Trace Analysis of 2,4,5, TP and other Acidic Herbicides in Wheat Using Multicolumn-HPLC

Abstract

In continuation of our work dealing with multicolumn HPLC (MC-HPLC) techniques and their applicabilities for tracing a few compounds out of complex multicomponent matrices a residue analysis of the herbicides 2,4,5T and MCPA (phenoxyacids) in wheat is described. A simple plant extract with aqueous basic buffer is loaded in quantities of several 100μl onto a strong anion exchanger (column 1, C1) performing extraction of the acidic compounds, while the neutral and cationic substances are cluted thus attaiming on-column trace enrichment. Via mobile phase selection (pH change) elution from C1 is possible, the fraction (zone-cut) containing the compounds of interest is transferred onto C2 (reversed phase, RP2 an RP 18) on which peak compression is performed followed by (step)gradient elution. Detection limits in the lower ppb range are routinely obtained. A MC-HPLC chromatographic setup separation of eleven acidic herbicides in a formulation is also shown.     

固相微萃取-气相色谱-质谱联用测定水中的除草剂乙草胺

建立了固相微萃取技术与气相色谱-质谱联用快速检测水中除草剂乙草胺的方法。对萃取时间、搅拌速度及离子强度等实验条件进行了优化。该方法的线性范围为0．2—20μg／L；检出限为0．018μg／L；相对标准偏差为4．6％。该法可直接用于田间地面水中乙草胺的测定。     

Multiresidue analysis of atrazine, diuron and their degradation products in sewage sludge by liquid chromatography tandem mass spectrometry

A multiresidue method has been developed to analyze atrazine (ATZ), diuron (DIU), and their major degradation products, desethylatrazine (DEA), desisopropylatrazine (DIA), and dichlorophenylmethylurea in sewage sludge. Liquid chromatography coupled to electrospray tandem mass spectrometry (LC–ESI-MS–MS) allowed, in the multiple-reaction monitoring mode, the simultaneous analysis of these pesticides in only one run after their extraction with ethyl acetate–dichloromethane 90:10 (v/v) and a cleanup on a Florisil column. Stable isotopically labeled ATZ and DIU were used as internal standards to overcome matrix effects during the pesticide quantification. Using fortified samples, the method gave rise to 86–115% as mean recovery values depending on the analyte. Limits of detection (LODs) and of quantification (LOQs) ranging from 0.3 (DIA) to 1.5 (DEA) μg kg⁻¹ dw and from 0.4 (DIA) to 2.0 (DEA) μg kg⁻¹ dw, respectively, were sufficient to achieve the monitoring of these molecules in sludge from wastewater treatment plants of the Ile-de-France region.     

Trace analysis of sulfonylurea herbicides and their metabolites in water using a combination of off-line or on-line solid-phase extraction and liquid chromatography–tandem mass spectrometry

Two alternatives for the rapid simultaneous quantification of six sulfonylurea herbicides and five of their main degradation products in natural water are proposed. For concentration, the compounds were extracted on a polystyrene–divinylbenzene solid phase under pH and elution conditions that suppressed any hydrolysis. The eluates were analysed by liquid chromatography coupled to electrospray tandem mass spectrometry within 20 min. The whole method was validated and shown to give no hydrolysis artefacts. The application of off-line and on-line SPE of sulfonylureas enabled the 0.1 μg L⁻¹ and 1 ng L⁻¹ LOQ levels to be reached, respectively. The on-line SPE–LC–MS–MS method allowed the accurate quantitation of all sulfonylureas and three degradation products at 0.1 μg L⁻¹ or below in natural water, with an average repeatability of 8%.     

Nanoparticles in electrochemical sensors for environmental monitoring

We review the state-of-the-art application of nanoparticles (NPs) in electrochemical analysis of environmental pollutants. We summarize methods for preparing NPs and modifying electrode surfaces with NPs. We describe several examples of applications in environmental electrochemical sensors and performance in terms of sensitivity and selectivity for both metal and metal-oxide NPs. We present recent trends in the beneficial use of NPs in constructing electrochemical sensors for environmental monitoring and discuss future challenges.NPs have promising potential to increase competitiveness of electrochemical sensors in environmental monitoring, though research has focused mainly on development of methodology for fabricating new sensors, and the number of studies for optimizing the performance of sensors and the applicability to real samples is still limited.     

新一类2,3—二氰基吡嗪除草剂的合成及其活性研究

新一类２，３－二氰基吡嗪除草剂的合成及其活性研究向纪明ａ谢周ｂ英柏宁ｂ（ａ陕西安康师专化学系，陕西．安康，７２５０００；ｂ中山大学化学系，广州，５１０２７５关键词５－芳胺基－６－氯－２，３－二氰基吡嗪除草剂合成中图分类号Ｏ６２６．４１５５位取代的２，...     

新型除草剂双甲胺草磷(H-9201)在胡萝卜和土壤中的残留动态研究

建立了新型除草剂双甲胺草磷(H-9201)残留GC FPD检测方法,并对其在胡萝卜田的残留动态进行了研究.结果表明:植物样本的平均添加回收率为89.2%～101.8%,变异系数为:4.3%～5.0%,土壤中的平均添加回收率为90.8%～95.1%,变异系数为:3.0%～16.4%.本方法对双甲胺磷的检出限为:胡萝卜中为0.01 mg/kg,土壤中为0.005 mg/kg.残留动态研究表明:双甲胺草磷土壤中的半衰期为27.8 d,胡萝卜中的最终残留量＜0.02 mg/kg,土壤中的最终残留量＜0.4 mg/kg.     

Rapid determination of phenoxy acid residues in rice by modified QuEChERS extraction and liquid chromatography-tandem mass spectrometry

A new method for the analysis of phenoxy acid herbicide residues in rice, based on the use of liquid extraction/partition and dispersive solid phase extraction (dispersive-SPE) followed by ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS), is reported. 5% (v/v) formic acid in acetonitrile as the extraction solvent and inclusion of citrate buffer helped partitioning of all the analytes into the acetonitrile phase. The extract was then cleaned up by dispersive-SPE using C18 and alumina neutral as selective sorbents. Further optimization of sample preparation and determination allowed recoveries of between 45 and 104% for all 13 phenoxy acid herbicides with RSD values lower than 13.3% at 5.0 μg kg⁻¹ concentration level. Limit of detections (LODs) of 0.5 μg kg⁻¹ or below were attained for all 13 phenoxy acids. Quantitative analysis was done in the multiple-reaction monitoring (MRM) mode using two combinations of selected precursor ion and product ion transition for each compound. This developed method produced relatively higher recoveries of the acid herbicides with a smaller range of variation and less susceptibility to matrix effects, than the original QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method.     

Electrochemically modulated liquid chromatographic separation of triazines and the effect of pH on retention

Electrochemically modulated liquid chromatography (EMLC) manipulates analyte retention by changing the potential applied (E_app) to a conductive stationary phase. This paper applies EMLC to the separation of a set of seven triazines which are commonly used but environmentally hazardous herbicides. Experiments herein examine the influence of E_app and the pH of the mobile phase on triazine retention. The results are discussed in terms of: (1) retention of triazines of dissimilar acid strengths and by correlations with the pH of the mobile phase; (2) how changes in E_app and acid–base equilibria modulate elution; (3) qualitative insights into EMLC-based retention; and (4) potential merits of EMLC in realizing the rapid separation of the seven-component triazine mixture.     

Organosilane grafted acid-activated beidellite clay for the removal of non-ionic alachlor and anionic imazaquin

Clay adsorbents were prepared via two-step method to remove nonionic alachlor and anionic imazaquin herbicides from water. Firstly, layered beidellite clay, a member of smectite family, was treated with acid in hydrothermal process; secondly, common silane coupling agents, 3-chloro-propyl trimethoxysilane or triethoxy silane, were grafted on the acid treated samples to prepare adsorbent materials. The organically modified clay samples were characterized by powder X-ray diffraction, N₂ gas adsorption, and FTIR spectroscopy. It was found that the selective modification of clay samples displayed higher adsorption capacity for herbicides compared with acid activated clay. And the amount of adsorption is increased with increasing the grafting amount of silane groups. Clay grafted with 3-chloro-propyl trimethoxysilane is an excellent adsorbent for both alachlor and imazaquin but triethoxy (octyl) silane grafted clay is more efficient only for alachlor removal.