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PubMed1998

Prediction of percutaneous absorption from physicochemical data: a model based on data of in vitro experiments.

Correlations between in vitro percutaneous absorption data and physicochemical properties of industrial chemicals are evaluated in order to develop predictive mathematical models based on said properties. Percutaneous diffusion of 16 pounds of occupational interest, eight of which were polycyclic aromatic hydrocarbons (acenaphthene, anthracene, benzo(a)anthracene, chrysene, phenanthrene, fluorene, naphthalene, pyrene), six organophosphorus insecticides (acephate, chlorpyrifos, dimethoate, fenitrothion, methamidophos, omethoate) and two phenoxycarboxylic herbicides (2,4-D, MCPA), were tested in vitro using monkey (Cercopithecus aetiops) skin. The test apparatus consisted of nine static diffusion cells with normal saline, gentamycin sulphate and 4% bovine serum albumin as receiving solution. Test compounds were applied at various concentrations in 30 microliters of acetone solution and determined, in the receiving phase, by chemical analysis. Values for ln Kow (octanol/water partition coefficient) were correlated with experimentally determined values of the permeability constant Kp (r = 0.90, P < 0.001) and lag time (r = 0.81, P < 0.01). Analysis of variance in a model of multiple linear regression between Kp, ln Kow and water solubility [water] of the compounds, showed that the data had a highly significant fit (P < 0.0001). A more general model which also included molecular weight (MW) and vapour pressure was evaluated as well, but the two variables made no substantial difference. Multiple regression analysis between lag time, ln Kow and [water] was significant (P < 0.0001), whereas introduction of vapour pressure and MW as independent variables did not significantly improve the predictive effect on lag time. Our experimental system, therefore, enables the values of Kp and lag time to be predicted with reasonable precision on the basis of ln Kow and [water] values, using the algorithm derived from the multiple linear regression equation.

Animals↗
PubMed2000

Multiresidue analysis of seventeen pesticides in wine by gas chromatography with mass-selective detection.

We have developed a multiresidue method permitting the simultaneous quantitation of 17 pesticides in wine: dicloran, dimethoate, diazinon, chlorpyrifos-methyl, vinclozolin, carbaryl, methiocarb, dichlofluanid, parathion-ethyl, triadimefon, procymidone, myclobutanil, iprodione, imidan, dicofol, phosalone and azinphos-methyl. Solid-phase extraction of 0.5 ml of wine sample is followed by direct injection of 1 microl of the eluent onto a DB-5 MS gas chromatographic column followed by mass-selective detection using one target and two qualifier ions for each pesticide. The extraction and injection steps are carried out with automatic instrumentation. Good resolution of all compounds was achieved with a run-time approximating 23 min. Detection and quantitation limits were around 2 microg/l and 10 microg/l, respectively, with linear calibration curves up to 3 mg/l for most constituents. Recovery in half the compounds was >90%, and >80% in most of the remainder. Imprecision (relative standard deviation) was <10% for most pesticides and <18% in all. Further analytes can be added to the repertoire without difficulty. The method merits consideration together with four other multiresidue methods now available that offer similar analytical characteristics, slower run-times, and a different selection of analytes.

Gas Chromatography-Mass Spectrometry↗
PubMed1977

Detection and determination of organophosphorus insecticides in tissues by thin-layer chromatography.

The toxicological analysis of 12 common organophosphorus insecticides is described. Suitable methods for the extraction of organophosphorus insecticides from tissues are proposed. The detection, identification and estimation of these insecticides by thin-layer chromatography is described for 25 solvent systems and a series of chromogenic reagents. The distribution of insecticides in human body tissues in five cases of poisoning by ethyl parathion, malathion, dimethoate, sumithion and phosphamidon has also been studied.

Autopsy↗
PubMed2001

Optimization and evaluation of low-pressure gas chromatography-mass spectrometry for the fast analysis of multiple pesticide residues in a food commodity.

A fast method of analysis for 20 representative pesticides was developed using low-pressure gas chromatography-mass spectrometry (LP-GC-MS). No special techniques for injection or detection with a common quadrupole GC-MS instrument were required to use this approach. The LP-GC-MS approach used an analytical column of 10 m x 0.53 mm I.D., 1 microm film thickness coupled with a 3 m x 0.15 mm I.D. restriction capillary at the inlet end. Thus, the conditions at the injector were similar to conventional GC methods, but sub-atmospheric pressure conditions occurred throughout the analytical column (MS provided the vacuum source). Optimal LP-GC-MS conditions were determined which achieved the fastest separation with the highest signal/noise ratio in MS detection (selected ion monitoring mode). Due to faster flow-rate, thicker film, and low pressure in the analytical column, this distinctive approach provided several benefits in the analysis of the representative pesticides versus a conventional GC-MS method, which included: (i) threefold gain in the speed of chromatographic analysis; (ii) substantially increased injection volume capacity in toluene; (iii) heightened peaks with 2 s peak widths for normal MS operation; (iv) reduced thermal degradation of thermally labile analytes, such as carbamates; and (v) due to larger sample loadability lower detection limits for compounds not limited by matrix interferences. The optimized LP-GC-MS conditions were evaluated in ruggedness testing experiments involving repetitive analyses of the 20 diverse pesticides fortified in a representative food extract (carrot), and the results were compared with the conventional GC-MS approach. The matrix interferences for the quantitation ions were worse for a few pesticides (acephate, methiocarb, dimethoate, and thiabendazole) in LP-GC-MS, but similar or better results were achieved for the 16 other analytes, and sample throughput was more than doubled with the approach.

Food Contamination↗
PubMed1991

Determination of triazines and organophosphorus pesticides in water samples using solid-phase extraction.

Octadecyl (C18)-bonded porous silica was evaluated for the extraction of triazine and organophosphorus pesticides from natural water. The extraction results showed an effective performance when 11 of water was passed through small glass columns containing 500 mg of 50-100-microns C18 bonded porous silica. The adsorbed compounds were removed with ethyl acetate, evaporated to 200 microliters and determined by gas chromatography. The overall average recoveries were greater than 85% except for dimethoate and trichlorfon. Application of this procedure to the analysis of natural water samples gave results that agree well with those obtained by solvent extraction methods.

Chromatography, Gas↗
PubMed2003

Screening and determination of pesticides in soil using continuous subcritical water extraction and gas chromatography-mass spectrometry.

In the present work the efficiency of water under subcritical conditions for the extraction of pesticides having a broad spectrum of polarities from soils was evaluated. The pesticides under study were carbofuran, hexachlorobenzene, dimethoate, simazine, atrazine, lindane, diazinon, methylparathion, alachlor, aldrin-R, metholachlor, chlorpyrifos, heptachlor epoxide, dieldrin, endrin, 4,4-DDT and metoxichlor. Optimization studies were carried out using a blank soil (Non-Polluted Soil 1, CLN-1, RTC) and a real soil which were previously spiked with the pesticide mixture and aged for 60 days. A laboratory-made aluminum oven with controlled temperature was used to carry out the leaching process with subcritical water, where it is placed a pre-heater and the extraction cell. The following variables were studied, keeping the pressure controlled about 1200 p.s.i.: the extraction temperature, the time of static and dynamic extraction and the flow-rate of water (1 p.s.i. = 6894.76 Pa). The extraction efficiency of the pesticides increases with the temperature trending to the quantitative extraction at temperatures near to 300 degrees C. After the extraction process, the analytes were transferred quantitatively to 5 ml dichloromethane, before the determination by GC-MS. The results indicate that under the optimized conditions mostly of the analytes are extracted quantitatively in 90 min with recoveries quite similar to those obtained by the standard Soxhlet extraction procedure. Alternatively, by using an extraction time of 25 min, the method can be used as screening for all the pesticides, with recoveries depending on their polarity.

Gas Chromatography-Mass Spectrometry↗
PubMed2000

Analysis of pesticide residues in matrices with high lipid contents by membrane separation coupled on-line to a high-performance liquid chromatography system.

Separation through membranes coupled to an HPLC system was used as a technique for the analysis of pesticide multiresidues in samples with high lipid contents. As well as the usual procedure, in the proposed system it is possible to recirculate the sample through the membrane cell, which permits the extraction system to be applied to cases in which only a very small volume of sample is available. A procedure for pesticide multiresidue analysis in egg samples was developed as a representative example of the applicability of the proposed method. To accomplish this, the analytes (dichlorvos, dimethoate, propoxur, paraoxon, pirimicarb, atrazine, ametryne, terbutryne, azinphos-methyl, folpet) were subjected to prior extraction in a Soxhlet system, after which the extract was introduced into the membrane separation device coupled to the HPLC system. This procedure afforded clean chromatograms, hence considerably facilitating determination, and at the same time was efficient in removing macromolecular compounds. For egg samples, spiked at a concentration level of 0.750 mg/kg, recoveries ranged from 60 to 98%. The detection limits varied from 0.018 mg/kg for dichlorvos to 0.002 mg/kg for atrazine.

Chromatography, High Pressure Liquid↗
PubMed2002

Determination and load of organophosphorus and organochlorine pesticides at water from Jiulong River Estuary, China.

Seventeen organic phosphorus pesticides (OPs) and 18 organic chlorine pesticides (OCs) at water from Jiulong River Estuary (JLRE) are determined by SPE-GC-(FPD and microECD). The contents of the total OPs (17) ranged from 134.8 to 354.6 ng/l (the mean is 227.2 ng/l). Total OCs concentrations varied from 115.4 to 414.7 ng/l in water (mean 237.7 ng/l). The levels of total hexachlorocyclohexane in water varied from 31.95 to 129.8 ng/l (mean 62.51 ng/l), and those of total DDTs were in the range 19.24-96.64 ng/l (mean 48.69 ng/l). The distribution and behavior characteristics of OPs indicate that five main OPs (methamidophos, dichlorvos, malathion, omethoate and dimethoate) occupied the most part of the total OPs, in addition, the sources of the OPs (mainly from current usage) are not stable. While the OCs mainly came from early application and were more stable. The OPs did not have obvious correlation with the dissoved organic carbon and suspended particulate matter at water from JLRE. It maybe due to the complicated hydrological kinetics in the estuary, and the higher water solubility and weak absorption (with organic matter) action of OPs. When compared with other areas, the OPs and OCs level in JLRE are some moderate.

Absorption↗
PubMed1999

Groundwater contamination by azinphos methyl in the northern Patagonic Region (Argentina).

Approximately 30 groundwater monitoring wells, under a fruit production field, in the Valley of the Neuquen River (Northern Patagonic, Argentina), to which different pesticides have been applied, were sampled eleven times between October 1995 and March 1997. Azinphos methyl was the main pesticide applied and it was detected with the highest frequency in groundwater wells during the period of intensive pesticide application in the Southern Hemisphere. Dimethoate, methidathion, fosmet, cipermethrin, carbaryl, propoxur, carbofuran, benomyl and carbendazim were also detected with lower frequency. The characteristic of the area under study was alkaline soil, with an organic matter content below 2.5% and texture sandy clay loam. The half life of azinphos methyl in soils was 166.2 days in the sun light for horizon A and 194.15 in the dark for horizon B. Leaching of azinphos methyl through the different soil horizons was minimum. On the basis of our lysimeter laboratory data, in which most of the pesticide was adsorbed into the soil column and only small quantities leachate, we inferred that the impact of azinphos methyl on groundwater would be minimal. However, field data indicates that there is a persistence of azinphos methyl in groundwater during the application season.

Argentina↗
PubMed2003

Effects of different plant protection programs on soil microbes.

The aim of this study was to assess the effects of two pesticide regimens (conventional full insurance compared with supervised and reduced pesticide use) and two cultivation techniques (conventional tillage and fertilization compared with no tillage and lower fertilization) on soil microbes in a field study, and to evaluate the results with laboratory tests. The herbicides used were chlorsulfuron, MCPA, and bentazone; the fungicides carboxin-imazalin and propiconazole; and the insecticides dimethoate and pirimicarb. In the field studies, the effects on microbial biota were assessed by measuring biomass (ATP content) and microbial activities related to carbon and nitrogen metabolism (soil respiration, nitrification potential). Potential harmful effects of commercial formulations of the same pesticides on microbes were studied in the laboratory with two bacterial toxicity tests (Pseudomonas putida growth inhibition and Vibrio fischeri luminescence inhibition tests) and with a soil respiration inhibition test. Bioavailability of the pesticides in the soil was assessed by a solid-phase modification of the luminescent bacteria test. In the field studies the microbial activities and biomass followed the weather conditions during the growing season, and significant effects of pesticide treatments on microbial processes were not observed. In the laboratory studies the toxicity of certain pesticides was clearly detected by bacterial toxicity tests. However, in the soil respiration inhibition assessment with soil similar to that used in the field trial, inhibition was observed only at unrealistically high concentrations. This could be due to the limited bioavailability of the pesticides in soil of high clay and organic carbon content.

Adenosine Triphosphate↗
PubMed1996

Genotoxicity of the Ganges water at Narora (U.P.), India.

Water samples were collected from the river Ganga at Narora (U.P.). High performance liquid chromatography analysis of water samples by the liquid extraction procedure indicated the presence of several pesticides such as DDT, alpha-BHC, aldrin, endrin and dieldrin at concentrations of 1.36, 1.38, 0.95, 0.61 and 0.41 ppb, respectively. The organophosphorus pesticides such as dimethoate and methyl parathion also appear to be present at concentrations of 0.20 and 0.41 ppb, respectively. The XAD water concentrates and liquid-liquid extracted water samples were assayed for mutagenic potential by the Ames Salmonella/microsome test. The test samples exhibited a significant degree of mutagenicity with TA102, TA100 and TA98 strains both in the presence and absence of DNA repair defective mutants, recA, lexA and polA of E. coli was observed as compared to their wild-type counterpart in the presence of XAD water concentrates.

Cell Division↗
PubMed2000

Monitoring of the pesticide levels in some water supplies and agricultural land, in El-Haram, Giza (A.R.E.).

Monitoring of pesticide residues were conducted at different locations in the El-Haram region Giza, Egypt. The water samples were collected from El-Haram Giza, canal water supplies (El-Zomor, Abd-el-aal land and seaside and El-Mansorya), in addition to El-Moheet drainage water. The soil samples were collected from the arable land that surrounds water canals. Water samples were obtained by solid phase extraction (SPE) and soil samples by gel permeation chromatography (GPC). The combination of gas chromatography and mass spectroscopy with different ionization techniques was used for determination and identification of the pesticides, which were quantitatively determined as 1 microgram 1(-1) levels in environmental samples. The residues of pesticides were varied between different locations. Also, organochlorine pesticide residues in El-Moheet drainage water were relatively higher than in the canal water. The concentrations of organophosphorous compounds (chlorpyrifos, dimethoate and parathion) seem to be low in water as compared to soil samples. Most findings were less than 1 microgram g(-1), which is considered a low-level finding. Sixteen organochlorine pesticides were detected in most of the water samples and the percent of positive samples followed the order drins > total BHC > total DDT > endosulfan > heptachlor epoxid > heptachlor. Pentachlorophenol (PCP) was detected only in El-Zomor and Abd-el-aal canal water. Results obtained confirm the presence of different pesticide residues representing different chemical classes in the canal waters. This means that the discharging of wastes in to the water supplies must be controlled. Drainage water was highly polluted and contains much more pesticide residues than different canal waters.

Agriculture↗
PubMed2001

An analytical method for the rapid screening of organophosphate pesticides in human biological samples and foodstuffs.

Gas chromatography with nitrogen/phosphorus sensitive detection (GC/PND) and electron impact mass spectrometry (GC/MS) with selected ion monitoring provides a simple, rapid and sensitive method for the determination of organophosphate pesticides (OPs). A selective single-step extraction of 23 different OPs in urine, blood, serum and food samples (baby food, soft drinks and instant soups suspected of contamination from a blackmailing scare) is described. The OPs were extracted with 1ml toluene (with and without addition of mevinphos as internal standard), using a 0.7ml aliquot of urine, blood or serum sample. Food samples (0.2g) were homogenised with water (0.5ml) before extraction. An amount of 1microl of the toluene phase (extraction supernatant) was analysed directly by GC/PND and GC/MS.The method was validated using spiked human serum. The OPs were mixed with serum containing 10mg/ml disodium ethane diamine tetraacetic acid disodium salt (EDTA disodium salt) and stored up to 10 days at 4 and -20 degrees C, respectively. The recovery rates of OPs in freshly spiked human plasma ranged between 50% (dimethoate) and 133% (dialifos). OPs in plasma proved to be stable at -20 degrees C. Their levels decreased only slightly after storage at 4 degrees C.

Animals↗
PubMed1999

Mode of action of pesticides on aflatoxin biosynthesis and oxidase system activity.

The effects of nine pesticides on the biosynthesis of aflatoxin and oxidase activity in wild-type Aspergillus flavus and mutant strains of A. parasiticus avr-1 (w 49) and A. parasiticus ver-1 (wh 1) were investigated. In A. parasiticus, phosphonic acid derivative (lancer) reduced the formation of aflatoxin B2 but B1, G1 and G2 and anthraquinones (versicolorin A, versiconal hemiacetal acetat and averufin) accumulated. Phosphorothioic acid derivatives (pirimiphos-methyl and pyrazophos) reduced the formation of aflatoxin B2 and G2 but B1 and G1 and anthraquinones accumulated. Phosphorodithioic acid derivatives (dimethoate and malathion) blocked aflatoxin B2, reduced B1 and G2 but G1 and anthraquinones accumulated. Phosphoric acid derivative (profenfos) inhibited the formation of all aflatoxins, versicolorin A and versiconal hemiacetal acetate but averufin accumulated. The phenylurea derivatives (linuron and pencycuron) at concentrations of 500 and 1000 ppm inhibited all aflatoxin but anthraquinones accumulated. On the other hand, the dicarboximide derivative (iprodione) inhibited the whole pathway in the mutant strains of A. parasiticus. The oxidase system in wild-type A. flavus was active in the conversion of averufin and versicolorin A into aflatoxin B1. Most organophosphate and phenylurea derivatives may competitively increase or decrease the oxidase enzymes, however, profenfos and iprodione blocked the enzymes between averufin and versicolorin A.

Aflatoxins↗
PubMed1999

Genotoxicity testing of six insecticides in two crosses of the Drosophila wing spot test.

Among the great variety of genotoxicity assays available, the wing spot test in Drosophila melanogaster has some characteristics that make it very suited for the screening of genotoxic activity, i.e., it is an easy and inexpensive assay using a eukaryotic organism in vivo. One of the most interesting characteristics of the assay is its capacity to detect genotoxic activity of promutagens without the necessity of an exogenous metabolic activation system. In this paper we present results obtained with a recently developed high bioactivation cross of the wing spot test (NORR cross). The positive results obtained with the five well-known procarcinogens 7, 12-dimethylbenz[a]anthracene, N-nitrosopyrrolidine, p-dimethylaminoazobenzene, diethylnitrosamine and urethane clearly show that the NORR strains are similar to the other high bioactivation strains previously described, but they lack their methodological disadvantages. We have tested six insecticides, which are characterised by having contradictory results in other genotoxicity tests, using both the standard and the high bioactivation (NORR) cross. The six insecticides analysed are the pyrethroid allethrin, the methylenedioxyphenolic compound piperonyl butoxide, the chlorinated hydrocarbons dieldrin and endrin, and the organophosphates dimethoate and malathion. We obtained negative results for all six compounds. Our results show the suitability of the wing spot test for the evaluation of compounds at the first level of genotoxicity testing.

Animals↗
PubMedDate not supplied

Syntheses of haptens containing dioxaphosphorinan methoxyacetic acid linker arms for the production of antibodies to organophosphate pesticides.

Four generic heterobifunctional reagents, namely 2-(2-chloro-5-methyl-1,3,2-dioxaphosphorinan-5-yl)methoxyacetic acid methyl ester, p-sulfide, 2-(2-chloro-5-methyl-1,3,2-dioxaphosphorinan-5-yl)-methoxyacetic acid methyl ester, p-oxide, 2-(2-mercapto-5-methyl-1,3,2-dioxaphosphorinan-5-yl)-methoxyacetic acid bispotassium salt, p-sulfide-, and (2-methoxy-5-methyl-1,3,2-dioxaphosphorinan-5-yl)methoxyacetic acid, methyl ester, have been synthesized and used to prepare organophosphate, thiophosphate, and dithiophosphate haptens containing a functional carboxyl group which can be used to conjugate the haptens to proteins. These hapten-protein conjugates have been used as antigens for preparing polyclonal sera against all classes of organophosphate pesticides. The eight examples used protein-hapten conjugates of chlorpyrifos, parathion, diazinon, paraoxon, azinphos, dimethoate, demeton, and dichlorvos. These were all immunogenic and resulted in sera containing antibodies that recognized the corresponding parent pesticide with high specificity.

Acetates↗
PubMed2005

Current-use and legacy pesticide history in the Austfonna Ice Cap, Svalbard, Norway.

The Svalbard archipelago in arctic Norway receives considerable semivolatile organic contaminant (SOC) inputs from the atmosphere. To measure the history of net SOC accumulation there, we analyzed the upper 40 m of an ice core from Austfonna, the largest ice cap in Eurasia, for several legacy organochlorine (OC) compounds and current-use pesticides (CUPs) including organophosphorus (OP), triazine, dinitroaniline, and chloroacetamide compounds. Five OP compounds (chlorpyrifos, terbufos, diazinon, methyl parathion, and fenitrothion), two OCs (methoxychlor and dieldrin), and metolachlor--an herbicide--had historical profiles in the core. The highest OC concentration observed was aldrin (69.0 ng L(-1)) in the surface sample (1992-1998). The most concentrated OP was dimethoate (87.0 ng L(-1)) between 1986 and 1992. The surface sample also had highest concentrations of pendimethalin (herbicide, 18.6 ng L(-1)) and flutriafol, the lone observed fungicide (9.6 ng L(-1)). The apparent atmospheric persistence of CUPs likely results from little or no oxidation by OH* during the dark polar winter and in spring. Long-range atmospheric pesticide transport to Svalbard from Eurasia is influenced by the positive state of the North Atlantic Oscillation Index since 1980 and also by occasional fast-moving summer air masses from northern Eurasian croplands.

Atmosphere↗
PubMed2000

Comparative toxicity of selected organophosphate insecticides against resistant and susceptible clones of the greenbug, Schizaphis graminum (Homoptera: aphididae).

Comparative toxicity of selected organophosphate (OP) insecticides against resistant and susceptible clones of the greenbug, Schizaphis graminum, were studied both in vitro and in vivo. Two resistant (OR-1 and OR-2) clones of the greenbug showed marginal to high levels of resistance to all seven OPs tested, ranging from 11- to 327-fold greater than those of a susceptible (OSS) clone. The OR-1 clone showed lower levels of resistance to phenyl (parathion and parathion-methyl) and heterocyclic (chlorpyrifos) OPs than to aliphatic OPs (dimethoate, omethoate, disulfoton, and demeton-S-methyl), whereas the OR-2 clone showed a rather broad spectrum of resistance to nearly all OP insecticides examined. In vitro inhibition of acetylcholinesterase (AChE) using six selected OP oxon analogues showed that alterations of AChE were involved in resistance to all OP compounds examined in both the OR-1 and OR-2 clones. Although the levels of insensitivity of AChE to these OPs were relatively low, ranging from 1.1- to 3.8-fold, the insensitivity spectrum of AChE to different OPs was rather broad. The general esterase activity in the OR-1 and OR-2 clones was 1.3-8. 4-fold higher than that in the OSS clone, depending on the substrates used. The AChE activity in both the OR-1 and OR-2 clones was 1.8-fold higher than that in the OSS clone. High resistance levels of the OR-2 clone to phenyl and heterocyclic OPs appeared to be associated with the ability of the esterases to hydrolyze beta-naphthyl acetate and more hydrophobic substrates.

Acetylcholinesterase↗