Khartoum, Sudan, was carried out using gas chromatography with electron capture detector (GC‐ECD). The method was linear in the ranges of 0.075–0.009 and 0.75–0.037 mg/mL for cypermethrin and fenvalerate, respectively. The limits of detection and quantification were found to be 0.003 and 0.01 mg/mL and 0.014, 0. 047 mg/mL for cypermethrin and fenvalerate, respectively. The recoveries of cypermethrin and fenvalerate spiked in tomato were 97 ± 7.5 and 99.5 ± 1.8%, respectively. The kinetic study of the degradation of both pesticides was performed and the ultimate evaluation of the kinetic data revealed a first‐order kinetics with respect to the tomato fruit; an explanation was put forward to account for the results. Copyright © 2011 John Wiley & Sons, Ltd.     

硅胶管采样—液相色谱法测定空气中的氯氰菊酯

本文报道空气中氯氰菊酯的高效液相色谱测定方法，空气样品用硅胶管采样，经甲醇洗脱后用ＨｙｐｏｒｓｉｌＯＤＳ柱分离，紫外检测器检测，在本法的测定条件下，最低检测浓度为０．０４ｍｇ／ｍ＾３，当氯氰菊酯浓度范围为０～２５．０ｍｇ／Ｌ时，呈线性响应关系，相对标准偏差为２．４％～８．４％，本法的解吸效率为９６．８％～１００．３％，采样效率为１００％，氯氰菊酯在硅胶管中可稳定７ｄ。     

Efficient preparative separation of β‐cypermethrin stereoisomers by supercritical fluid chromatography with a two‐step combined strategy

An efficient two‐step method has been developed for the separation of β‐cypermethrin stereoisomers by supercritical fluid chromatography with polysaccharide chiral stationary phases. With respect to retention, selectivity, and resolution of β‐cypermethrin, the effects of chiral stationary phases, cosolvents, mobile phases, and column temperature have been studied in detail. Through a two‐step separation, β‐cypermethrin was firstly separated by using a cellulose‐derived chiral stationary phase to obtain two stereoisomeric pairs, and further resolved on an amylose‐based chiral stationary phase to produce four enantiopure stereoisomers. The electronic circular dichroism patterns of the first‐ and the third‐eluted isomers in methanol solution showed the mirror image of each other in the wavelength range 200∼300 nm, indicating that they were a pair of enantiomers. Moreover, the second‐ and the fourth‐eluted isomers were also enantiomers. This proposed two‐step strategy showed low solvent consumption, fast separation speed, and high‐purity, which may provide an effective approach for preparative separation of compounds with multiple chiral centers and difficult‐to‐separate multicomponent samples.     

Preparation and Characterization of Beta Cypermethrin Nanosuspensions by Diluting O/W Microemulsions

Nanosuspensions of beta cypermethrin with narrow size distribution were prepared from O/W microemulsions. Dynamic light scattering showed that the size of nanoparticles of beta cypermethrin changed little by increasing the volume of diluted water. Transmission electron microscopy confirmed that these nanoparticles have spherical shape. The normal phase high performance liquid chromatography assay showed that the precipitation had no influence on the composition of pesticide. The dissolubility of the pesticide shows that the formulation was approved controlled release.     

高效液相色谱二极管阵列检测器测定氯氰菊酯

本文采用高效液相色谱法和二极管阵列检测器，分离了农药氯氰菊酯的四个同分异构体，同时利用色谱保留值规律和光谱特征吸收曲线综合进行定性分析，记录了每个组分的峰上坡，峰顶和峰下坡三个不同部分在２２０－３２０ｎｍ波段的光谱叠合图并进行比较，以确定峰的纯度，并测定了异构体的顺反比例。     

Organotin wood preservatives: Their compatibility with synthetic pyrethroid insecticides

The stability of three synthetic pyrethroids (cypermethrin, deltamethrin and permethrin) to selected tributyltin compounds, Bu₃SnX [where X = OSnBu₃, Cl, O₂CC₆H₅, O₂C(naphthenyl), OSO₂C₂H₅], (Bu₃SnO)₃PO and (Bu₄N) (Bu₃SnCl₂), in toluene solution was investigated by infrared spectroscopy over a 24-week period. It was found that only (Bu₃Sn)₂O reacted with the pyrethroids and that their order of reactivity was cypermethrin>deltamethrin>permethrin. An attempt was made to elucidate the reaction mechanism(s) occurring between (Bu₃Sn)₂O and the pyrethroids by studying mixtures of this tributyltin fungicide with simple model compounds, R¹CO₂R² where R¹=CH₃; R²=CH₂C₆H₅ and R¹=cyclo-C₃H₅ and R²=CH₂C₆H₅.