Isolation and concentration of organophosphorus pesticides from drinking water at the ng/L level, using macroreticular resin.

A screening method has been developed for determining organophosphorus pesticides at ng/L levels in drinking water. Sixteen organophosphorus pesticides, diazinon, diazinon-oxon, dimethoate, ronnel, beta-phosphamidon, methyl parathion, ethyl parathion, malathion, chlorpyrifos, fenitrothion, ruelene, methidathion, ethion, EPN, phosalone, and phosmet, were extracted by Amberlite XAD-2 resin from 100 and 200 L drinking water previously spiked with these pesticides. The pesticides were eluted from the XAD-2 resin with acetone-hexane (15+85). The concentrated extract was analyzed by gas chromatography using a nitrogen-phosphorus selective detector and by gas chromatography-mass spectrometry using selected ion monitoring. Recoveries at the 10 and 100 ng/L spiking levels were greater than 90%, except recoveries for dimethoate and phosphamidon were 37 and 42%, respectively. The analysis of 300 L Ottawa tap water showed no detectable amounts (less than 1 ng/L) of any of the 16 organophosphorus pesticides.     

Removal of Mixed Pesticides from Drinking Water System Using Surfactant-Assisted Nano-TiO2

The present study focused on the degradation of mixed pesticides using UV-induced photocatalytic degradation of lindane (1α,2α,3β,4α,5α,6β-hexachlorocyclohexane), methyl parathion (O,O-dimethyl-O-4-nitrophenyl phosphorothioate), and dichlorvos (2,2-dichlorovinyl-O-O-dimethyl phosphate). Different grades of TiO₂ were prepared through the acid route (AR), alcohol route (AlR), and surfactant route (SR) and their photocatalytic activity were compared with commercially available Degussa P-25 TiO₂. The rate of degradation of pesticides was high for TiO₂ prepared through the SR compared to the other three catalysts. The crystalline structure and morphology of SR TiO₂ was identified with scanning electron microscope, energy dispersive X-ray analyzer, UV, and transmission electron microscope analyses and was compared with that of Degussa P-25 TiO₂. Degradation studies of individual as well as mixed pesticides were carried out. The intermediate formed during the photodegradation of methyl parathion, lindane, and dichlorvos were identified by gas chromatography–mass spectrometry analysis.     

Sulfuric acid cleanup and KOH-ethanol treatment for confirmation of organochlorine pesticides and polychlorinated biphenyls: application to wastewater samples

The efficacy of sulfuric acid cleanup and KOH-ethanol hydrolysis confirmation was studied for 22 organochlorine pesticides and 2 polychlorinated biphenyls (PCBs). Mean recoveries for different treatment times are given. The method was applied to analysis of several wastewater samples by gas chromatography with electron capture detection. Organochlorine compounds were extracted by using separatory funnels and 15% diethyl ether in hexane as extractant. All the compounds studied could be analyzed except trifluralin, dichloran, dieldrin, and endrin, which were destroyed after treatment with concentrated H2SO4. The pesticides found most commonly in the samples analyzed were fenson, tetradifon, lindane, methoxychlor, and dicofol.     

Cutinase inhibition by means of insecticidal organophosphates and carbamates. 3. Oxidation of phosphorothionates by chloroperoxidase from Caldariomyces fumago

Chloroperoxidase (CPO) from Caldariomyces fumago combined with hydrogen peroxide and chloride proved to be most efficient for the transformation of organophosphorothionate pesticides, i.e., chlorpyrifos, chlorpyrifos-methyl, parathion, and parathion-methyl, into their more potent serine esterase inhibiting oxon analogues. Following CPO pre-oxidation steps, the detection limit of a recently described spectrophotometric cutinase assay could be increased by about 2 orders of magnitude as a consequence of increased inhibition rates of the organophosphates. This type of enzymatic oxidation is easier to perform and more efficient, as compared to bromine or N-bromosuccinimide, used for acetylcholine esterase (AChE) assay in water analyses, but is insufficient for complex matrices such as plant sample extracts. The performance of a complete assay, including sample preparation, oxidation, and inhibition, takes about 3 h. Performing oxidations of organophosphorus compounds, two significant anomalies were observed. Upon CPO oxidation, chlorpyrifos-methyl showed a very strong cutinase inhibition as compared to the corresponding oxon standard, and oxidized malathion, contrarily to malaoxon, revealed cutinase inhibition, which however obeyed a reversible reaction mechanism in contrast to the usually irreversible reactions of organophosphates. Except for methomyl, no significant effects of CPO oxidation on the inhibition strength of insecticidal carbamates could be detected. The applicability of the assay was tested with fruit samples spiked with chlorpyrifos at 0.2-0.5 mg/kg, thereby regarding the role of the latter as the pesticide detected most often in fruits. Mean recoveries ranged between 30-50%. An enhanced recovery of 84% was obtained for an apple juice sample spiked with parathion-methyl (0.5 mg/L).     

Describing movement of three pesticides in soil using a cstr in series model

The movement of methyl parathion, lindane, and atrazine in two successive soil layers has been described by a Continuously Stirred Tank Reactor (CSTR) model. In the first layer the concentration of each pesticide continuously decreased with time. In the second layer, a peak maxima appeared, whose position might be dependent on the water solubility of each pesticide and their adsorption by soil components. The physical process of transfer with the precipitating rainfall could be the main factor governing the transfer of pesticides, while the chemical, photochemical and biological processes of degradation acted uniformly on top of this process.     

Sorption of triazine and organophosphorus pesticides on soil and biochar

Sorption and degradation are the primary processes controlling the efficacy and runoff contamination risk of agrochemicals. Considering the longevity of biochar in agroecosystems, biochar soil amendment must be carefully evaluated on the basis of the target agrochemical and soil types to achieve agricultural (minimum impact on efficacy) and environmental (minimum runoff contamination) benefits. In this study, sorption-desorption isotherms and kinetics of triazine (deisopropylatrazine) and organophosphorus (malathion, parathion, and diazinon) pesticides were first investigated on various soil types ranging from clayey, acidic Puerto Rican forest soil (PR) to heavy metal contaminated small arms range (SAR) soils of sandy and peaty nature. On PR, malathion sorption did not reach equilibrium during the 3 week study. Comparison of solution-phase molar phosphorus and agrochemical concentrations suggested that degradation products of organophosphorus pesticides were bound on soil surfaces. The degree of sorption on different soils showed the following increasing trend: deisopropylatrazine < malathion < diazinon < parathion. While sorption of deisopropylatrazine on SAR soils was not affected by diazinon or malathion, deisopropylatrazine suppressed the sorption of diazinon and malathion. Deisopropylatrazine irreversibly sorbed on biochars, and greater sorption was observed with higher Brunauer-Emmett-Teller surface area of biochar (4.7-2061 mg g(-1)). The results suggested the utility of biochar for remediation of sites where concentrations of highly stable and mobile agrochemicals exceed the water-quality benchmarks.     

Simple analytical method for organophosphorus pesticide determination in unpolished rice, using removal of fats by zinc acetate

A rapid and simple method is developed for the determination of organophosphorus pesticides in unpolished rice. The new method incorporated acetonitrile-water (1 + 1) extraction, removal of fats by zinc acetate, and further cleanup on an activated charcoal chromatographic column. The higher fatty acids in the extract react rapidly with zinc acetate to form insoluble zinc carboxylates, which precipitate. Additional interferences were cleaned up on an activated charcoal chromatographic column, and organophosphorus pesticides adsorbed on the activated charcoal were eluted with acetone-hexane. Dimethoate is not retained on the activated charcoal and must be extracted with dichloromethane from the first acetonitrile-water eluate. Pesticides are measured by flame photometric gas chromatography. Recoveries from 50 g unpolished rice samples fortified with 5-50 micrograms diazinon, 6-30 micrograms parathion, 8-40 micrograms fenitrothion and IBP, 10-50 micrograms dimethoate and fenthoate, 20-100 micrograms malathion, or 40-200 micrograms EPN ranged from 75.7 to 95.8%.     

Determination of water-soluble polyphenolic compounds in commercial herbal teas from Lamiaceae: peppermint, melissa, and sage

Chromatographic techniques (HPLC and HPTLC) were used for qualitative and quantitative determination of eriocitrin, luteolin 7-O-rutinoside, luteolin 7-O-beta-glucuronide, lithospermic acid, rosmarinic acid, and methyl rosmarinate together with other known compounds in commercial herbal teas from the Lamiaceae family: peppermint leaf (Menthae piperitae folium), melissa leaf (Melissae folium), and sage leaf (Salviae officinalis folium). Contents of analyzed compounds in infusions, the most popular forms, were established using a C18 column with acetonitrile-water-formic acid as a mobile phase. The HPLC method was validated for linearity, precision, and accuracy. Luteolin 7-O-beta-glucuronide and lithospermic acid were identified as new Mentha x piperita compounds. The investigated herbal teas delivered polyphenols in high amounts, up to 182.2 mg for the infusion of one peppermint tea bag.     

Comparative study of methods for the extraction of eleven organophosphorus pesticide residues in rice.

Several extraction methods are compared for the simultaneous analysis of organophosphorus pesticides in unpolished rice. Four stationary phases were used for the subsequent gas-liquid chromatographic (GLC) determination of the selected pesticides. Using 3 different GLC columns, 11 pesticides were completely separated and identified. The efficiency of the cleanup and the sensitivity of the analytical method were evaluated by using powdered unpolished rice samples fortified with the pesticides and also wheat and dried bean samples. Average recoveries ranged from 74.7% for disulfoton to 97.4% for malathion in unpolished rice and from 68.1% for disulfoton to 108.3% for malathion in other crops. The method described is applicable to the analysis of selected organophosphorus pesticide residues in unpolished rice, wheat, buckwheat, and dried beans.     

基于构建微生物传感器的甲基对硫磷降解菌的分离鉴定及其降解特性研究

有机磷农药是目前环境中残留量最多的农药之一,对其残留量的检测及降解机制的研究对于环境污染及生态修复具有重要意义。微生物传感器由生物学元件与换能器构成,因具有成本低廉、易于微型化及选择性高等特点而被广泛应用于各种生化物质的分析和检测。本文从长期受农药污染的土壤中分离出4株能以甲基对硫磷为碳源生长的菌株,根据形态特征和16S r RNA基因序列同源性分析,对4株降解菌进行鉴定,利用高效液相色谱测定降解率,选取降解率最高的1株菌进行降解机制研究,以期将其应用于测定环境中甲基对硫磷残留的电位型微生物传感器的构建。结果表明,在甲基对硫磷初始浓度50 mg·L-1、30℃、p H 7.0的培养条件下培养7 d,4株菌对甲基对硫磷的降解率均在78%以上,其中1株菌的降解效率可达100%。16S r RNA基因序列测定表明,该菌株属于克雷伯氏菌属,命名为Klebsiella sp.MP-6。利用液相色谱-质谱联用对其降解产物的研究表明,菌株MP-6水解甲基对硫磷主要产生二甲基硫代磷酸(dimethyl thiophosphoric acid,DMTP)和对硝基苯酚(p-nitrophenol,PNP),极少部分PNP通过产生4-硝基邻苯二酚(4-nitrocatechol,4-NC)和1,2,4-苯三酚(1,2,4-BT)进一步代谢。结果表明,基于测定中间产物对硝基苯酚(p-nitrophenol,PNP)的电位响应信号,该菌株适用于构建测定海水及土壤等环境中有机磷农药的微生物传感器。     

Development of a solid-phase extraction coupling chemiluminescent enzyme immunoassay for determination of organophosphorus pesticides in environmental water samples

Solid-phase extraction (SPE) and direct competitive chemiluminescence enzyme immunoassay (dcCL-EIA) were combined for the detection of organophosphorus pesticides (OPs) in environmental water samples. dcCL-EIA based on horseradish peroxidase labeled with a broad-specificity monoclonal antibody against OPs was developed, and the effects of several physicochemical parameters on dcCL-EIA performance were studied. SPE was used for the pretreatment of water samples to remove interfering substances and to concentrate the OP analytes. The coupling of SPE and dcCL-EIA can detect seven OPs (parathion, coumaphos, phoxim, quinalphos, triazophos, dichlofenthion, and azinphos-ethyl) with the limit of quantitation below 0.1 ng/mL. The recoveries of OPs from spiked water samples ranged from 62.5% to 131.7% by SPE-dcCL-EIA and 69.5% to 112.3% by SPE-HPLC-MS/MS. The screening of OP residues in real-world environmental water samples by the developed SPE-dcCL-EIA and their confirmatory analysis using SPE-HPLC-MS/MS demonstrated that the assay is ideally suited as a monitoring method for OP residues prior to chromatographic analysis.     

Collaborative study of an extension of the Mills et al. method for the determination of pesticide residues in foods.

Fifteen laboratories collaboratively determined parathion, o,p'-DDT, p,p'-DDT, and p,p'-DDE in kale, and lindane, dieldrin, heptachlor epoxide, and p,p'-DDE in eggs, using electron capture gas-liquid chromatography (potassium chloride thermionic detector for parathion). Pesticide levels ranged from 0.033 ppm heptachlor epoxide to 3.32 ppm p,p'-DDT. Mean recoveries (+/- standard deviations) were: parathion 91+/-15%, o,p'-DDT 99+/-8%, P,P'-DDT 97+/-8%, lindane 94+/-4%, dieldrin 106+/-8%, heptachloro epoxide 106+/-5%, p,p'-DDE 94+/-8% in eggs and 101+/-9% in kale. The methods have been adopted as official first action.     

Capillary gas chromatography with atomic emission detection for pesticide analysis in soil samples

A method for the simultaneous determination of 10 pesticides (organochlorines, organophosphorus compounds, and pyrethrins) in soils using capillary gas chromatography with atomic emission detection (GC-AED) is reported. Soil samples are first "cleaned-up" with 25 mL of an ascorbic acid solution (pH 2.15). The aqueous phase is extracted with ethyl acetate, and the solid residue is then extracted twice with 10 mL of ethyl acetate. The three resultant organic extracts are combined, concentrated to dryness, and reconstituted in 1 mL of acetone. The pesticides are selectively detected by monitoring chlorine and bromine in the first run and sulfur emission line wavelength in the second run. Each chromatographic run takes 19 min. Detection limits are between 25 and 75 pg, depending on the compound, which corresponds to 1.7 and 5.0 ng/g in the soil samples, respectively. Recoveries of the pesticides from spiked preparations result in an overall mean recovery of 95.3% (n = 120) at fortification levels ranging from 10 to 60 ng/g, depending on the compound. The method is reliable and can be useful for routine monitoring in soils.     

Determination of ampicillin in serum by using simple ultrafiltration technique and liquid chromatographic analysis

A new liquid chromatographic method for determination of ampicillin in canine and equine serum has been developed. The serum sample (500 microL) is vortex-mixed with 20% ethanol (500 microL) and filtered using a 30,000 molecular weight cutoff microseparation tube to separate high molecular weight solutes following low-speed centrifugation. Ampicillin is then separated from other serum components by reverse phase ion-pair liquid chromatography (LC). The ultraviolet (UV) absorbance of the column effluent is monitored at 230 nm. Recoveries of ampicillin from canine serum spiked at concentrations of 10, 40, and 60 micrograms/mL were 93.1, 100.9, and 87.8%, respectively, with coefficients of variation (CVs) of 2.91, 3.08, and 4.08%, respectively. Recoveries of ampicillin from equine serum spiked at the same concentrations were 91.6, 90.1, and 88.7%, respectively, with CVs of 3.03, 2.61, and 3.35%, respectively. The limit of detection for ampicillin by this method is less than 0.5 micrograms/mL serum.     

Analysis of organophosphorus pesticides in honeybee by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

Pesticides applied in extended agricultural fields may be controlled by means of bioindicators, such as honeybees, in which are the pesticides bioaccumulate. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) experiments with positive (PI) and negative (NI) ion modes were optimized for the analysis of 22 organophosphorus pesticides in honeybee samples. The extraction required 3 g of sample, which was extracted with acetone. The extract was purified with coagulating solution and reextracted with Cl(2)CH(2). Pesticides studied could be detected by both ionization modes except for parathion, parathion-methyl, and bromophos, which did not give signals in PI mode, and triazophos, which was not detected in NI mode. Fragmentation voltage and vaporizer temperature were optimized to achieve the highest sensitivity. The spectra profile of each pesticide in PI mode showed the [M + H](+) ion as the main signal, whereas in NI mode only fragment ions were shown. The detection limit obtained in selected ion monitoring mode ranged from 1 to 15 microg kg(-1). The average recoveries from spiked honeybees at various concentration levels (0.5-5 mg kg(-1)) exceeded 65% with relative standard deviations of 4-15%. The method was applied to real samples, in which residues of coumaphos and dimethoate were detected.     

Identification by HPLC-DAD and HPLC-MS analyses and quantification of constituents of fennel teas and decoctions

Qualitative and quantitative differences among the constituents in various fennel (Foeniculum vulgare Mill., family Apiaceae) teas prepared by classical infusion, microwave decoction, and dissolution are reported. Different commercial starting materials, such as fruit (unbroken and crushed), four herbal teas, and two instant herbal teas were evaluated. Chlorogenic acid (1), quercetin-3-O-beta-D-glucuronide (2), p-anisaldehyde (3), and trans-anethole (4) were identified by HPLC-DAD and HPLC-MS as constituents of fennel teas. No coumarins, which are characteristic constituents of plants of Apiaceae family, were found. Trans-anethole (4), the main constituent of the essential oil, was present in all teas. In addition p-anisaldehyde (3), a degradation product of trans-anethole, was also identified in all teas with the exception of two samples. Chlorogenic acid (1) and quercetin-3-O-beta-D-glucuronide (2) were also present in all teas. In addition, minor unidentified flavonol constituents were found in two teas. Quality, activity, and safety of the content of the investigated preparations are also discussed.     

Automatic method for the determination of Folin-Ciocalteu reducing capacity in food products

In the present work, an automatic flow procedure based on multi-syringe flow injection analysis was developed for the assessment of Folin-Ciocalteu reagent (FCR) reducing capacity in several types of food products using gallic acid as the standard. Different strategies for mixing of sample and reagent were tested (continuous flow of FCR, merging zones, and intercalated zones approaches); lower reagent consumption and higher determination throughput were attained for the merging zones approach (100 microL of sample+100 microL of FCR). The application of the proposed method to compounds with known antioxidant activity (both phenolic and nonphenolic) and to samples (wines, beers, teas, soft drinks, and fruit juices) provided results similar to those obtained by the conventional batch method. The detection limit was 0.6 mg L-1, and the determination frequency was about 12 h-1. Good repeatability was attained (RSD<1.3%, n=10).     

Gas chromatographic-electron capture detection method for determination of 29 organochlorine pesticides in finished drinking water: collaborative study

A joint U.S. Environmental Protection Agency/AOAC interlaboratory method validation study was conducted on EPA Method 508, Determination of Chlorinated Pesticides in Water by Gas Chromatography with an Electron Capture Detector, to determine the mean recovery and precision for analyses of 29 pesticides in reagent water and finished drinking water. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with 29 pesticides at 6 concentration levels, as 3 Youden pairs. Eleven volunteer laboratories extracted the spiked test waters with methylene chloride, performed a solvent exchange with methyl tert-butyl ether, and analyzed an aliquot of each extract by gas chromatography with electron capture detection. Results were analyzed using an EPA computer program, interlaboratory Method Validation Study (IMVS), which measured recovery and precision for each of the 29 pesticides and compared the performance of the method between water types. Method 508 was judged acceptable for all analytes tested. Only 3 analytes (alpha-chlordane, 4,4'-DDE, and methoxychlor) exhibited practical significant matrix effects. The method has been adopted official first action.     

Analysis of agricultural residues on tea using d-SPE sample preparation with GC-NCI-MS and UHPLC-MS/MS

This study presents new sample preparation and analytical procedures for the quantification of pesticides on processed tea leaves. The new method includes tea extraction and dispersive solid phase extraction (d-SPE) to prepare gas chromatography (GC) and ultrahigh-performance liquid chromatography (UHPLC)-ready samples, providing a fast and cost-effective solution for time-sensitive industrial analysis to fulfill regulatory requirements. Both GC-negative chemical ionization mass spectrometry (GC-NCI-MS) and UHPLC-tandem mass spectrometry (UHPLC-MS/MS) were employed to produce highly sensitive and reproducible data. Excellent limits of detection (typically below 1 μg/kg for GC and 10 μg/kg for UHPLC), wide linearity ranges, and good recoveries (mostly >70%) were achieved on the selected pesticides. Twenty-seven tea samples purchased from local grocery stores were analyzed using the newly developed methods. Among the pesticides analyzed, endosulfan sulfate and kelthane were the most frequently detected by GC-NCI-MS and imidacloprid and acetamiprid by UHPLC-MS/MS in these teas. The samples were found to be relatively clean, with <1 mg/kg of total pesticide residues. The organic-labeled teas were significantly cleaner than nonorganic ones. The cost per gram of tea did not correlate with pesticide residue levels detected.     

Direct determination of p-nitrophenyl substituent organophosphorus nerve agents using a recombinant Pseudomonas putida JS444-modified Clark oxygen electrode

A microbial biosensor for rapid, sensitive, selective, and cost-effective determination of the total content of organophosphorus nerve agents with p-nitrophenyl substituent is reported. The biosensor consisted of genetically engineered PNP-degrader Pseudomonas putida JS444 expressing organophosphorus hydrolase (OPH) on its cell surface immobilized on a dissolved oxygen electrode. Surface-expressed OPH catalyzed the hydrolysis of organophosphorus pesticides with p-nitrophenyl substituent such as paraoxon, methyl parathion, and parathion to release p-nitrophenol that was oxidized by the enzymatic machinery of Pseudomonas putida JS444 to carbon dioxide while consuming oxygen. The oxygen consumption was measured and correlated to the concentration of organophosphates. The sensor signal and response time were optimized with 0.086 mg dry weight of cell and operating in 50 mM pH 7.5 citrate-phosphate buffer with 50 microM CoCl(2) at room temperature. When operated at optimized conditions, the biosensor measured as low as 55 ppb of paraoxon, 53 ppb of methyl parathion, and 58 ppb of parathion without interference from most phenolic compounds and other commonly used pesticides, such as atrazine, coumaphos, sutan, sevin, and diazinon. The operational life of the microbial biosensor was approximately 5 days when stored in the operating buffer at 4 degrees C.