Analytical and kinetic study of the aqueous hydrolysis of four organophosphorus and two carbamate pesticides

The hydrolysis of six selected pesticides has been studied in aqueous solution. Four organophosphorus pesticides (disulfoton, isofenfos, isazofos and profenfos) and two N-methylcarbamate derivatives (oxamyl and ethiofencarb) were selected. Hydrolysis was performed in purified buffered water at different pH in the range 7.0–10.0 (ionic strength?=?2.5?mM, T?=?25°C). At pH?=?8.0, isofenfos and disulfoton (t _1/2?≈?4 years, t _1/2?≈?1 year, resp.) were found to be far more stable than isazofos (t _1/2?≈?5 months), ethiofencarb and profenofos (t _1/2<1 month), themselves more stable than oxamyl (t _1/2?≈?1 day). As expected, a strong dependence on pH was observed for all pesticides: the rate of degradation increased when the pH increased. Degradation products were identified by GC–MS and/or LC–MS. Possible structures are presented in the article.     

Stratification and tributyltin variability in San Diego Bay

Tributyltin (TBT), a biocidal antifoulant in many marine paints, was measured in near-surface and near-bottom water over a 25 h period at the entrance to a marina in San Diego Bay, USA. Surface water concentrations varied from 20 to 225 nanograms per liter (ng dm^?3) as TBT chloride and bottom water varied from non-detectable (<1 ng dm^?3) to 77 ng dm^?3. Surface water concentrations varied, with highest concentrations associated with ebbing tides, and lowest concentrations with flooding tides, indicating that the yacht basin is a source of TBT. Bottom water TBT concentrations were almost always lower than corresponding surface water concentrations. The highest bottom water concentrations were associated with flooding tides and lowest surface water TBT concentrations. Physical water column measurements indicate that vertical stratification developed during ebbing tides and dissipated during flooding tides. This accounted for maximum bottom water and minimum surface water TBT concentrations during flooding tides, due, at least in part, to vertical mixing and dilution during flood tides.     

GC/MS studies on revealing products and reaction mechanism of photodegradation of pesticides

The photolytic degradation of frequently applied s-triazine type pesticides was investigated. A special, immersible UV-light source was applied in order to carry out photodegradation. The degradation processes were followed by TLC, GC and GC/MS techniques. Following the irradiation of the sample, the degradation products were isolated by SPE column chromatography. EI mass spectrometry was used to identify the degradation species.All four of the different s-triazine type pesticides studied underwent photolytic decomposition. The kinetic aspect of photodegradation of prometryn, terbutryn, simazine and atrazine was revealed completely, while in case of prometryn and terbutryn a detailed mechanism of photolytic transformation was established. Four degradation species were detected, as a consequence of two parallel ways of degradation. Both pesticides suffered the loss of thio-methyl groups prior to cleavage of the alkyl groups. Deamination did not occur under the conditions applied. The kinetic behaviour with respect to photodegradation displayed significant differences when comparing the decomposition of s-triazine type pesticides: prometryn decomposed 10 times faster than terbutryn.     

Development of a procedure for the multiresidue analysis of pesticides in vineyard soils and its application to real samples

A procedure for multiresidue analysis was developed for the extraction and determination of 17 pesticides, including herbicides, fungicides, and insecticides, as well as certain degradation products, in vineyard soils from La Rioja region (Spain). Different solvents and mixtures were tested in spiked pesticide‐free soils, and pesticides were comparatively evaluated by gas chromatography with mass spectrometry and liquid chromatography with mass spectrometry. Recoveries >70%, with relative standard deviations <9%, were obtained when a mixture of methanol/acetone or a mixture of methanol/CaCl₂ 0.01 M for the most polar compounds was selected as the extraction solvent. Method validation was accomplished with acceptable linearity (r² ≥ 0.987) within the concentration range of 0.005–1 μg/mL corresponding to 1.667–333.4 μg/kg and 0.835–167.1 μg/kg for liquid chromatography with mass spectrometry and gas chromatography with mass spectrometry, respectively, and detection limits <0.4 μg/kg for the compounds were studied. The extraction method was applied to 17 real vineyard soil samples, and terbuthylazine and its metabolite desethylterbuthylazine were the most ubiquitous compounds, as they were detected in the 100% of the soils analyzed. The presence of fungicides was also high, and the presence of insecticides was lower than other pesticides. The results confirm the usefulness of the optimized procedure for monitoring residues in vineyard soils.     

Multi-residue screening of pesticides in vegetables,fruits and baby food by stir bar sorptive extraction-thermal desorption-capillary gas chromatography-mass spectrometry

The performance of stir bar sorptive extraction (SBSE) for the enrichment of pesticides from vegetables, fruits and baby food samples is discussed. After extraction with methanol, an aliquot is diluted with water and SBSE is performed for 60 min. By applying a new thermal desorption unit (TDU), fully automated and unattended desorption of 98 stir bars is feasible, making SBSE very cost-effective. The presence of pesticide residues is elucidated with the retention time locked gas chromatography–mass spectroscopy method (RTL-capillary GC–MS). With SBSE–RTL-capillary GC–MS operated in the scan mode, more than 300 pesticides can be monitored in vegetables, fruits and baby food. The multi-residue method (MRM) described provides detectabilities from the mg/kg (ppm) to the sub-μg/kg (ppb) level, thereby complying with the maximum residue levels (MRLs) set by regulatory organizations for pesticides in different matrices. Several examples, i.e. pesticide residues in lettuce, pears, grapes and baby food, illustrate the potential of SBSE–RTL-capillary GC–MS.     

Organic complexation and total dissolved trace metal analysis in estuarine waters: comparison of solvent-extraction graphite furnace atomic absorption spectrometric and chelating resin flow injection inductively coupled plasma-mass spectrometric analysis

The measured concentrations of cadmium, cobalt, copper, nickel, lead, zinc, and manganese in acidified (pH<2) estuarine water samples analyzed for total dissolved trace metal concentrations using on-line chelating resin column partitioning with inductively coupled plasma-mass spectrometry (CRCP-ICP-MS) were compared to those analyzed by graphite furnace atomic absorption spectrometry (GFAAS) after liquid-liquid extraction using a combination of 1-pyrrolidinedithiocarbamate/diethyldithiocarbamate (PDC/DDC). Although there was good agreement between the two sets of analyses for cadmium, lead, manganese, and zinc concentrations, those of cobalt, copper, and nickel determined by CRCP-ICP-MS were found to be 10-20% lower than those determined by solvent-extraction GFAAS. The different yields were positively correlated (R>0.961, simple linear regression) to the dissolved organic carbon (DOC) concentration of the samples. Good agreement between the two methods for cobalt and copper was achieved after ultraviolet (UV) digestion of the acidified samples. Samples collected from the South Bay of the San Francisco Estuary with high DOC showed the greatest difference for cobalt, copper, and nickel which is tentatively attributed to complexation with humic material for copper and cobalt and strong synthetic chelating agents such as ethylenediaminetetraacetic acid (EDTA) for nickel. This is consistent with previous studies on copper, nickel and cobalt complexation in this region. We recommend UV digestion of acidified estuarine samples prior to multi-element analysis by chelating resin flow injection ICP-MS methods.     

Levels and patterns of polychlorinated biphenyls in water collected from the San Francisco Bay and Estuary, 1993–95

Levels of polychlorinated biphenyls (PCBs) were measured in water (particulate and dissolved fractions) from various locations in the San Francisco Estuary over the years 1993–1995 during six cruises. Geometric mean levels of ΣPCBs (sum of 58 congeners) in the combined dissolved and particulate fractions for the six cruises ranged from 340?ng/L to 1600?ng/L. Comparing this data to previous data from 1975 and 1980 does not reveal any significant temporal trends. The partitioning of PCBs into the dissolved/particulate fraction were correlated with total suspended solids. Using the novel chemometric technique of polytopic vector analysis (PVA) on the data from cruise 8 (April 1995), five separate PCB congener fingerprints were identified in the data. Fingerprint 1 (or end-member 1) represents a slightly degraded source of Aroclor^® 1260 in the northern part of the South Bay; the end-member (EM) 2 fingerprint is related to a predominantly Aroclor^® 1260 source that has been moderately-severely degraded present in the highest proportions in the Pacific Ocean sample; EM-3 is interpreted as a slightly degraded Aroclor^® 1242:1254:1260 mixture in southern San Pablo Bay; end-member 4 is interpreted as a moderately degraded source of multiple Aroclors^® and is present in the river samples; EM-5 is interpreted as a slightly degraded Aroclor^® 1254/1260 mixture present in northern San Pablo Bay and the South Bay.     

Levels and patterns of polychlorinated biphenyls in water collected from the San Francisco Bay and Estuary, 1993–95

Levels of polychlorinated biphenyls (PCBs) were measured in water (particulate and dissolved fractions) from various locations in the San Francisco Estuary over the years 1993–1995 during six cruises. Geometric mean levels of ΣPCBs (sum of 58 congeners) in the combined dissolved and particulate fractions for the six cruises ranged from 340 ng/L to 1600 ng/L. Comparing this data to previous data from 1975 and 1980 does not reveal any significant temporal trends. The partitioning of PCBs into the dissolved/particulate fraction were correlated with total suspended solids. Using the novel chemometric technique of polytopic vector analysis (PVA) on the data from cruise 8 (April 1995), five separate PCB congener fingerprints were identified in the data. Fingerprint 1 (or end-member 1) represents a slightly degraded source of Aroclor^? 1260 in the northern part of the South Bay; the end-member (EM) 2 fingerprint is related to a predominantly Aroclor^? 1260 source that has been moderately-severely degraded present in the highest proportions in the Pacific Ocean sample; EM-3 is interpreted as a slightly degraded Aroclor^? 1242:1254:1260 mixture in southern San Pablo Bay; end-member 4 is interpreted as a moderately degraded source of multiple Aroclors^? and is present in the river samples; EM-5 is interpreted as a slightly degraded Aroclor^? 1254/1260 mixture present in northern San Pablo Bay and the South Bay. Received: 21 March 1997 / Revised: 23 May 1997 / Accepted: 28 May 1997     

The use of Nafion-coated thin mercury film electrodes for the determination of the dissolved copper speciation in estuarine water

Differential pulse anodic stripping voltammetry (DPASV) using a Nafion-coated thin mercury film electrode (NCTMFE) was implemented to determine the dissolved copper speciation in saline estuarine waters containing high concentrations of dissolved organic matter (DOM). The study used model ligands and estuarine water from San Francisco Bay, California, USA to demonstrate that the NCTMFE is more effective at distinguishing between electrochemically inert and labile copper species when compared to the conventional thin mercury film electrode (TMFE). Copper titration results verify that the NCTMFE better deals with high concentrations of DOM by creating a size-exclusion barrier that prevents DOM from interacting with the mercury electrode when performing copper speciation measurements. Pseudovoltammograms were used to illustrate that copper complexes found in natural waters were more apt to be electrochemically inert at the NCTMFE relative to the TMFE when subjected to high negative overpotentials. Copper speciation results using the NCTMFE from samples collected in San Francisco Bay estimated that >99.9% of all copper was bound to strong copper-binding ligands. These L₁-class ligands exceeded the concentration of total dissolved copper in all samples tested and control the equilibrium of ambient [Cu²⁺] in the San Francisco Bay estuary.     

Certification of SRM 1589a PCBs,pesticides, PBDEs,and dioxins/furans in human serum

The Certificate of Analysis for SRM 1589a PCBs, Pesticides, PBDEs, and Dioxins/Furans in Human Serum has been updated to include certified concentration values for 27 polychlorinated biphenyl (PCB) congeners, three chlorinated pesticides, and four polybrominated diphenyl ether (PBDE) congeners as well as reference concentration values for 27 additional PCB congeners, six additional chlorinated pesticides, three additional PBDE congeners, and selected polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). This represents an addition of concentration values for 29 PCB congeners and for PBDE congeners that were not quantified in the previous issue of SRM 1589a. With the increased number of certified and reference concentration values for PCBs and the inclusion of certified and reference concentration values for PBDEs, this serum material will be more useful as a reference material for contaminant monitoring in human tissues and fluids. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Sampling and analysis of pesticides in ambient air

Developments in the sampling and determination of pesticides in ambient air have been discussed and data on the occurrence of pesticides in atmosphere have been presented. Developments in active sampling methods were reviewed and the different materials used for trapping pesticides from gas and particulate phases were discussed. Likewise, the use and developments of passive air samplers were reviewed. This article pays special attention to the analysis of pesticides trapped from ambient air, and recapitulate the procedures for extraction, clean-up and determination of these substances. Improvements in sampling procedures, analytical methods and monitoring activities are necessary to advance the knowledge of occurrence of currently used pesticides in atmosphere and their impact over environment and humans.     

Supercritical fluid extraction and clean-up of organochlorine pesticides and polychlorinated biphenyls in mussels

The simultaneous extraction and clean-up of mussel samples followed by gas chromatography with electron-capture detection and mass spectrometric confirmation of 15 organochlorine pesticides (OCPs) and 11 polychlorinated biphenyls (PCBs) is developed using Florisil sorbent in the supercritical fluid extraction cell. The method detection limits vary from 1 to 10 ng/g for OCPs and from 2 to 15 ng/g for PCBs. Mean reproducibilities of 11% and 10% and mean recoveries of 80% and 53%, respectively, for OCPs and PCBs are obtained. The feasibility of the proposed supercritical fluid extraction method was confirmed by analyzing a certified reference material and mussels collected from Taiwan region. The method is simple, rapid and requires only small amounts of samples and solvents. It may serve as a screening protocol for the determination of OCPs and PCBs in mussels on a routine basis.     

Analyses of pesticides and their metabolites in foods and drinks

The importance of matrix pretreatment, sample extraction and clean-up in multiresidue methods for pesticide analyses is discussed, with emphasis on alternative new techniques attempted worldwide such as accelerated solvent extraction, microwave-assisted extraction, solid-phase extraction, solid-phase micro-extraction, matrix solid-phase dispersion, supercritical fluid chromatography, ultrasonic extraction and gel permeation chromatography. Detection employing capillary gas chromatography and high-performance liquid chromatography in conjunction with mass spectrometry, capillary electrophoresis, immunoassay techniques and others is summarized.     

Electroanalytical methods based on bimetallic nanomaterials for determination of pesticides: Past,present, and future

The excessive use of pesticides in agricultural or non-agricultural fields causes the emergence of environmental and human health problems. Therefore, there is a need to develop simple, fast, sensitive, selective, and low-cost methods for analyzing pesticides from different matrices. Although many analysis methods have been developed to determine pesticides, nanomaterial-based electroanalytical methods offer numerous advantages such as rapid and low cost of analysis, low sample volume requirement, field deployability, and miniaturization to improve the performance of the developed methods. Among different nanomaterials, bimetallic nanomaterials such as gold, platinum, palladium, nickel, and iron-based nanomaterials in combination with other metals have been extensively used as electrode modification agents due to their electrocatalytic characteristics and the synergistic effect of two metals. In this review, firstly, the basic information of pesticides and bimetallic nanomaterials was summarized. Properties, synthesize, and architectures of bimetallic nanomaterials and their nanocomposites were explained in detail. Current applications and utilization of bimetallic nanomaterials for pesticides detection were reviewed by selected studies with working range, the limit of detection, sensitivity, analytical application, and some experimental conditions. In conclusion, the current challenges and future trends for analyzing pesticides based on electroanalytical methods combined with bimetallic nanomaterials were highlighted.     

Development, validation and application of a method based on DI-SPME and GC-MS for determination of pesticides of different chemical groups in surface and groundwater samples

A simple and rapid method based on solid-phase micro extraction (SPME) technique followed by gas chromatography-mass spectrometry with selected ion monitoring (GC-MS, SIM) was developed by the simultaneous determination of 16 pesticides of seven different chemical groups [Six organophosphorus (trichlorfon, diazinon, methyl parathion, malathion, fenthion and ethyon), three pyrethroids (bifenhin, permethrin, cypermethrin), two imidazoles (imazalil and prochloraz), two strobilurins (azoxystrobin and pyraclostrobin), one carbamate (carbofuran), one tetrazine (clofentezine), and one triazole (difenoconazole)] in water. The pesticides extraction was done with direct immersion mode (DI-SPME) of the polyacrilate fiber (PA 85 µm). The extraction temperature was adjusted to 50 °C during 30 min, while stirring at 250 rpm was applied. After extraction, the fiber was introduced in the GC injector for thermal desorption for 5 min. at 280 °C. The method was validated using ultra pure water samples fortified with pesticides at different concentration levels and shows good linearity in the concentrations between 0.05 and 250.00 ng mL^− 1. The LOD and LOQ ranged, from 0.02 to 0.30 ng mL^− 1 and 0.05 to 1.00 ng mL^− 1, respectively. Intra-day and inter-day precisions were determined in two concentration levels (5.00 and 50.00 ng mL^− 1). Intra-day relative standard deviation (%R.S.D.) ranged between 3.6 and 13.6%, and inter-day (%R.S.D.) ranged between 6.3 and 18.5%. Relative recovery tests were carried out spiking the ultra pure sample with standards in three different concentration levels 0.20, 5.00 and 50.00 ng mL^− 1. The recovery at 0.20 ng mL^− 1 level varied from 86.4 ± 9.4% to 108.5 ± 10.5%, at 5.00 ng mL^− 1 level varied from 77.5 ± 10.8% to 104.6 ± 9.6% and at 50.00 ng mL^− 1 level varied from 70.2 ± 4.6% to 98.4 ± 8.5%. The proposed SPME method was applied in twenty-six water samples collected in the “Platô de Neópolis”, State of Sergipe, Brazil. Methyl parathion was detected in five samples with an average concentration of 0.17 ng mL^− 1 and bifenthrin, pyraclostrobin and azoxystrobin residues were found in three samples with average concentrations of 2.28, 3.12 and 0.15 ng mL^− 1, respectively.     

Confirmation of chlorotriazine pesticides,their degradation products and organophosphorus pesticides in soil samples using gas chromatography-mass spectrometry with electron impact and positive- and negative-ion chemical ionization

Gas chromatography-mass spectrometry (GC-MS) with electron impact (EI), positive-ion chemical ionization (PCI) and negative-ion chemical ionization (NCI) were applied as confirmatory techniques for residue analysis of chlorotriazine pesticides, their degradation products and organophosphorus pesticides in soil samples. Clean-up was effected using a Florisil column with subsequent analysis by GC with a nitrogen-phosphorus detector. GC-MS with the EI mode of operation is the common mode of confirmation for all the pesticides. Further confirmation by either GC-MS with PCI and NCI for chlorotriazines and organophosphorus pesticides, respectively, is recommended. The method was applied to the determination of residue levels of atrazine, deethylatrazine, deisopropylatrazine, simazine, fenitrothion and tetrachlorvinphos in several soil samples at levels from 5 ng g^?1 to 9 μg g^?1.     

Multianalyte determination of different classes of pesticides (acidic,triazines, phenyl ureas,anilines, organophosphates,molinate and propanil) by liquid chromatography-electrospray-tandem mass spectrometry

This work describes the optimization of a liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS-MS) method for the multianalyte determination of twenty pesticides, selected based on current regulations and extent of use. Chromatographic separation was carried out on a Purospher STAR RP-18e column using gradient acetonitrile-water as mobile phase. Triazines, phenylureas, organophosphates, anilines, and molinate were determined in the positive ionization mode, and acidic pesticides and propanil in the negative ion mode. Two different precursor ion-product ion transitions were selected for each analyte and monitored under time scheduled multiple reaction monitoring (MRM) conditions. The optimized method was shown to be linear in the range 1 to 1000 ng/mL with correlation coefficients higher than 0.99 for all but one (diazinon) of the analytes, very sensitive (with limits of detection between 0.010 and 4.528 ng/mL), and repeatable (with relative standard deviations, calculated from the replicate analysis of standard mixtures, lower than 14%). The present work was also devoted to the elucidation of the structures of the principal fragment ions obtained after collision-induced dissociation of the pesticides investigated, an aspect often overlooked in the literature.     

Simultaneous extraction and determination of various pesticides in environmental waters

A simple and rapid method was developed for the simultaneous analysis of nine different pesticides in water samples by gas chromatography with mass spectrometry. A number of parameters that may affect the recovery of pesticides, such as the type of solid‐phase extraction cartridge, eluting solvent in single or combination and their volumes, and water pH value were investigated. It showed that three solid‐phase extraction cartridges (Strata‐X, Oasis HLB, and ENVI‐18) produced the greatest recovery while ethyl acetate/dichloromethane/acetone (45:10:45, 12 mL) followed by dichloromethane (6 mL) was efficient in eluting target pesticides from solid‐phase extraction cartridges. Different water pH values (4–9) did not show a significant effect on the pesticides recovery. The optimized method was verified by performing spiking experiments with a series of concentrations (0.002–10 μg/L) in waters, with good linearity, recovery, and reproducibility for most compounds. The limit of detection and limit of quantification of this optimized method were 0.01–2.01 and 0.02–6.71 ng/L, respectively, much lower than the European Union environmental quality standard for the pesticides (0.1 μg/L) in waters. The proposed method was further validated by participation in an interlaboratory trial. It was then subsequently applied to river waters from north‐east Scotland, UK, for the determination of the target pesticides.     

Cyclodextrin-enhanced fluorescence and photochemically-induced fluorescence determination of five aromatic pesticides in water

The effect of β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) aqueous solutions upon the fluorescence and photochemically-induced fluorescence (PIF) properties of five pesticides, including coumatetralyl, pirimiphos-methyl, chlorpyriphos, deltamethrin and fenvalerate was investigated. A 1:1 stoichiometry was found for the β-CD and HP-β-CD complexes formed with all compounds. Binding constant values, ranging between about 90 and 830 M⁻¹ were calculated using the iterative nonlinear least-squares regression approach. Cyclodextrin-enhanced fluorescence and PIF methods were developed for the determination of these pesticides with linear dynamic ranges over two orders of magnitude, and limits of detection (LOD) between 0.2 and 54 ng ml⁻¹ according to the compound. Application to the analysis of tap water and river water samples yielded satisfactory recoveries (88–116%). The method seems to be suitable for environmental water analysis.     

Multi-residue analysis of traces of pesticides and antibiotics in honey by HPLC-MS-MS

The aim of this work was to develop an analytical method for simultaneous assay of residues of two families of antibiotics, and three pesticides, in honey. The assays involved a mixture of five tetracyclines, four sulfamides, and the pesticides coumaphos, carbendazim, and amitraz (two metabolites). All the compounds were extracted from honey and pre-concentrated by optimised solid-phase extraction (SPE). Analysis was by high-performance liquid chromatography-mass spectrometry-mass spectrometry (HPLC-MS-MS) using a triple-quadrupole spectrometer in multiple reaction monitoring (MRM) mode in order to identify and quantify the compounds present (Sheth et al J Agric Food Chem 38:1125–1130, 1990). During development of the analytical method a strong matrix effect was found that depended on the floral origin of the honey. This led to the development of a standard additions method to quantify the contaminants sought.