Microwave-assisted extraction method for the determination of atrazine and four organophosphorus pesticides in oranges by gas chromatography (GC)

A simple and rapid microwave assisted extraction (MAE) method is presented for the determination of atrazine and four organophosphorus pesticides (parathionmethyl, chlorpyriphos, fenamiphos and methidathion) in orange peel. The experimental variables that affect the MAE method, such as temperature, sample quantity, extraction time, nature and volume of organic solvents, were optimized. The MAE method was optimized using an experimental design. The results suggest that temperature and sample quantity are statistically significant factors. It was concluded that the five pesticides could be efficiently extracted from 1.5-2.5 g of orange peel with 10 mL of hexane/acetone (1: 1) mixture at 90 degrees C in 9 min with microwave power set at 50% (475 W). After optimization these factors, recoveries ranged from 93 to 101% with a relative standard deviation ranging from 1 to 3%. The extracts were analyzed by gas chromatography with a nitrogen-phosphorus detector (GC-NPD).     

Microwave-assisted extraction method for the determination of atrazine and four organophosphorus pesticides in oranges by gas chromatography (GC)

A simple and rapid microwave assisted extraction (MAE) method is presented for the determination of atrazine and four organophosphorus pesticides (parathion-methyl, chlorpyriphos, fenamiphos and methidathion) in orange peel. The experimental variables that affect the MAE method, such as temperature, sample quantity, extraction time, nature and volume of organic solvents, were optimized. The MAE method was optimized using an experimental design. The results suggest that temperature and sample quantity are statistically significant factors. It was concluded that the five pesticides could be efficiently extracted from 1.5–2.5 g of orange peel with 10 mL of hexane/acetone (1?:?1) mixture at 90?°C in 9 min with microwave power set at 50% (475 W). After optimization these factors, recoveries ranged from 93 to 101% with a relative standard deviation ranging from 1 to 3%. The extracts were analyzed by gas chromatography with a nitrogen-phosphorus detector (GC-NPD).     

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).     

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).     

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.     

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.     

蔬菜、水果中12种限量有机磷农药残留量测定方法

建立了蔬菜、水果中12种限量有机磷农药的提取、净化及毛细管柱气相色谱测定法。目标农药经乙腈萃取,弗罗里硅土柱净化,浓缩后用带火焰光度检测器(FPD)的双塔双柱气相色谱测定,前柱(DB-17)定量,后柱(DB-1)定性。12种农药线性良好,线性相关系数大于0.9990,对蔬菜、水果添加0.01～0.1mg/kg的水平,12种有机磷的平均回收率在70.9%～119.9%之间,相对标准偏差0.12%～12%,本方法的最低检测限0.005～0.05mg/kg。     

Two organophosphorus pesticides: methyl parathion and dicapthon

Structural studies performed in this laboratory of organophosphorus pesticides continue with these related compounds. The –NO₂ groups of methyl parathion (systematic name: dimethyl 4‐nitrophenyl phosphorothioate, C₈H₁₀NO₅PS) and dicapthon (systematic name: 2‐chloro‐4‐nitrophenyl dimethyl phosphorothioate, C₈H₉ClNO₅PS) make dihedral angles of 10.67 (8) and 5.8 (1)°, respectively, with the planes of their attached rings, which accompanies angular distortion at the ring C atoms to which the –NO₂ groups are attached. Similar distortions are observed at the C atom to which the thiophosphate groups are attached. Significant differences in distances and angles around the phenolic O, versus the –OMe groups, explain why it is the site of hydrolysis for these compounds. A comparison of a torsion angle involving the thiophosphate group and phenolic O atom with similar pesticide structures is given and indicates steric influences on that angle.     

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.     

Determination of organophosphorus pesticides in honeybees after solid-phase microextraction

The solvation parameter model has been applied to the characterization of micellar electrokinetic chromatographic (MEKC) systems with mixtures of lithium dodecyl sulfate and lithium perfluorooctanesulfonate as surfactant. The variation in MEKC surfactant composition results in changes in the coefficients of the correlation equation, which in turns leads to information on solute-solvent and solute-micelle interactions. Lithium perfluorooctanesulfonate is more dipolar and hydrogen bond acidic but less polarizable and hydrogen bond basic than lithium dodecyl sulfate. Therefore mixtures of lithium dodecyl sulfate and lithium perfluorooctanesulfonate cover a very wide range of polarity and hydrogen bond properties, which in turn results in important selectivity changes for analytes with different solute properties.     

Quartz crystal microbalance determination of organophosphorus and carbamate pesticides

We have developed a quartz crystal microbalance (QCM) biosensor for the determination of organophosphorus and carbamate pesticides. A change in resonant frequency is observed as a result of mass adsorption, and we have used this as the basis for sensor development. Specifically, we have used a two-enzyme system (acetylcholine-esterase and choline oxidase) which converts acetylcholine to betaine producing hydrogen peroxide as a by-product. In a third enzyme reaction (peroxidase), the peroxide is able to oxidise benzidines (3,3′-diaminobenzidine) into an insoluble product that precipitates out and can adsorb to surfaces. Non-ionic surfactants have been used for the first time to enhance the surface deposition of suspended precipitate, thereby improving sensor sensitivity. Pesticides are known to inhibit esterase activity (thereby reducing the amount of QCM-detectable precipitate produced). We have shown that the QCM-enzyme sensor system can be used to determine carbaryl and dichlorvos down to 1 ppm.     

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.     

植物酯酶法检测有机磷农药残留量研究

对植物酯酶作为抑制剂检测有机磷农药的体系进行了研究,采用均匀设计法优化了检测条件;对可能影响酶活的干扰因素进行了分析;比较了7种有机磷农药对酶的抑制作用;建立了利用植物酯酶检测有机磷农药的方法,并应用于蔬菜样品中有机磷残留量检测。     

Separation of organophosphorus pesticides by using nano-liquid chromatography

In the present research, the separation of a series of organophosphorus pesticides (fensulfothion, fenamiphos, profenofos, fonofos, isofenphos, dialifos, sulprofos and prothiofos), by using nano-liquid chromatography (nano-LC) with UV detection is described. Three 100 μm ID capillary columns, packed with different silica-based stationary phases (CN, C₁₈, and phenyl), were investigated. Among these, the phenyl column offered the best results in terms of chromatographic performance, and was selected for pesticide analyses. Parameters, such as sample dilution solvent, injection volume, mobile phase composition and flow rate, were optimized in order to define the ideal experimental conditions. With the aim of improving sensitivity, on-column focusing of large injection volumes was applied: a sensitivity increase of circa 100-fold was attained, with limits of detection (LODs) and quantification (LOQs) within the 4.4–37.5 and 14.5–125.0 ng/mL ranges, respectively. The method was validated, with satisfactory results, through the measurement of the following parameters: limits of detection and quantification, precision, linearity and recovery. Finally, five different baby foods, previously fortified with a solution of the eight aforementioned pesticides, and then subjected to liquid–liquid extraction and solid-phase extraction clean-up, were analyzed.     

Analysis and behaviour of organophosphorus pesticides in a rice crop field

Summary A comprehensive analytical protocol for the determination of organophosphorus pesticides in the biotic and abiotic compartments of a rice crop field (Ebro delta, Spain) is described. This include two alternative clean-up procedures (Florisil column chromatography and Bio Beads SX-3 gel permeation chromatography) and gas chromatographic analysis with nitrogen-phosphorus and mass spectrometric detection. Among the pesticides identified, Fenitrothion was the most abundant with residue levels in sediment samples varying from 1–3 g/g in the first day of application to 0.5 g/g two days after, whereas in the water canals the concentrations were of 3–10 g/l, after aircraft application, with a rapid decrease several hours later. Half lives of Fenitrothion in water and sediment samples under natural conditions have been estimated to be lower than 1 day and between 1–1.5 days, respectively, with volatilization and microbial degradation accounting for this decay. The bivalves analysed in the coastal bays (Tapes semidecussatus, Ostrea edulis and Mytilus galloprovincialis) exhibited residue levels between 20–90 ng/g of organophosphorus pesticides, Fenitrothion being the most abundant organophosphorus pesticide. These levels are likely in the safe range for bivalves but not for other organisms such as crustacea, which are sensitive to water concentrations of 0.1 g/l.     

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.     

Comparison of microextraction procedures to determine pesticides in oranges by liquid chromatography-mass spectrometry

A liquid chromatographic–mass spectrometric method has been developed for the determination of bitertanol, carbendazim, fenthion, flusilazole, hexythiazox, imidacloprid, methidathion, methiocarb, pyriproxyfen and trichlorfon. Two procedures, based on stir bar sorptive extraction (SBSE) and matrix solid-phase dispersion (MSPD), have been evaluated for the extraction of these compounds in oranges. Their respective advantages and disadvantages are also discussed. The recoveries obtained by MSPD ranged from 47 to 96% and the relative standard deviations (RSDs) ranged from 1 to 15%, whereas with the SBSE method the recoveries were between 8 and 84% and the RSDs between 4 and 16%. Although, the limits of quantitation of most compounds are much better (0.001–0.05 mg kg⁻¹) by SBSE, it is not suitable to determine some polar pesticides as carbendazim, imidacloprid and trichlorfon. Results obtained by both methods were compared, in terms of sensitivity and selectivity, with a classical ethyl acetate extraction method, and the three methods were applied to analyze real samples. As MSPD is easier to perform, faster than the organic solvent extraction, and shows equal accuracy and resolution, its application for analyzing pesticides in oranges is recommended.