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PubMed2003

Comprehensive solid-phase extraction method for persistent organic pollutants. Validation and application to the analysis of persistent chlorinated pesticides.

The Centers for Disease Control and Prevention (CDC) is involved in many epidemiological studies regarding the measurement of chlorinated pesticides and polychlorinated biphenyls in specimens obtained from humans. In addition to these commonly determined analytes, there is a need to include additional persistent organic pollutants (POPs) in our analyses, which further stresses the analyses because sample volumes remain small. Thus, a single method of analysis for all POPs in human serum is needed. CDC has recently developed a semiautomated and comprehensive solid-phase extraction method for POPs. The method is comprehensive since it was optimized for the extraction of many different POP compound classes. We then developed a purification and fractionation scheme that allows (a) separation of different compound classes by particular functionalities and (b) purification of those fractions to remove coextracted interferences. This paper describes the first step in the semiautomated comprehensive extraction and multiple fractionation method developed by CDC for monitoring POPs. In this paper, we validate the analysis of the persistent chlorinated pesticides, a compound class difficult to examine because of their structural diversity, in human plasma. The method was validated against an existing CDC method by using a spiked quality-control serum pool. The concentrations determined for all analytes using both methods were within 2%-14% relative standard deviations. A multilevel (i.e., 3-4 point) matrix spike showed good linearity for the analytes tested (r2 = 0.978-0.999). The method was then applied to 40-year-old archived plasma samples for the quantitative analysis of selected chlorinated pesticides. Mean recoveries of the 13C-labeled internal quantification standards ranged from 64% to 123% for the 11 monitored pesticides. The overall method proved to be robust by handling old coagulated plasma samples. It allowed faster throughput of samples than our previous methods and provided cleaner samples with less frequent interferences or background as analyzed by high-resolution mass spectrometry. The method represents a preliminary step in establishing an automated, comprehensive multiresidue analysis method for POPs in human serum.

Automation↗
PubMed2006

The detection of nitro pesticides in mainstream and sidestream cigarette smoke using electron monochromator-mass spectrometry.

Over the past decade, electron monochromator-mass spectrometry (EM-MS) has been shown to be a selective and sensitive technique for the analysis of a wide variety of electrophilic compounds in complex matrixes. Here, for the first time, three different dinitroaniline pesticides, flumetralin, pendimethalin, and trifluralin, have been shown to be present in both mainstream and sidestream tobacco smoke using an EM-MS system. A number of cigarettes were tested that included three pure-tobacco-type cigarettes, an experimental reference cigarette, and 11 commercial cigarettes. Due to the complexity of the smoke particulate matter, the pesticides were identified only after each sample was subjected to a multistep cleanup process that included phenyl solid-phase extraction; an acid wash; aminopropyl solid-phase extraction; and finally, normal phase LC fractionation. All cigarette types tested showed the presence of the three pesticides in the tobacco smoke, with flumetralin ranging from trace levels up to 37 (+/- 9) ng/cig, pendimethalin ranging from trace levels up to 10.4 (+/- 0.6) ng/cig, and trifluralin ranging from trace levels up to 47 (+/- 17) ng/cig. Acute toxicity information is presented for the three pesticides.

Aniline Compounds↗
PubMed2004

Distribution and toxicity of sediment-associated pesticides in agriculture-dominated water bodies of California's Central Valley.

The agricultural industry and urban pesticide users are increasingly relying upon pyrethroid insecticides and shifting to more potent members of the class, yet little information is available on residues of these substances in aquatic systems under conditions of actual use. Seventy sediment samples were collected over a 10-county area in the agriculture-dominated Central Valley of California, with most sites located in irrigation canals and small creeks dominated by agricultural effluent. The sediments were analyzed for 26 pesticides including five pyrethroids, 20 organochlorines, and one organophosphate. Ten-day sediment toxicity tests were conducted using the amphipod Hyalella azteca and, for some samples, the midge Chironomus tentans. Forty-two percent of the locations sampled caused significant mortality to one test species on at least one occasion. Fourteen percent of the sites (two creeks and four irrigation canals) showed extreme toxicity (>80% mortality) on at least one occasion. Pyrethroid pesticides were detected in 75% of the sediment samples, with permethrin detected most frequently, followed by esfenvalerate > bifenthrin > lambda-cyhalothrin. Based on a toxicity unit analysis, measured pyrethroid concentrations were sufficiently high to have contributed to the toxicity in 40% of samples toxic to C. tentans and nearly 70% of samples toxic to H. azteca. Organochlorine compounds (endrin, endosulfan) may have contributed to the toxicity at a few other sites. This study provides one of the first geographically broad assessments of pyrethroids in areas highly affected by agriculture, and it suggests there is a greater need to examine sediment-associated pesticide residues and their potential for uptake by and toxicity to benthic organisms.

Agriculture↗
PubMed2005

Gas-phase concentrations of current-use pesticides in Iowa.

Local and regional atmospheric transport of current-use pesticides is an important source of these compounds to nontarget plants and ecosystems. Current-use pesticides were measured at urban, rural, and suburban sites in eastern Iowa during 2000-2002. The most detected compounds were hexachlorobenzene and trifluralin, which were found in 89% and 78% of the samples, respectively. As expected, many pesticides showed a strong seasonal trend with the most detections and highest concentrations occurring during the spring and early summer. The average detected concentrations of five heavily used herbicides were 0.52 ng/ m3 for trifluralin, 4.6 ng/m3 for acetochlor, 2.3 ng/m3 for metolachlor, 1.1 ng/m3 for alachlor, 1.7 ng/m3 for pendimethalin, and 1.2 ng/m3 for atrazine. The most frequently detected insecticides were phorate and chlorpyrifos, which were found in 20% and 19% of the samples, respectively. The average phorate and chlorpyrifos concentrations were 25 ng/m3 and 1.0 ng/m3, respectively. The maximum phorate concentration, the highest measured for all pesticides, was 91.2 ng/m3. The most frequently detected current-use fungicides were chloroneb and etridiazole, which were found in 14% and 10% of the samples, respectively.

Air Pollutants↗
PubMed2006

Prioritization of pesticide environmental transformation products in drinking water supplies.

Receiving waters within catchments may be exposed to many different transformation products following the application of pesticides. As environmental waters are abstracted for drinking water treatment these compounds may pose a risk to human health. This paper describes a prioritization approach for identifying the most important transformation products in drinking water sources. The approach can be applied to different geographical areas that have suitable pesticide usage data. The risk based approach incorporates data on pesticide usage and toxicity as well as transformation product formation, mobility, and persistence. The application of the approach is illustrated for two geographical areas that have good quality pesticide usage data: Great Britain and California. The transformation products with the highest risk index and a complete experimentally derived data set for Great Britain were 3,5,6-trichloro-2-pyridinol, thifensulfuron acid, and kresoxim-methyl acid and for California were carbendazim, aldicarb sulfoxide, and RP30228.

California↗
PubMed2001

Occurrence and spatial and temporal distribution of pesticide residues in groundwater of major corn-growing areas of Greece (1996-1997).

During 1996-1997, residues of selected pesticides were monitored, at 3-month intervals, in 80 wells, including both irrigation and drinking water wells, distributed among the main corn-growing areas (Pieria, Thessaloniki, Serres, Kavala, and Evros) of Greece. Pesticide residues were found in 48% of the wells; however, in most cases residues were very low ranging from LOQs (quantification limits of the analytical methods) to <0.1 microg/L, while in 11% (nine wells) pesticide residues higher than 0.1 microg/L were present. Most of the latter wells were found in Evros and specificallythe Ardas Valley. The frequency of occurrence, in descending order, was atrazine > DEA > alachlor = metolachlor; however, the order of descending concentrations was atrazine > metolachlor > DEA > alachlor. The occurrence and the spatial and temporal distribution patterns of pesticide residues indicate that at the present the situation of groundwater quality is favorable throughout the corn-growing areas of Greece with the exception of the Ardas Valley.

Acetamides↗
PubMed2001

Multiresidue screening of pesticides in fruits using an automatic solid-phase extraction system.

About 20 pesticides were determined in lyophilized fruits using a semiautomatic multiresidue method, based on solid-phase extraction (SPE) with a silica column. The lyophilization of the sample, besides the SPE procedure selected, provided clean extracts despite the complexity of the matrixes studied. In addition, the lyophilization process allows sample preservation for at least three months without changes in the concentrations of the pesticides. Determination and quantitation of organochlorine and pyrethroid residues was carried out using a gas chromatograph equipped with an electron capture detector (GC-ECD), and a mass spectrometric detector (GC-MS) was used for confirmation purposes. Organochlorine pesticides provided average recoveries (spiked at three concentration levels in eight different fruits) near 93 +/- 4%, being lower (89 +/- 8%) for pyrethroids as a consequence of their higher degradation and interaction with the sample matrix. On the other hand, the detection limits achieved for all pesticides (0.5-8 ng per g of lyophilized fruit) allow their determination at the MRLs established by the European Union, with good precision ( approximately 5%). Finally, from the 100 different fruits screened, only 10 positive responses were obtained, which were further confirmed by GC-MS.

Automation↗
PubMed2001

Multiresidue method for the analysis of pesticide residues in fruits and vegetables by accelerated solvent extraction and capillary gas chromatography.

An analytical procedure using accelerated solvent extraction and capillary gas chromatography with electron capture and flame photometric detections was developed to simultaneously determine residues of different pesticides in fruits and vegetables. Single laboratory validation of the method was carried out for 28 compounds selected from eight pesticide classes, in blank and fortified samples of fresh pear, cantaloupe, white potato, and cabbage. The method had to meet specific established validation criteria for regulatory purposes applicable to our laboratory. At each of the two fortification levels studied, 24 of the 28 pesticides gave recoveries of more than 70% with a coefficient of variation of less than 10%. With respect to existing procedures, the method showed acceptable limits of detection (from 0.0019 to 0.14 microg/g depending on the pesticide and matrix) while minimizing environmental concerns, time, and labor.

Chromatography, Gas↗
PubMed2001

Focused microwave assistance for extracting some pesticide residues from strawberries into water before their determination by SPME/HPLC/DAD.

A novel and simple method for the determination of some pesticide residues in strawberries using both focused microwave-assisted extraction (FMAE) and solid-phase micro extraction (SPME), coupled with high-performance liquid chromatography (HPLC), has been developed. The pesticides were first extracted from strawberries with water and the assistance of focused microwaves at 30 W for 7 min. Then, an aliquot of the resulting aqueous extract was subjected to SPME with a 60-microm thick poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber for 45 min at room temperature, with the solution being stirred at 1000 rpm. The extracted pesticides on the SPME fiber were desorbed into the SPME/HPLC interface for quantitative analysis with a diode array detector (DAD). The whole sample pretreatment procedure before chromatographic analysis did not use any organic solvents or involve any blending or centrifugation steps. The five compounds (carbendazim, diethofencarb, azoxystrobine, napropamide, and bupirimate) were chosen because they cannot be analyzed easily by GC. The efficiency of this relatively fast procedure was comparable to that of previously reported methods, with detection limits at low microg/kg levels and linear responses in the range from 0.05 to 1 mg/kg of pesticide in strawberries, with RSDs between 3 and 7.3%, depending on the analyte. In all but one case results obtained by this method for field-incurred samples were comparable to those obtained with traditional methods.

Chromatography, High Pressure Liquid↗
PubMed2002

Modeling of single-step and multistep adsorption isotherms of organic pesticides on soil.

The aim of this study was to investigate the sorption behavior and mechanisms of the organic pesticides on soil. To establish the sorption isotherms of six commonly used pesticides (acetochlor, atrazine, diazinon, carbendazim, imidacloprid, and isoproturon), laboratory equilibrium studies were performed at extended concentration ranges on brown forest soil using the batch equilibrium technique. The pesticide concentrations in the equilibrated liquid phase were quantified with high-performance liquid chromatograph by ultraviolet detection. The adsorption processes could be described by a single-step (Langmuir) isotherm for acetochlor and carbendazim, by a two-step curve for diazinon, isoproturon, and atrazine, and by a three-step curve for imidacloprid. A nonlinear mathematical model-derived from the Langmuir equation-has been developed that represents well the detected single-step and multistep shaped adsorption isotherms. The interpreted model was found to fit the experimental data well and allows the description of the adsorption profile with great precision. The altered adsorption activity, which was indicated by the step arising on the plot, may represent the existence/occurrence of a different specific type of adsorption mechanism. This binding force starts to operate simultaneously at a critical concentration of solute in the studied soil-pesticide system. The parameters calculated from the equation provide an opportunity to estimate the extent of absorption constant, adsorption capacity, and concentration limit characteristic to the measured stepwise isotherms.

Adsorption↗
PubMed2003

Assessment of pesticide residues in honey samples from portugal and Spain.

Fifty samples of honey collected from local markets of Portugal and Spain during year 2002 were analyzed for 42 organochlorine, carbamate, and organophosphorus pesticide residues. An analytical procedure based on solid-phase extraction with octadecyl sorbent followed by gas chromatography-mass spectrometry (GC-MS), for organochlorines, and by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), for organophosphorus and carbamates, has been developed. Recoveries of spiked samples ranged from 73 to 98%, except for dimethoate (40%), with relative standard deviations from 3 to16% in terms of repeatability, and from 6 to 19% in terms of reproducibility. Limits of quantification were from 0.003 to 0.1 mg kg(-)(1). Most of the pesticides found in honey were organochlorines. Among them, gamma-HCH was the most frequently detected in 50% of the samples, followed by HCB in 32% of the samples and the other isomers of HCH (alpha-HCH and beta-HCH) in 28 and 26% of the samples, respectively. Residues of DDT and their metabolites were detected in 20% of the samples. Of the studied carbamates, both methiocarb and carbofuran were detected in 10% of the samples, pirimicarb in 4% and carbaryl in 2%. The only organophosphorus pesticides found were heptenophos in 16%, methidathion in 4%, and parathion methyl in 2% of honey samples. Results indicate that Portuguese honeys were more contaminated than Spanish ones. However, honey consumers of both countries should not be concerned about the amounts of pesticide residues found in honeys available on the market.

Carbamates↗
PubMed2005

Pesticide extraction efficiency of two solid phase disk types after shipping.

An interlaboratory study was conducted to compare pesticide recovery from Empore C(18) and Speedisks C(18)XF solid phase extraction disks after shipping. Four pesticides were used for the comparison of the two disk extraction materials: atrazine, diazinon, metolachlor, and tebuconazole. These pesticides were chosen to provide a range of physiochemical properties. Water samples were extracted onto the disk types and shipped to a cooperating laboratory for elution and analysis. The mean recoveries from Empore disks were atrazine, 95%; diazinon, 91%; metolachlor, 92%; and tebuconazole, 83%. The recoveries from Speedisks C(18)XF were atrazine, 89%; diazinon, 87%; metolachlor, 86%; and tebuconazole, 79%. Means for each of the pesticides using the different disk types were not statistically different (alpha = 0.05), but results were more variable when using Speedisks C(18)XF as compared to Empore disks. Reasons for the increased variability are discussed, but overall results indicate that Speedisks C(18)XF could be used as an alternative to Empore disks. Speedisks C(18)XF are enclosed in a plastic housing, so they can be used more easily in remote sampling sites without the possibility of glassware breakage, no prefiltration of samples is needed, and there are realignment problems that can be associated with the Empore disks.

Acetamides↗
PubMed2005

Determination of pesticides and PCBs in virgin olive oil by multicolumn solid-phase extraction cleanup followed by GC-NPD/ECD and confirmation by ion-trap GC-MS.

A multicolumn solid-phase extraction cleanup for the determination of organophosphorus (OP) and organochlorine (OC) pesticides plus PCB congeners in virgin olive oil is presented. The method involves dissolution of the olive oil in hexane, followed by a cleanup system using a diatomaceous earth column (Extrelut-QE) with reversed (C(18)) and normal (alumina) phase SPE columns. Determination of OPs was by GC-NPD, while the OCs and PCBs were analyzed using GC-ECD. Recovery assays for OPs varied from 81.7% to 105.3%, for OCs ranged between 74.3% and 99.4%, while for PCBs were from 60.1% to 119.2%. Quantitation limits ranged from 10 to 25 microg/kg olive oil for OPs, and from 1 to 6 microg/kg olive oil for OCs and PCBs. In the case of positive samples, the confirmation of pesticide identity was performed by ion-trap GC-MS/MS. The applicability of the method was assayed with 19 virgin olive oil samples collected from different olive mills of Aragón (Spain). Only one OP pesticide (acephate) was detected in one sample at a concentration of 10 microg/kg. Organochlorine pesticides were found in 5-47% of samples at very low levels ranging from 1.5 to 5.2 microg/kg. PCBs were found in 20-90% of samples, showing concentrations between 2.3 and 17.3 microg/kg.

Chromatography, Gas↗
PubMed2005

Multiresidue analysis of pesticides in soil by gas chromatography with nitrogen-phosphorus detection and gas chromatography mass spectrometry.

A rapid multiresidue method for the simultaneous determination of 25 fungicides and insecticides in soil was developed. Soil samples are extracted by sonication with a water-acetonitrile mixture, and the pesticides are partitioned into dichloromethane. Final determination was made by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). Confirmation analysis of pesticides was carried out by GC-MS in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. The average recovery by the GC-NPD method obtained for these compounds varied from 68.5% to 112.1% with a relative standard deviation between 1.8% and 6.2%. The GC-NPD method presents good linearity over the range assayed 50-2000 microg/L, and the detection limit for the pesticides studied varied from 0.1 to 10.4 microg/kg. The proposed method was used to determine pesticide levels in soil samples from experimental greenhouse pepper cultivation.

Chromatography, Gas↗
PubMed2006

Sample extraction method combining micellar extraction-SPME and HPLC for the determination of organochlorine pesticides in agricultural soils.

A method for the determination of organochlorine pesticides in soil samples combining microwave assisted micellar extraction (MAME) with solid-phase microextraction (SPME) and high-performance liquid chromatography-UV has been developed. A mixture of two nonionic surfactants (polyoxyethylene 10 lauryl ether and polyoxyethylene 10 stearyl ether) was used for the extraction of pesticides from agricultural soils, and different types of SPME fibers were compared. The different parameters which affect extraction efficiency in the SPME procedure were optimized such as extraction time and temperature. The method developed involves extraction and preconcentration for the target analytes in soil samples. The analytical parameters were also studied and good recoveries obtained, RSD being lower than 10% and detection limits ranging between 36 and 164 ng g(-1) for the pesticides studied. The proposed method was successfully applied to the determination of some organochlorine pesticides in several kinds of agricultural soil samples with different characteristics.

Agriculture↗
PubMed2006

Soil microbial activity is affected by Roundup WeatherMax and pesticides applied to cotton (Gossypium hirsutum).

Adoption of glyphosate-based weed control systems has led to increased use of the herbicide with continued use of additional pesticides. Combinations of pesticides may affect soil microbial activity differently than pesticides applied alone. Research was conducted to evaluate the influence of glyphosate-based cotton pest management systems on soil microbial activity. Soil was treated with commercial formulations of trifluralin, aldicarb, and mefenoxam + pentachloronitrobenzene (PCNB) with or without glyphosate (applied as Roundup WeatherMax). The soil microbial activity was measured by quantifying C and N mineralization. Soil microbial biomass was determined using the chloroform fumigation-incubation method. Soils treated with glyphosate alone exhibited greater cumulative C mineralization 30 days after treatment than all other treatments, which were similar to the untreated control. The addition of Roundup WeatherMax reduced C mineralization in soils treated with fluometuron, aldicarb, or mefenoxam + PCNB formulations. These results indicate that glyphosate-based herbicides alter the soil microbial response to other pesticides.

Biomass↗
PubMed2004

pH-dependence of pesticide adsorption by wheat-residue-derived black carbon.

The potential of black carbon as an adsorbent for pesticides in soils may be strongly influenced by the properties of the adsorbent and pesticides and by the environmental conditions. This study evaluated the effect of pH on the adsorption of diuron, bromoxynil, and ametryne by a wheat (Triticum aestivum L.) residue derived black carbon (WC) as compared to a commercial activated carbon (AC). The pH drift method indicated that WC had a point of zero charge of 4.2, much lower than that of 7.8 for AC. The density of oxygen-containing surface functional groups, measured by the Boehm titration, on WC was 5.4 times higher than that on AC, resulting in a pesticide adsorption by WC being 30-50% of that by AC, due to the blockage of WC surface by the waters associated with the functional groups. A small decrease (5.5%/unit pH) in diuron adsorption by WC with increase in pH resulted from increased deprotonation of surface functional groups at higher pH values. A much larger decrease (14-21%/unit pH) in bromoxynil adsorption by WC with increase in pH resulted from the deprotonation of both the adsorbate and surface functional groups of the adsorbent. The deprotonation reduced the adsorptive interaction between bromoxynil and the neutral carbon surface and increased the electrical repulsion between the negatively charged WC surface and bromoxynil anions. Deprotonation of ametryne with increase in pH over the low pH range increased its fraction of molecular form and thus adsorption on WC by 15%/unit pH. Further increase in pH resulted in a 20%/unit pH decrease in ametryne adsorption by WC due primarily to the development of a negative charge on the surface of WC. The pH-dependent adsorption of pesticides by black carbon may significantly influence their environmental fate in soils.

Adsorption↗
PubMed1997

Effect of spraying selected pesticides on the contents of specified minerals in cabbage.

The present study was conducted to assess the effect of spraying of pesticides on the content of minerals in cabbage harvested at varying waiting periods (0, 7, 14 and 21 days) after spraying. The amounts of phosphorus and zinc in cabbage were significantly (p < 0.05) decreased while those of iron, calcium and potassium were significantly (p < 0.05) increased by the sprayings of pesticides. At varying waiting periods after the spraying of pesticides calcium, phosphorus, zinc and potassium contents of cabbage were found to be decreased remarkably (p < 0.05) while the content of iron was increased significantly (p < 0.05). Between the two pesticides, the spraying of endosulfan exerted a more pronounced effect in altering the contents of minerals than the spraying of malathion.

Brassica↗