Influence of plant growth regulating substances on transport and degradation of acephate and its metabolite methamidophos in tomato

The occurrence of pesticides in vegetables such as tomato poses an increasing attention to their potential risk to human health. In this study, acephate and its metabolite methamidophos were investigated for their transport and degradation in tomato cultivated in spiking nutrient solutions containing acephate at 1 mg/L. Acephate was taken up and transported via xylems with the concentrations of 41–145 μg/L in xylem sap at 2 and 8 cm above the roots in control treatment. The residue levels of methamidophos derived from acephate were in a range of 0–4.21 μg/L, being 0.00–3.73% of the parent acephate. The influence of three plant growth regulating substances, 1-naphthylacetic acid (NAA), glucose and phlorizin, on the transport and degradation of acephate and methamidophos in tomato was evaluated. All of these substances had positive effects on the transport of acephate and methamidophos in tomato xylem system. The NAA or glucose treatment promoted the degradation of acephate to methamidophos; however, with the addition of phlorizin, the concentrations of acephate were reduced in comparison to that under glucose treatment, suggesting that phlorizin would cause an inhibitory effect on the transport of acephate in tomato plant. These results may indicate an effective approach to reduce acephate and methamidophos residues in tomato.     

Enantioseparation and dissipation of acephate and its highly toxic metabolite methamidophos in pakchoi by supercritical fluid chromatography tandem mass spectrometry

Acephate is widely used in crops as racemate. However, the enantioselective dissipation of acephate enantiomers has not been investigated in pakchoi. A sensitive and effective approach was established for determining residues of acephate and its highly toxic metabolite methamidophos enantiomers by supercritical fluid chromatography tandem mass spectrometry. Baseline separations for their enantiomers were achieved by using a Chiralcel OD-H column. The optimal chromatographic conditions were obtained as follows: CO₂/ethanol (95/5) as mobile phase; flow rate, 3.0 mL/min; column temperature, 40°C. The mean recoveries (RSDs) of analytes were in the range of 77–83.1% (6.1–9.9%), 75.4–87.5% (9.3–13.2%), and 81.5–84.2% (7.1–13.4%) at three fortification levels (0.005, 0.05, and 0.5 mg/kg for each enantiomer) for interday assay (n = 18). The method was used to evaluate the enantioselective dissipation of acephate and methamidophos in pakchoi. S-acephate dissipated faster than R-acephate, while the concentration of R-methamidophos was higher than that of S-methamidophos during the entire study period. The results indicated that the R-enantiomer of acephate and methamidophos was preferentially enriched in pakchoi. The established analysis approach and the study data provided useful information for the rational use of acephate in agriculture.     

Determination of acephate and its degradation product methamidophos in soil and water by solid-phase extraction (SPE) and GC-MS

Acephate and its metabolite, methamidophos, are both highly polar organophosphorus pesticides (OPs) and are therefore highly soluble in water, which leads to difficulties when traditional methods of extraction, such as LLE (liquid–liquid extraction), are used. Solid-phase extraction (SPE) is a relatively new, highly versatile method, which has proven successful in many cases that were considered problematic in the past. In this study, several adsorbents (polymeric and silica based) and parameters are considered and modified to obtain maximum recovery. Maximum recoveries for acephate and methamidophos were found to be 90–95% and 85–90% respectively with Oasis HLB cartridges and methylene chloride as the elution solvent. In order to establish applicability and reliability, the matrix effect of several real water and solid (compost and soil) samples was evaluated. A 20–30% diminution of recovery is noted for some samples with a complex matrix containing a high amount of dissolved organic matter.     

GC-NPD investigation of the recovery of organonitrogen and organophosphorus pesticides from apple samples: The effect of the extraction solvent

Summary A gas chromatographic method employing a capillary column and a selective nitrogen/phosphorus detector (NPD) has been developed for the determination of organophosphorus (OP) and organonitrogen (NP) pesticides in horticultural samples (apples). The separation of sixteen pesticides and the internal standard was performed in thirteen minutes. The analytical characteristics of the method, including linear response ranges, detection limits, and reproducibility, have been studied using a 11 mixture of ethyl acetate and xylene as extraction solvent. The possibility of mutual interference between pesticides has also been studied. A procedure for the quantitative extraction of the sixteen pesticides from apple samples has also been developed; for fifteen of the pesticides recoveries >85% were obtained after 90 minutes extraction. The effect of different solvents both on recovery and on the sensitivity of the subsequent chromatography were also investigated. It was found that the sensitivity required must be considered when the solvent for sample treatment is selected.     

Residue determination of cyromazine and its metabolite melamine in chard samples by ion-pair liquid chromatography coupled to electrospray tandem mass spectrometry

A method has been developed for the sensitive and selective determination of cyromazine and its metabolite melamine in chard samples. Both compounds are small polar basic molecules, making their determination at residue levels complicated. The method involves an extraction procedure with phosphate buffer and methanol using high-speed blender, the addition of tridecafluoroheptanoic acid (TFHA) as ion-pair reagent and the injection of the five-fold diluted extract on liquid chromatography coupled to electrospray tandem mass spectrometry (LC–ESI–MS/MS). The method has been validated for chard samples, spiked at 0.05 and 0.5 mg kg⁻¹. Quantification was carried out by using matrix-matched standards calibration and recoveries were satisfactory, with mean values for cyromazine of 103% and 93%, and relative standard deviations lower than 7%. In the case of melamine, recoveries were 89% and 86%, with relative standard deviations lower than 13%. A limit of quantification of 0.05 mg kg⁻¹ was obtained for both compounds, with the limit of detection below 0.01 mg kg⁻¹. The method, with very little sample handling and good sensitivity, was applied to the rapid determination of low residue levels of these compounds in chards from field residue trials. All the quality controls included during the analysis were satisfactory with average recoveries of 92% and 78% for cyromazine and melamine, respectively.     

Identification of polycyclic aromatic hydrocarbons and methoxylated phenols in wood smoke emitted during production of charcoal

Summary A method for detection, quantification, and confirmation of 30 multi-class pesticide residues in fresh vegetables by gas chromatography-tandem mass spectrometry (GC-MS-MS) has been developed. The optimum ionization mode, electron impact (El-MS-MS) or chemical ionization (Cl-MS-MS), was used for different groups of pesticides in a single run. The residues were previously extracted from vegetables with dichloromethane. A 10μL aliquot of the extract can be injected in routine analysis without a clean up step when the glass liner is used with Carbofrit. Recovery efficiencies ranged 70–119% at the two different fortification levels studied and the relative standard deviation was <16.9% for all compounds. The limit of detection of each compound was 30 ng Kg⁻¹−6 μg Kg⁻¹. The proposed method was applied to the routine analysis of pesticides in vegetables grown in an important greenhouses area located in El Ejido (Almería, Spain).     

A new method for the quantitative analysis of organochlorine pesticides and polychlorinated biphenyls

A simple method is described for the quantitative determination of organochlorine pesticides and polychlorinated biphenyls (PCB's) in water at the sub-ppb level. A micro gas-phase extractor advantageously replaces other preconcentration and purification techniques. The extract is analyzed by capillary gas chromatography without further enrichment. The recovery at the ppb level was nearly 100% for organochlorine pesticides and more than 80% for PCB's. The complete procedure including sample preparation, steam distillation-extraction, and capillary gas chromatographic analysis is carried out in less than four hours.     

New clean-up method for gas chromatographic analysis of pyrethroid residues

Summary A fast and efficient method has been developed for clean-up of fenpropathrin and fluvalinate for gas chromatographic determination of their residues in crops, grain and soil. Charcoal (Darco-G-60) was used as adsorbent and the pyrethroids recovered by washing the adsorbent with hexane-acetone (9∶1). The method provides a clear filtrate with no interfering peaks in the chromatogram. Recoveries ranged 91.00–100%.     

Gas and liquid chromatography and enzyme linked immuno sorbent assay in pesticide monitoring of surface water from the western mediterranean (Comunidad Valenciana,Spain)

Summary A monitoring programme based on gas chromatography (NPD, ECD) using MSD for confirmatory purposes and coupled-column liquid chromatography was applied to the analysis of pesticide residues in surface water from a predominantly agricultural area of Spain (Comunidad Valenciana). Samples analysed by means of enzyme-linked immunosorbent assay gave similar results to those obtained by GC (MSD) for the determination of total triazines. The test employed had the advantages of a simple test procedure, short analysis time and high confirmatory value. Nevertheless, the multiresidue character, accuracy and unequivocal identification of individual pesticide residues of GC (MSD) make this technique the most appropriate for environmental monitoring programmes. In this monitoring programme about 200 samples were analysed between 1993–1994. 27 different pesticides were detected in 91 of these samples. The pesticides more frequently detected were dimethoate, methidathion, endosulfan A and B, endosulfan sulphate and pirimicarb. The highest concentrations found were 39.9 g L^–1 of dimethoate, 10.6 of pirimicarb and 10.6 of methidathion.     

A SPME-GC-MS approach for antivarroa and pesticide residues analysis in honey

Summary Results are presented that were obtained independently by two laboratories employing solid-phase micro extraction (SPME) for the analysis of pesticide residues in honey. The compounds Amitraz, Coumaphos, Cymiazole, Bromopropylate and Fluvalinate, used for chemitherapic treatment of beehives and other widely used agricultural insecticides, were extracted using a polydimethylsiloxane fiber of 100 μm thickness. The precision, accuracy, intervals of linearity and detection limits of the methodare discussed. Considering the rapidity and simplicity of this technique and, on the other hand, the difficulties arising from its application to a very complex matrix, SPME can certainly be considered a useful tool for the rapid screening of residues in honey.     

Development of an ultrasound‐assisted emulsification microextraction method for the determination of chlorpyrifos and organochlorine pesticide residues in honey samples using gas chromatography with mass spectrometry

A simple, rapid, and efficient ultrasound‐assisted emulsification microextraction method followed by gas chromatography mass spectrometry in selected ion monitoring mode was developed for the determination of organochlorine pesticides in honey samples. The type and volume of organic extraction solvent, pH, effect of added salt content, and centrifuging time and speed were investigated. Under the optimum extraction conditions, 30 μL of 1, 2‐dibromoethane (extraction solvent) was immersed into an ultrasonic bath for 1 min at 40°C. The limits of detection and quantification for all target pesticides were 0.003–0.06 and 0.01–0.2 ng/g_, respectively. The extraction recovery was 91–100% and the enrichment factors were 168–192. The relative standard deviation for the method was <6% for intraday (n = 6) and <8% for interday precision (n = 4). The proposed method was successfully applied for the analysis of organochlorine pesticides in honey samples.     

毛细管气相色谱法测定中药材中多种拟除虫菊酯农药残留量

研究了气相色谱法测定中药材中多种拟除虫菊酯类残留量的分析方法。样品经正己烷．丙酮混合液[V（正己烷）：V（丙酮）=1：1]提取,氟罗里硅土层析柱净化,采用毛细管色谱柱分离,GC-ECD可同时测定8种拟除虫菊酯类农药残留量,回收率为76．6％～104．2％。     

Determination of coumaphos, chlorpyrifos and ethion residues in propolis tinctures by matrix solid-phase dispersion and gas chromatography coupled to flame photometric and mass spectrometric detection

A new analytical method has been developed and successfully evaluated in routine application for the quantitative analysis of a selected group of organophosphate pesticides (coumaphos, chlorpyrifos and ethion) which can be found at trace levels in propolis tinctures (ethanolic propolis extracts); a valuable commodity used as raw material in the food and pharmaceutical industries for which there have been few attempts for pesticide residue analysis reported in the literature. The proposed methodology is based on matrix solid phase dispersion (MSPD) using aluminum sulfate anh. a novel dispersant material and subsequent column chromatography clean-up in silica gel prior to gas chromatography (GC) with both flame photometric detector (FPD) and mass spectrometry (MS) detection used for the routine quantification and identification of the residues, respectively. The limits of detection, for coumaphos, chlorpyrifos and ethion were below 26.0 μg/kg in FPD and 1.43 μg/kg for MS detection. Mean recoveries were in the range of 85-123% with RSD values below 13%, which suggests that the proposed method is fit for the purpose of analyzing pesticides in propolis tinctures containing high concentration of polyphenolics. The method has been successfully applied in our laboratory for the last 2 year in the analysis of real propolis tinctures samples.     

Extraction of acephate pesticide in environmental and agricultural samples by spectrophotometric method

In the present study, we have synthesis the azo dye for the reaction of p-amino antipyrine with HCl in NaNO₂ solution a 1:1 ​M ratio that was kept -5°C for 1–2 ​h, as result the absorption spectra observed at λ_max ​= ​460 ​nm. Beer’s law is obeyed over the awareness variety of 1 ​μg–100 ​μg ​mL^-1. The standard deviation and relative well-known deviation are 0.007 and 1.38%. The molar absorptivity and Sandell's sensitivity had been located to be 0.98 ​× ​10⁵ ​L ​mol^-1 ​cm^-1 and 0.99 ​× ​10^-3 ​μg ​cm^-2, respectively. Spectroscopy method used for the detection of Acephate pesticides on vegetable, fruit, soil, and water samples. FTIR method was used to consider and achieve structural information about the presented intermolecular interactions for vegetable samples. The eco-friendliness of the developed methods was assessed using the spectroscopy analytical tool on vegetables, fruit, soil, and water samples.     

Improved analytical procedure for determination of chlorinated pesticide residues in human serum using solid phase disc extraction (SPDE), single-step clean-up and gas chromatography

Summary An improved analytical methodology based on solid-phase disc extraction (SPDE) and a single-step clean-up on Florisil is proposed for a large number of organochlorine pesticide residues in serum. Extraction was performed following denaturation of proteins with formic acid after it was shown that it has no degradation effect on targeted analytes (α, β, γ-HCH isomers, HCB, DDT with its 5 analogues, endrin, aldrin, dieldrin, alachlor; heptachlor, heptachlorepaxide, α, β-endosulphan, endosulphansulphate, methoxychlor and mirex). Determination and quantification were by GC-ECD and GC-MS on two different, analytical capillary-columns using PCNB (pentachlonitrobenzene) and PCB 190 internal standards. Recoveries and limits of detection determined on pooled serum ranged 54–102% (for medium spiking level) and 10–50 pg ml⁻¹ serum respectively. Twenty-one individuals serum samples from the University Hospital of Antwerp were analysed and results were related to the ages of the donors. For compounds not detected by GC-MS, eventual coelution with PCBs in GC-ECD analysis was studied.     

Simultaneous extraction of norflurazon and oxadixyl residues from food crops with supercritical carbon dioxide

Summary Norflurazon and Oxadixyl residues have been analysed by HRGC-ECD after extraction from field-treated sugar cane and grapes using classical solid-liquid extraction or supercritical fluid extraction. The extraction techniques were compared; the results indicate the advantages of SFE as an alternative method for analysis of pesticides in these samples.     

Analysis of pesticide residues in tobacco with online size exclusion chromatography with gas chromatography and tandem mass spectrometry

An ultrasensitive method for the simultaneous analysis of pesticides residues in tobacco was developed with online size exclusion chromatography with gas chromatography and tandem mass spectrometry. Tobacco samples were extracted with the solvent mixture of cyclohexane and acetone (7:3, v/v) and centrifuged. Then, the supernatant liquors were injected directly into the online size exclusion chromatography with gas chromatography and tandem mass spectrometry without any other purification procedures after being filtered with a 0.22 μm organic phase filter. The matrix interferences were effectively removed and recoveries of most pesticides were in the range of 72–121%. Especially, for chlorothalonil, the analysis efficiency of this method was much more favorable than that of the general method, in which dispersive solid‐phase extraction was used as an additional purified procedure. In addition, the limits of quantitation of this method were from 1 to 50 μg/kg. Therefore, a rapid, cost‐effective, labor‐saving method was proposed in the present work, which was suitable for the analysis of 41 pesticide residues in tobacco.     

分子印迹固相萃取牛奶中甲胺磷

以甲胺磷为印迹分子、α-甲基丙烯酸为功能单体及三羟甲基丙烷三丙烯酸酯为交联剂,通过悬浮聚合法制备甲胺磷分子印迹聚合物(MIP)微球,并用该聚合物进行了牛奶中甲胺磷残留的固相萃取研究.静态吸附实验表明,在结构相似物乙酰甲胺磷和水胺硫磷为竞争底物存在下,MIP对甲胺磷有良好的吸附识别能力.在优化条件下,印迹分子的固相萃取回收率达96.4%,能够用于甲胺磷的富集,而空白聚合物却不具备这样的特性.当实际牛奶样品中甲胺磷、乙酰甲胺磷和水胺硫磷加标水平为100μg/kg时,甲胺磷回收率达87.4%,乙酰甲胺磷和水胺硫磷的回收率低于15%.结果表明分子印迹固相萃取对甲胺磷有很好的专一选择性,且回收率能够满足农药残留分析要求.在相同实验条件下,与C18固相萃取柱进行比较,分子印迹固相萃取的选择性及样品净化能力优势明显.     

High resolution chemically bonded fused-silica capillary gas chromatography of organochlorine insecticides and related compounds in arable soil samples

Electron capture gas chromatography with three chemically bonded fused-silica capillary columns (CB-FSCs), OV-17, OV-1701, and SE-52, was performed to evaluate peak separability of 28 organochlorine insecticides and related compounds. Relative retention times and relative peak heights to aldrin were measured and calculated. OV-17 CB-FSC showed the best separability among the three CB-FSCs employed and was applied to analysis of extracts from several soil samples with minimum clean-up procedure. The chromatograms obtained demonstrated steady baseline tracings free of interference. Residue data from soil samples were also tabulated.     

Supercritical fluid extraction of oxadixyl from food crops

Summary This work describes the study of a degradation curve of Oxadixyl in field-treated potato and tomato samples. The residues were extracted using classical and supercritical fluid (SFE) extraction methods and analyzed by HRGC/ECD. The extraction techniques were compared and the results indicate the advantages of using SFE as an alternative method for pesticide analyses in these samples.