Trace analysis of triazines and organophosphorus pesticides in water

A method for the determination of trace levels of triazines and organophosphorus pesticides in water is presented. The extraction method is based on a solid-phase extraction on C-18 bound silica SPE cartridges. A precolumn filled with Merck C-18 bound silica and home-made C-18 bound silica have been tested at a flow-rate of 3 ml/min with comparable preconcentration yields. A SIM-MS method using a (15)N labelled internal standard has been developed for the organophosphorus pesticides. Detection limits lower than 1 microg/L have been obtained. Separations have been carried out on a conventional GC column OV 17 (1 m) and a capillary column OV 17 (25 m) with a temperature program from 150 degrees C (2 min) to 300 degrees C (rate of 6 degrees C/min).     

Trace analysis of triazines and organophosphorus pesticides in water

A method for the determination of trace levels of triazines and organophosphorus pesticides in water is presented. The extraction method is based on a solid-phase extraction on C-18 bound silica SPE cartridges. A precolumn filled with Merck C-18 bound silica and home-made C-18 bound silica have been tested at a flow-rate of 3 ml/min with comparable preconcentration yields. A SIM-MS method using a ¹⁵N labelled internal standard has been developed for the organophosphorus pesticides. Detection limits lower than 1 g/L have been obtained. Separations have been carried out on a conventional GC column OV 17 (1 m) and a capillary column OV 17 (25 m) with a temperature program from 150° C (2 min) to 300° C (rate of 6° C/min).     

A cellulose column cleanup for organophosphorus pesticides

A simple, rapid method to clean up toxicological samples has been developed. The method greatly improves the matrix contribution to TLC or GLC analysis.     

C18 reversed-phase trace enrichment of organophosphorus pesticides and residues in water

Summary The efficiency of accumulation of traces of dialkylphosphates, dialkylphosphorothioates and dialkylphosphorodithioates and at the same time of the parent organophosphorus pesticides, from aqueous solutions, was investigated by reversed-phase adsorption with octadecyl-modified silica gel (Sep-Pak C₁₈ cartridge). For desorption, methanol was used as the most appropriate solvent for the subsequent methylation of dialkylphosphorus anions and for gas chromatographic analysis. The recoveries of dimethyl-and diethylphosphorothioates and-phosphorodithioates, both free and as ionassociation complexes with the tetraphenylarsonium cation, from water samples adjusted to pH 1.25 and 4 respectively, were comparable. The recovery of diethylphosphate was tripled by acidification of the water sample, whereas the accumulation of dimethylphosphate was unsuccessful. Although the anions were not quantitatively trapped on the cartridge, a detection limit of 1g/l for dialkyl-phosphorothioates and-phosphorodithioates was obtained with 10–20 ml sample volumes. The sample volume should not exceed 20 ml because of significant breakthrough of dialkylphosphorus anions on the C₁₈ cartridge with larger volumes. Under the optimum conditions for accumulation of organophosphorus residues the adsorption of organophosphorus pesticides is nearly quantitative with a detection limit 1–2 orders of magnitude higher than that for the residues. To enhance the detection limit to 1g/l the sample volume had to be increased to 100 ml, but there was then no possibility of achieving efficient simultaneous accumulation of the corresponding dialkylphosphorus anions. The procedure provides simple and rapid trace enrichment of organophosphorus pesticides and residues, in the control of surface waters polluted with these compounds, and is applicable in the field.

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C₁₈-Reversed-phase-Spurenanreicherung phosphororganischer Pestizide und Residuen in Wasser

Zusammenfassung Die Spurenanreicherung von Dialkylphosphaten, Dialkylthiophosphaten und Dialkyldithiophosphaten gleichzeitig mit ursprünglichen phosphororganischen Pestiziden aus wäßrigen Lösungen durch Reversed-phase-Adsorption an oktadecyl-modifiziertem Kieselgel (Sep-Pak-C₁₈-Patrone) wurde untersucht. Zur Desorption wurde Methanol als das geeignetste Lösungsmittel sowohl für die anschließende Methylierung der Dialkylphosphatanionen als auch für die gaschromatographische Analyse verwendet.Die Wiederauffindungsraten der freien bzw. mit Tetraphenylarsoniumkation ionenassoziierten Dimethyl-und Diethylthiophosphate und-dithiophosphate aus Wasserproben bei pH 1,25 bzw. 4 waren vergleichbar. Die Wiederauffindungsrate des Diethylphosphats wurde durch Ansäuern der Wasserprobe dreifach erhöht, während die Anreicherung des Dimethylphosphats in beiden Fällen erfolglos war. Obwohl die Anionen an der Patrone nicht quantitativ zurückgehalten wurden, wurde durch Behandlung der Wasserprobe von 10–20 ml eine Nachweisgrenze von 1g/l erhalten. In Anbetracht eines bedeutenden Durchbruchs der Dialkylphosphatanionen in der C₁₈-Patrone darf das Volumen der Wasserprobe den Wert von 20 ml nicht überschreiten.Unter den für die Anreicherung der phosphororganischen Residuen optimalen Bedingungen wurden phosphororganische Pestizide annähernd quantitativ adsorbiert, mit einer um 1–2 Größenordnungen höheren Nachweisgrenze. Damit diese den Wert von 1g/l erreicht, soll das Probevolumen auf 100 ml erhöht werden, ohne daß jedoch auf eine gleichzeitige wirksame Anreicherung der entsprechenden Dialkylphosphatanionen Anspruch erhoben wird.Das Verfahren ermöglicht eine einfache und schnelle Spurenanreicherung bei der an Ort und Stelle durchzuführenden Kontrolle der durch phosphororganische Pestizide und Residuen verunreinigten Oberflächengewässer.

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Presented at the Fifth European Conference on Analytical Chemistry EUROANALYSIS V, Cracow, August 26–31, 1984.     

Analytical methodology for organophosphorus pesticides used in Canada

An overview of analytical methodology for the determination of organophosphate pesticides residues in foods is presented. Sample extraction is carried out with acetone followed by a dichloromethane-hexane partition. The organic extract is purified by automated gel permeation chromatography and analysed by capillary gas chromatography with flame photometric or thermionic detection. Confirmation can be carried out by a variety of chemical derivatization techniques including hydrolysis followed by reaction of the phosphate or phenol moiety, direct alkylation or trifluoracetylation. Thin-layer chromatography with enzyme inhibition detection can be used as a rapid screening technique or to confirm results obtained by gas chromatography. Liquid chromatography has not been used much for the determination of organophosphorus compounds in foods.     

Field-portable flow-injection analysers for monitoring of air and water pollution

There has been a rapid growth in the development of field-portable analytical instrumentation capable of in-situ and real-time feedback of data from remote sites. Advances have been made in applications for many technologies aided by developments in electronics, computing and telecommunications systems. This report presents a brief review of these developments and particularly of portable flow-injection systems applied in both the liquid and gas phase modes of operation with potentiometric sensors and gas sensors of the tin-oxide semiconductor types.     

Determination of triazines and organophosphorus pesticides in water samples using solid-phase extraction.

Octadecyl (C18)-bonded porous silica was evaluated for the extraction of triazine and organophosphorus pesticides from natural water. The extraction results showed an effective performance when 11 of water was passed through small glass columns containing 500 mg of 50-100-microns C18 bonded porous silica. The adsorbed compounds were removed with ethyl acetate, evaporated to 200 microliters and determined by gas chromatography. The overall average recoveries were greater than 85% except for dimethoate and trichlorfon. Application of this procedure to the analysis of natural water samples gave results that agree well with those obtained by solvent extraction methods.     

Magnetic titanium oxide nanoparticles for hemimicelle extraction and HPLC determination of organophosphorus pesticides in environmental water

We report on a method for the extraction of organophosphorus pesticides (OPPs) from water samples using mixed hemimicelles and magnetic titanium dioxide nanoparticles (Fe₃O₄@TiO₂) modified by cetyltrimethylammonium. Fe₃O₄@TiO₂ nanoparticles were synthesized by a hydrothermal process and then characterized by scanning electron microscopy and Fourier transform IR spectrometry. The effects of the quantity of surfactant, extraction time, desorption solvent, pH value, extraction volume and reuse of the sorbent were optimized with respect to the extraction of OPPs including chlorpyrifos, dimethoate, and trichlorfon. The extraction method was applied to analyze OPPs in environmental water using HPLC along with UV detection. The method has a wide linear range (100–15,000 ng L^?1), good linearity (r?>?0.999), and low detection limits (26–30 ng L^?1). The enrichment factor is ~1,000. The recoveries (at spiked levels of 100, 1,000 and 10,000 ng L^?1) are in the range of 88.5–96.7 %, and the relative standard deviations range from 2.4 % to 8.7 %.

A piezoelectric detector for organophosphorus pesticides in the air

The concentration-time data obtained in kinetic analyses may be easily and conveniently interpreted by multiparametric curve-fitting. A new technique of kinetic analysis, in which the overall extent of reaction is monitored by following the variation with time of the difference between the temperature of a reaction mixture and that of a reference solution, is described. Both these techniques are illustrated with-data obtained in oximations of mixtures of propanal-and cyclohexanone. The results confirm the existence of the synergic effect reported by Siggia and Hanna.     

Determination of organophosphorus pesticides by thin-layer chromatography

Analysis for 13 common organophosphorus pesticides by thin-layer chromatography is described; 17 solvent systems were examined. With channel thin-layer chromatography, linear calibration graphs were obtained for the range 1-10 mug.     

A gold-based nanobeacon probe for fluorescence sensing of organophosphorus pesticides

A nanomaterials-based novel molecular beacon has attracted growing attentions in fluorescent assays as many nanomaterials possess excellent quenching efficiency. In this work, a gold-based nanobeacon probe was established to detect organophosphorus pesticides for the first time. The constructed gold-based nanobeacon acted as a signal indicator and could display the decreasing of the intensity in the presence of targets, which competitively bound to single strand DNA. To achieve a high sensitive probe, some parameters including solution pH, temperature and reaction time were investigated and optimized. The gold-based nanobeacon probe assay was proved to be rapid and sensitive to achieve a detection limit of 0.035 μM for isocarbophos, 0.134 μM for profenofos, 0.384 μM for phorate and 2.35 μM for omethoate, respectively. The prepared nanobeacon effectively reduced the background and improved the detection sensitivity and selectivity. The probe is stable, easy to operate and does not need sophisticated instruments. These features makes the probe feasible for screening trace organophosphorus pesticides in real samples.     

Optical leaky waveguide biosensors for the detection of organophosphorus pesticides

Organophosphorus (OP) pesticides can be rapidly detected by integrating organophosphorus hydrolase with an optical leaky waveguide biosensor. This enzyme catalyses the hydrolysis of a wide range of organophosphorus compounds causing an increase in the pH. Thus, the direct detection of OP is possible by monitoring of the pH changes associated with the enzyme's activity. This article describes the use of an optical, leaky waveguide clad with absorbing materials for the detection of OP pesticides by measuring changes in refractive index, absorbance and fluorescence. In the most effective configuration, a thick sensing layer was used to increase the amount of immobilized enzyme and to increase the light interaction with the sensing layer, resulting in a greatly enhanced sensitivity. The platforms developed in this work were successfully used to detect paraoxon and parathion down to 4 nM concentrations.     

Trends in the use of passive sampling for monitoring polar pesticides in water

The presence of polar pesticides in environmental waters is a growing problem. After application their migration into the aqueous phase is promoted by their high water solubility. Transport processes are usually complex and inputs are generally stochastic; this makes monitoring of this class of pesticides challenging using low volume spot samples of water. Recently there has been a trend to use passive samplers to monitor pesticides in river catchments as it is an in-situ time integrative sampling technique. The three main types of device used for this purpose are, Chemcatcher®, POCIS and o-DGT. This article reviews the fate and current state-of-the-art for monitoring polar pesticides in aqueous matrices. Principles and the theory of passive sampling and strategies for passive sampler design and operation are presented. Advances in the application of passive sampling devices for measuring polar pesticides are extensively critiqued; future trends in their use are also discussed.     

Use of SPME extraction to determine organophosphorus pesticides adsorption phenomena in water and soil matrices

Solid-phase micro extraction (SPME) coupled with GC enables rapid and simple analysis of organophosphorus pesticides in a range of complex matrices. Investigations were made into the extraction efficiencies from water of six organophosphorus insecticides (methamidophos, omethoate, dimethoate, parathion methyl, malathion, and parathion ethyl) showing a wide range of polarities. Three SPME fibres coated with different stationary phases, polydimethylsiloxane, polyacrylate, and carbowax-divinylbenzene (CW-DVB), were investigated. Water was spiked with the pesticides at concentrations from 1 to 0.01 µg mL-1, and the solutions used for optimization of the procedure. The CW-DVB fibre, with a 65 µm coating, gave the best performance. The optimized experimental conditions were sample volume 10 mL at 20°C, equilibration time 16 min, pH 5, and presence of 10% w/v NaCl. SPME analyses were performed on solutions obtained by equilibrating aqueous pesticide solutions with six certified soils with various physico-chemical characteristics. SPME data were also assessed by comparison with analyses performed by using conventional solid-phase extraction. Results indicate the suitability of SPME for analysis of pesticides in environmental water samples.     

固相微萃取-气相色谱-质谱联用分析环境水样中痕量有机磷农药

研究了固相微萃取(SPME) 气相色谱 质谱联用(GC MS)同时测定环境水样中二嗪农、甲基对硫磷、对硫磷和水胺硫磷4种有机磷农药(OPPs)的分析方法。选择聚丙烯酸酯(PA)萃取纤维,对SPME的条件如萃取时间、萃取溶液的pH值和离子强度、解吸温度、解吸时间和GC MS的条件进行了优化。对二嗪农和水胺硫磷方法线性范围为0.001～10μg L,对甲基对硫磷和对硫磷方法线性范围为0.001～100μg L。二嗪农、甲基对硫磷、对硫磷、水胺硫磷的检出限分别为0.015,0.020,0.013和0.039μg L。分析加标自来水、矿泉水和湖水样品,回收率在89.0%～102%之间,RSD在2.1%～14.1%之间。适合于环境水样中痕量OPPs的快速分析。     

Determination of atrazine and four organophosphorus pesticides in ground water using solid phase microextraction (SPME) followed by gas chromatography with selected-ion monitoring

A rapid, sensitive, and convenient method is presented for the determination of atrazine and four organophosphorus pesticides (OPP) in small (10 ml) samples of ground water. Samples are initially fortified with ethion (internal standard), then extracted without organic solvent using a 65-microm thickness polydimethylsiloxane/divinylbenzene (PDMS-DVB) solid-phase microextraction (SPME) fiber. The analytes collected are thermally desorbed in a heated gas chromatographic inlet, separated using a fused-silica capillary column, and detected using a mass selective detector in its selected-ion monitoring (SIM) mode. Two independent statistical procedures were used to evaluate the detection limits, which typically range between 2 and 8 microg l(-1) for these analytes. Method performance was also evaluated using "performance evaluation" samples, in which clean authentic ground waters were fortified to known concentrations with at least two of the analytes of interest. Sample-to-sample analysis time is approximately 30 min, making the new method ideal for "quick turn" determinations.     

A wireless magnetoelastic biosensor for the direct detection of organophosphorus pesticides

An organophosphorus (OP) pesticide sensor was fabricated by applying a pH-sensitive polymer coating and organophosphorus hydrolase (OPH) enzyme onto the surface of a magnetoelastic sensor, the magnetic analogue of the better-known surface acoustic wave sensor. Organophosphorus hydrolase catalyses the hydrolysis of a wide range of organophosphorus compounds, which changes the pH in the hydrogel. This article describes the application of the magnetoelastic sensor for the detection of OP pesticides by measuring the changes in viscoelasticity caused by the swelling/shrinking of the pH-responsive polymer when exposed to the pesticides. The sensor was successfully used to detect paraoxon and parathion down to a concentration of 1 x 10(-7) and 8.5 x 10(-7) M respectively.