间二甲苯氨氧化法制备间苯二腈催化剂研究

对氨氧化法制备间苯二腈催化剂进行了研究. 在“微反-色谱”联用装置上完成催化剂的评比和筛选后,在内径30 m m 的石英管固定床反应器上印证并进行工艺条件实验. 考察了反应温度、氨比、空气比和空速对反应的转化率,摩尔收率和选择性的影响. 在所确定的工艺条件下使用m -509 号催化剂,转化率高达99.8% 、摩尔收率70.4% ,生成的间苯二腈为白色针状结晶,纯度高于98.5% . 在湖南南天实业股份有限公司的560 m m 工业流化床反应塔上进行了为期6 个月的工业性试验,摩尔收率达66.5% ,间苯二腈含量高于98% ,单腈含量低于0.25% ,性能优于现行工业催化剂.     

Screening Method for the Determination at Parts Per Trillion Levels of Pesticide Residues in Vegetables Combining Solid‐Phase Microextraction and Gas Chromatography‐Tandem Mass Spectrometry

Abstract

A new analytical method is proposed for determining residues of 70 pesticides of different chemical families at parts per trillion levels in fresh vegetables. For that, only 4 g of the vegetable samples were quickly extracted with 10 ml of ethyl acetate. The method is based on a vanguard/rearguard strategy that reduces the average time required per sample when the method is applied to a high number of vegetable samples in a quality control laboratory. At the beginning, an aliquot of the extract is evaporated and re‐dissolved in a mixture water:acetone (9∶1 v/v). For screening purposes, the pesticides were extracted for only 10 min by direct immersion of a solid‐phase microextraction (SPME) fiber (65 µm polydimethylsiloxane‐divinylbenzene, PDMS‐DVB). The SPME device was automated and on‐line coupled to a gas chromatograph with an ion trap mass spectrometer (GC‐MS) operated in full scan mode for screening in less than 18 min those samples that potentially contain pesticides above 0.01 mg kg^?1 (cut off value). After that, only those potentially non‐negative samples were reanalyzed by a sensitive quantifying/confirming method that re‐extract by SPME the pesticides in 55 min of absorption and determine them by GC with tandem MS (MS/MS). The method has been validated following EU guidelines and compared with a conventional extraction method based on the use of higher amounts of organic solvents. The limits of detection (LOD), confirmation (LOC) and quantitation (LOQ) as well as the calibration curves obtained allowed the determination of the target pesticides at concentrations clearly below the maximum residue levels (MRL) stated by EU being possible the determination of parts per trillion of the pesticides in ecological (green) vegetables. The method has been applied to the analysis of real samples and the results compared with those obtained by a conventional extraction method accredited by ENAC (Spanish Accreditation Body). The proposed method was also evaluated participating in a proficiency test with adequate results (z‐score among±2).     

Determination of nicotinyl pesticide residues in vegetables by micellar electrokinetic capillary chromatography with quantum dot indirect laser-induced fluorescence

A new assay was developed by use of micellar electrokinetic capillary chromatography with indirect LIF fluorescence for the determination of thiamethoxam, acetamiprid, and imidacloprid residues in vegetables, in which the cadmium telluride quantum dots (QDs) synthesized in aqueous phase were used as fluorescent background substance and their excitation and emission wavelengths matched with LIF detector by engineering their size. The factors that affected the peak height and the resolution were optimized. The running buffer was composed of 4.4 μM cadmium telluride QDs as fluorescent background substance, 40 mM borate and 60 mM SDS, and its pH was adjusted to 8.0. The separation voltage was 25 kV. Under the optimum conditions, the detection limits were 0.05, 0.01, and 0.009 mg/kg; the linear dynamic ranges were 0.5-30, 0.1-30, and 0.1-30 mg/L; and the average recoveries of spiked samples were 72.0-101.2, 74.0-106.7, and 77.8-105.1% for thiamethoxam, acetamiprid, and imidacloprid, respectively. The assay can meet the requirement of maximum residue limits to these three pesticides in the regulations of European Union and Japan, and has been applied for determining their residues in vegetables.     

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues

Unintended pesticide pollution in soil, crops, and adjacent environments has caused several issues for both pesticide users and consumers. For users, pesticides utilized should provide higher yield and lower persistence while considering both the environment and agricultural products. Most people are concerned that agricultural products expose humans to pesticides accumulating in vegetation. Thus, many countries have guidelines for assessing and managing pesticide pollution, for farming in diverse environments, as all life forms in soil are untargeted to these pesticides. The stable isotope approach has been a useful technique to find the source of organic matter in studies relating to aquatic ecology and environmental sciences since the 1980s. In this study, we discuss commonly used analytical methods using liquid and gas chromatography coupled with isotopic ratio mass spectrometry, as well as the advanced compound-specific isotope analysis (CSIA). CSIA applications are discussed for tracing organic pollutants and understanding chemical reactions (mechanisms) in natural environments. It shows great applicability for the issues on unintended pesticide pollution in several environments with the progress history of isotope application in agricultural and environmental studies. We also suggest future study directions based on the forensic applications of stable isotope analysis to trace pesticides in the environment and crops.     

固相萃取-毛细管气相色谱法测定人参制品中19种有机氯农药的残留量

毛细管气相色谱法;有机氯农药;固相萃取;人参制品     

Biodegradation and bioaccumulation of fenitrothion in rat liver

The biodegradation of fenitrothion O,O-dimethyl-O-(3-methyl-4-nitro phenyl) phosphorothioate was investigated in rat liver after administration of various doses (5 mg/100 g body weight and 20 mg/100 g body weight) in acute treatment and 1 mg/100 g body weight in chronic treatment. High performance liquid chromatography of the pesticide and its metabolites formed in liver in acute treatment showed time-dependent sequential conversion of pesticide into three major metabolites within 24 h. These metabolites were separated and purified to homogenity by HPLC and characterized by IR spectroscopy as O,O-dimethyl-O-(3-methyl-4-amino phenyl) phsophorothioate (metabolite 1), O,O-dimethyl phosphorothioate (metabolite II) and O,O-dimethyl phosphate (metabolite III) in the fi rst dose (5 mg/100 g body weight). Metabolite II was found to be different in the second dose (20 mg/100 g body weight) and identified as O,O-dimethyl O-3-methyl-4-amino phenyl phosphate. The results with the fi rst dose indicated reduction of the nitro group in fenitrothion as step I followed by hydrolytic clevage of the P-O-aryl bond in metabolite I and oxidative desulphurylation of metabolite II. At higher dose (20 mg/100 g body weight) oxidative desulphurylation takes place as step II followed by hydrolysis of metabolite II. The bioaccumulation of fenitrothion within 60 days during chronic treatment showed no metabolite but continuous reduction in fenitrothion concentration, indicating excretion of pesticide and its products in urine and in faeces.     

液相色谱-串联质谱法同时测定三七中508种农药残留

采用液相色谱-串联质谱(LC-MS/MS)建立了可在20 min内快速测定三七中508种农药残留的方法。样品经改良的QuEChERS方法提取,分散固相萃取法(d-SPE)净化后,在多反应监测(MRM)模式下进行LC-MS/MS分析,内标法定量。在优化实验条件下,508种农药均在0.005～0.4 mg/L范围内线性关系良好,方法检出限(LOD)为0.005～0.1 mg/kg;在100μg/kg加标水平下,除8种农药外,其余500种农药的回收率均在50.2%～117%之间,且相对标准偏差(RSD)均不大于15%;其中有468种农药的回收率为70%～120%。该方法样品前处理简单快速,灵敏度、准确度和精密度均符合农药多残留检测技术的要求,适用于三七中508种农药残留的快速筛查。     

Determination of Organophosphorus Pesticides in Water Using C18 or Florisil Sep-Pak Cartridge and Gas Chromatography with Flame-Photometric Detection

Simple methods for the concentration and clean-up of fifteen organophosphorus pesticides in water using a C₁₈ Sep-Pak cartridge or a Florisil Sep-Pak cartridge and subsequently determining the pesticides by gas chromatography with flame photometric detection have been developed. The conditions for stepwise or simultaneous desorption of these pesticides from the Sep-Pak cartridges are given.     

快速气相色谱法测定蔬菜中甲胺磷和水胺硫磷残留量

蔬菜中甲胺磷和水胺磷残余经氯仿萃取后，用气相色谱－火焰光度检测器（ＧＣ－ＦＰＤ）直接测定，色谱柱为ＤＢ－１７大口径石英毛细管柱，采用气相色谱－离子阱质谱系统检测样品中的甲胺磷和水胺硫磷，在三个不同含量水平的收率试验中，本法的回收率为９３．６％－１０４．１％，最低检测限可达０．０６μｇ／ｇ