Analysis of Herbicide Krovar I™ by Liquid Chromatography with Atmospheric Pressure Chemical Ionization Mass Spectrometry

Abstract

A simple, very efficient method is presented for routine analysis of herbicide Krovar I? (active components bromacil and diuron) in water and soil samples. Water samples were extracted by liquid–liquid extraction with dichloromethane (DCM) as extraction solvent. For soil samples two different extraction techniques were compared: microwave-assisted solvent extraction and a shaking technique using a platform shaker. Extracts were analyzed by high performance liquid chromatography using a water:methanol gradient. Liquid chromatography was coupled with atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) for quantification of bromacil and diuron. Optimization of the APCI-MS was done by using standards in the flow injection analysis mode (FIA). Method detection limit for liquid samples for bromacil is 0.04 µg L^?1 and for diuron 0.03 µg L^?1. Method detection limit for soil samples is 0.01 µg g^?1 dry weight for both compounds. Results of analysis of field samples of water and soil are also presented.     

Applicability of microwave-assisted extraction combined with LC-MS/MS in the evaluation of booster biocide levels in harbour sediments

A new sample treatment method for the determination of four common booster biocides (Diuron, TCMTB, Irgarol 1051 and Dichlofluanid) in harbour sediment samples has been developed that uses liquid chromatography-tandem mass spectrometry (LC-MS/MS) after microwave-assisted extraction, followed by clean-up and a solid phase extraction preconcentration step (MAE-SPE). The effects of different variables on MAE-SPE were studied. The recoveries obtained were greater than 75%, and the relative standard deviation was less than 7%. The detection limits ranged between 0.1 and 0.3 ng g⁻¹. The developed methodology was successfully applied to the evaluation of the presence of booster biocides in sediment samples from different harbours and marinas of Gran Canaria Island (Canary Islands, Spain).     

Heterogeneous photocatalytic degradation of diuron on zinc oxide: Influence of surface-dependent adsorption on kinetics, degradation pathway, and toxicity of intermediates

Heterogeneous photocatalytic reaction has been generally applied for degradation of toxic contaminants. Degradations of a compound using the same kind of catalyst that was synthesized differently are commonly found in literature. However, the reported degradation intermediates are normally inconsistent. This issue is especially important for the degradation of toxic compounds because intermediates may be more toxic than their parent compounds and understanding the reason is necessary if appropriate catalysts are to be designed. This work systematically compares the photocatalytic degradation of diuron, a toxic recalcitrant herbicide, on two forms of zinc oxide (ZnO), i.e., conventional particles with zinc- and oxygen-terminated polar surfaces as the dominating planes, and nanorods with mixed-terminated nonpolar surfaces. Experimental and theoretical results indicate that both the rate of reaction and the degradation pathway depend on the adsorption configuration of diuron onto the surface. Diuron molecules adsorb in different alignments on the two surfaces, contributing to the formation of different degradation intermediates. Both the aliphatic and aromatic sides of diuron adsorb on the polar surfaces simultaneously, leading to an attack by hydroxyl radicals from both ends. On the other hand, on the mixed-terminated surface, only the aliphatic part adsorbs and is degraded. The exposed surface is therefore the key factor controlling the degradation pathway. For diuron degradation on ZnO, a catalyst confined to mixed-terminated surfaces, i.e., ZnO nanorods, is more desirable, as it avoids the formation of intermediates with potent phytotoxicity and cytogenotoxicity.     

Effects of sewage sludge amendments on pesticide sorption and leaching through undisturbed Mediterranean soils

The Gharb region in Morocco is an important agricultural zone where soils receive pesticide treatments and organic amendments to increase yields. The groundwater aquifer in the Gharb region is relatively shallow and thus vulnerable. The objective of this work was to study the influence of organic amendments on diuron, cyhalofop-butyl and procymidone leaching through undisturbed soil columns. Two soils were sampled from the Gharb region, a Dehs (sandy soil) and a R’mel (loamy clay soil). Following elution (124.5 mm), the amount of pesticide residues in the leachates of the sandy soil (0.06–0.21 %) was lower than in those of the loamy clay soil (0.20–0.36 %), which was probably due to preferential flow through the loamy clay soil. The amount of procymidone leached through the amended soil columns was greater than the control for the sandy soil only. The organic amendments did not significantly influence diuron and cyhalofop-butyl leaching in either of the soils. The application of organic amendments affected the amounts of dissolved organic matter (DOM) eluted and thus pesticide leaching as a function of soil-type. Nevertheless, in some case, the formation of pesticide-DOM complexes appeared to promote pesticide leaching, thus increasing groundwater contamination risks.     

Adsorption kinetics and isotherms of pesticides onto activated carbon-cloth

Adsorption of pesticides ametryn, aldicarb, dinoseb and diuron from aqueous solution onto high specific area activated carbon-cloth was studied. Kinetics of adsorption was followed by in situ UV-spectroscopy and the data were treated according to various rate models. The extent of adsorption was determined at the end of 125 min adsorption period. Rate constants and the extent of adsorption for the four pesticides were found to follow the order: dinoseb > ametryn > diuron > aldicarb. Adsorption isotherms were derived at 25 °C on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundlich models. The fits of experimental data to these equations were examined. The types of interactions between the surface and pesticide molecules were discussed.     

Effects of low concentrations of the phenylurea herbicide diuron on biofilm algae and bacteria

A system of recirculating channels was used in this study to examine the long-term effects (29 d) of environmentally realistic concentrations of the herbicide diuron (from 0.07 to 7 μg L⁻¹) on biofilm communities. The autotrophic activity of biofilms was affected by this herbicide, as reflected by a marked decrease in the photosynthetic efficiency. Diuron exposure also increased chlorophyll-a content and reduced the biovolume of diatom taxa at low concentrations. The effects on bacteria were also remarkable. Bacterial abundance was reduced after a week of exposure to the herbicide at a range of concentrations. Effects were on the number of live bacteria and on the increase in the leucine-aminopeptidase activity. It is suggested that inputs of herbicides to the river ecosystem at low concentrations may cause a chain of effects in the biofilm, which include inhibitory effects on algae but also indirect effects on the relationships between biofilm components.     

Environmental impact of diuron transformation: a review

Diuron is a biologically active pollutant present in soil, water and sediments. A synthesis of literature data on its physicochemical properties, partitioning behaviour, abiotic and biotic transformations, toxicological and ecotoxicological impacts has been here performed. Data have shown that diuron is generally persistent in soil, water and groundwater. It is also slightly toxic to mammals and birds as well as moderately toxic to aquatic invertebrates. However, its principal product of biodegradation, 3,4-dichloroaniline exhibits a higher toxicity and is also persistent in soil, water and groundwater. Thus, diuron indirectly possesses a significant amount of toxicity and could be a potential poisoning pesticide contaminant of groundwater. Unfortunately, groundwater contamination will still persist despite the progressive suppression of diuron (Directive 200/60/CE). Therefore, determining the main factors influencing its degradation and its ecotoxicological effects on the environment and health could provide a basis for further development of bioremediation processes.     

Immunotoxicity in ascidians: Antifouling compounds alternative to organotins – II. The case of Diuron and TCMS pyridine

Using short-term hemocyte cultures of the colonial ascidian Botryllus schlosseri exposed to various sublethal concentrations of Diuron (3-(3,4-diclorophenyl)-1,1-dimethylurea) and TCMS pyridine (2,3,5,6-tetrachloro-4-(metylsulphonyl)pyridine), we evaluated their immunotoxic effects through a series of cytochemical assays previously used for organotin compounds. At concentrations higher than 250 μ M and 10 μ M for Diuron and TCMS pyridine, respectively, both biocides exerted immunosuppressant effects on Botryllus hemocytes, causing i) deep changes in the cytoskeleton that irreversibly affect cell morphology and phagocytosis, ii) induction of DNA damage, iii) leakage of oxidative and hydrolytic enzymes due to membrane alteration. Unlike organotin compounds, Diuron and TCMS pyridine do not inhibit cytochrome-c-oxidase, and only TCMS pyridine triggers oxidative stress. When co-present, they exert an antagonistic interaction on cytoskeletal components.     

柠檬酸-Fe（Ⅱ）／K2S2O8降解泥水体系中敌草隆的研究

研究了泥水体系中柠檬酸-Fe（Ⅱ）／K2SO8降解敌草隆时各影响因子的作用机制,通过正交实验确定了反应的最佳操作条件为：K2SO8浓度为2．0mmol／L,Fe（Ⅱ）浓度为1．0mmol／L,柠檬酸浓度为0．5mmol／L,反应时间为120min,pH=7．0。此奈件下,0．1mmol／L敌草隆降解率可达97．6％。采用分子探针竞争实验鉴定了体系中产生的硫酸根自由基。     

水体系中Fe(Ⅱ)/K2S2O8降解敌草隆的研究

在初始pH 7.0的Fe(Ⅱ)/K2S2O8体系中,分别研究了K2S2O8和Fe(Ⅱ)初始浓度以及Fe(Ⅱ)分批加入对敌草隆降解的影响,结果表明,在pH 7.0,K2S2O8和Fe(Ⅱ)初始浓度分别为2.0mmol·l-1和1.0mmol·l-1时,反应300min后,0.1mmol·l-1敌草隆的降解率达到40.0%,Fe(Ⅱ)分批加入能够促进敌草隆的降解.另外,通过对Fe(Ⅱ)/K2S2O8,EDTA-Fe(Ⅱ)/K2S2O8,柠檬酸-Fe(Ⅱ)/K2S2O8以及K2S2O3-Fe(Ⅱ)/K2S2O8四种Fe(Ⅱ)/K2S2O8体系的对比研究,发现在Fe(Ⅱ)/K2S2O8体系中,加入Fe(Ⅱ)的螯合剂EDTA和柠檬酸以及还原剂K2S2O3能够明显促进敌草隆降解.采用分子探针法的竞争实验鉴定了体系中产生的硫酸根自由基.