Photodegradation of fenitrothion and parathion in tomato epicuticular waxes

Photodegradation of (14)C-labeled fenitrothion ([O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate]) and parathion ([O,O-diethyl O-(4-nitrophenyl) phosphorothioate]) was conducted on a series of solid surfaces including isolated tomato fruit and leaf cuticle waxes. The wax-coated glass plate gave the comparative degradation of fenitrothion observed for the intact plant but both surfaces of octadecyl-capped silica gel and poly(tetrafluoroethylene) enhanced its volatilization. Photoinduced desulfuration and ester cleavage were common to both pesticides in waxes, but formation of the azo derivative was found to be a major degradation pathway characteristic of parathion. The modified electronic states of the nitro group by introduction of m-methyl group accounted for this different photoreactivity based on molecular orbital calculations.     

Comparison of soxhlet and microwave-assisted extractions for the determination of fenitrothion residues in beans

White and black "niebe" beans [Vigna unguiculata (L.) Walp] from Senegal were treated with fenitrothion (O,O-dimethyl O-4-nitro-m-tolyl phosphorothioate), and the residues were determined by high-performance liquid chromatography (HPLC) and electron capture gas chromatography (EC-GC). Fenitrothion residues from the beans were extracted by Soxhlet extraction (SE) and microwave-assisted extraction (MAE). A column cleanup procedure was used to remove the coextractives in the extract before HPLC and EC-GC analyses. The overall mean recoveries of fenitrothion residues in the 0.19-1.90 microg/kg fortification range determined from extracts obtained by SE and MAE were 88.4 and 89.8%, respectively, with respective relative standard deviations of <4%. The results show that MAE is a viable alternative to the commonly used SE for the determination of fenitrothion residues in beans.     

On-column partition cleanup of fatty extracts for organophosphate pesticide residue determination

A fast, single-step, and efficient partition between n-hexane and acetonitrile on ready-to-use, disposable mini-columns of Kieselghur-type material has been developed for the cleanup of fatty extracts for organophosphate (OP) pesticide residue determination by gas chromatography with flame photometric detection. Nine OP pesticides (diazinon, etrimfos, chlorpyrifos-methyl, pyrimiphos-methyl, chlorpyrifos, bromophos, bromophos-ethyl, malathion, fenitrothion) most commonly used for protection of stored cereals, oil seeds, and legumes were separated from up to 2.0 g lipidic material with recoveries between 80 and 107% at spiking levels ranging for the different compounds from 0.1 to 5.0 ppm.     

Gas chromatographic method for determination of fenitrothion in technical and in emulsifiable concentrate and water-dispersible powder formulations: collaborative study

A variety of column packings and internal standards were evaluated to determine the most satisfactory system to use in a gas chromatographic (GC) method for analysis of fenitrothion, technical and formulations. Fenitrothion and the most closely related isomer, O,O-dimethyl O-(4-methyl-3-nitrophenyl) phosphorothioate, were resolved on columns packed with OV-210 and with polyphenyl ether, 6-ring (PPE-6R). A method based on the separation of fenitrothion on a PPE-6R column with fluoranthene as internal standard was selected for use in a limited collaborative trial and later for use in a full-scale collaborative trial with 21 collaborators participating. Each collaborator was furnished matched pairs of samples of technical fenitrothion, emulsifiable concentrate, and water-dispersible powder. The coefficients of variation (CV) for the paired samples were 1.02, 1.11, and 1.01, respectively, for technical fenitrothion, emulsifiable concentrates, and water-dispersible powders. Data are also presented for an alternative method in which compounds are separated on an OV-210 column with dibutyl sebacate as the internal standard. The method has been adopted official first action.     

Matrix-Based Fertilizers Reduce Pesticide Leaching in Soil

The presence of pesticides in groundwater has been documented in several large-scale studies and numerous small-scale investigations. Pesticide leaching through soil has been identified as a major cause for the occurrence of these chemicals in surface and groundwater. We developed matrix-based fertilizers (MBFs) that have been shown to reduce N and P leaching. We tested the efficacy of the ionic bonds in the MBFs to reduce 2,4-dichlorophenoxyacetic acid (2,4-D), metolachlor, thiophanate methyl, carbaryl, diazinon, and malathion leaching in soil columns. After 7 days 2,4-D, thiophanate methyl, carbaryl, and malathion did not leach in sufficient quantities to determine if the MBF fertilizers reduced leaching compared with the control and the slow-release fertilizer Polyon®. The MBF fertilizers leached from five to 30 times less metolachlor than the control and Polyon® treatment. Treatments with MBF fertilizers leached from two to 72 times less diazinon than the control treatment. The MBF fertilizer treatment leached from eight to 268 less diazinon than columns receiving Polyon®. The MBF formulations allow compounds with both anionic and cationic charges to bind with the Al(SO₄)₃ 3H₂O and/or Fe₂(SO₄)₃ 3H₂O-lignin-cellulose matrix. When pesticides are added to the soil amended with matrix-based fertilizers, the ion exchange matrix will likely bind the metolachlor and diazinon to the Al(SO₄)₃ 3H₂O and/or Fe₂(SO₄)₃ 3H₂O-starch-cellulose-lignin matrix thereby substantially reducing leaching. The MBFs could be used to limit both nutrients and pesticide leaching from agricultural fields.     

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%.     

Biodegradation and persistence of several acetamide,acylanilide, azide,carbamate, and organophosphate pesticide combinations

The effect of potassium azide (KN₃), O,O-diethyl O-(2-isopropyl-6-methyl-4-pyrimidinyl) phosphorothioate (diazinon), O,O-diethyl S-[(ethylthio)- methyl] phosphorodithioate (phorate), 1-naphthyl methylcarbamate (carbaryl), and p-chlorophenyl methylcarbamate (PCMC) on the biodegradation and persistence of several amide, carbamate, and urea herbicides in soil and microbial culture systems was examined. KN₃ inhibited the biodegration of isopropyi m-chlorocarbanilate (chlorpropham) in both soil perfusion and microbial culture system, but was limited in increasing chlorpropham persistence in soil under greenhouse conditions. PCMC and diazinon, inhibited the metabolism of chlorpropham by isolated cultures of soil bacteria (Pseudonwnas striata Chester and Achromobacter sp). Phorate inhibited chlorpropham metabolism by P. striata, but did not inhibit chlorpropham metabolism by Achromobacter sp. Carbaryl, PCMC, and diazinon increased the persistence of chlorpropham in soil under greenhouse conditions. PCMC also inhibited the microbial metabolism of isopropyl carbanilate (propham), 3',4'-dichloropropionanilide (propanil), 2-chloro-N,N-diallylacetamide (CDAA), 1,1-dimethyl-3 (α,ga,α-trifluoro-m-tolyl)urea (fluometuron) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), but not that of 2-chloro-N-isopropylacetanilide (propachlor) in isolated culture systems.     

HPLC analysis of sesaminol glucosides in sesame seeds

An HPLC method was developed and validated for the quantification of sesaminol triglucoside and a sesaminol diglucoside in sesame seeds. These two lignans were isolated, and their structures were characterized by mass and nuclear magnetic resonance spectroscopy. Defatted sesame flour was extracted first with 85% ethanol for 5 h followed by 70% ethanol for 10 h at room temperature using naringenin as internal standard. Analysis of 65 different samples of sesame seeds indicated that the content of sesaminol triglucoside ranged from 36 to 1560 mg/100 g of seed (mean 637 +/- 312) and that of sesaminol diglucoside ranged from 0 to 493 mg/100 g of seed (mean 75 +/- 95). No significant difference was found between sesaminol glucoside contents in black and white seeds.     

Policosanol content and composition in perilla seeds

Policosanols, long-chain alcohols, have many beneficial physiological activities. Contents and compositions in perilla seeds (Perilla frutescens) produced in Korea and China were determined. Waxy materials were extracted from perilla seeds using hot hexane. Yield of the waxy materials from perilla seeds was 72.1 mg/100 g of dry weight. Contents and compositions of the waxy materials and policosanols were identified and quantified by TLC, HPLC, and GC. Major components of the waxy materials from Korean and Chinese perilla seeds were policosanols (25.5 and 34.8%, respectively), hydrocarbons (18.8 and 10.5%), wax esters, steryl esters and aldehydes (53.0 and 49.8%), acids (1.7 and 2.1%), and triacylglycerols (1.0 and 2.9%), determined by HPLC. For comparison, waxy materials of sesame seeds were also analyzed. Yield of the waxy materials from sesame seeds were 8.6 mg/100 g. Less than 5% policosanols were detected in the waxy materials extracted from sesame seeds produced in Korea and China. Wax esters or steryl esters accounted for 93-95% of the sesame waxy materials. Policosanols in the perilla seeds were composed of 67-68% octacosanol, 16-17% hexacosanol, 6-9% triacontanol, and others.     

Simultaneous gas chromatographic determination of carbofuran, metalaxyl, and simazine in soils

A method for extraction, cleanup, and simultaneous gas chromatographic detection of carbofuran, metalaxyl, and simazine in soils has been developed. Pesticide residues were extracted from soil with acetone containing 10% 0.2M HCl-KCl buffer (pH 2.0), cleaned up with methylene chloride-carbonate buffer (pH 10.7) solvent partitioning and solid-phase extraction on disposable silica gel columns, and quantitated with gas chromatography using a Supelcowax 10 megabore capillary column and a nitrogen-selective detector. Method limits of detection were 0.02 microgram/g for the 3 pesticides in surface soils (0-30 cm depths) and 0.02, 0.02, and 0.005 microgram/g in soils below 30 cm (subsoils) for carbofuran, metalaxyl, and simazine, respectively. Recoveries for carbofuran, metalaxyl, and simazine were 92.6 +/- 5.5, 93.6 +/- 5.0, and 88.4 +/- 6.7%, respectively, when soil samples were spiked with pesticide concentrations ranging from 0.02 to 2.0 micrograms/g.     

Flame absorption spectroscopic determination of cadmium, copper, iron, lead, and zinc in mussels

A rapid method is proposed for determination of Cd, Cu, Fe, Pb, and Zn in mussel samples. The elements are extracted with concentrated nitric acid in borosilicate glass tubes at 90 degrees C for 1 h, and determined by flame atomic absorption spectroscopy. Detection limits for a 300 mg sample corresponded to 0.3 microgram Cd/g, 0.7 microgram Cu/g, 33 microgram Fe/g, 0.7 microgram Pb/g, and 6 micrograms Zn/g. The coefficient of variation for 20 independent analyses was 7% for Cd, 7% for Cu, 6% for Fe, 14% for Pb, and 8% for Zn. Recoveries were 107 +/- 3% for Cd, 90 +/- 3% for Cu, 94 +/- 1% for Fe, 90 +/- 5% for Pb, and 96 +/- 3% for Zn. The accuracy of the method was determined by analyzing NBS Oyster Tissues.     

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.     

Metabolism of fenitrothion and conjugation of 3-methyl-4-nitrophenol in tomato plant (Lycopersicon esculentum)

The metabolism of (14)C-labeled fenitrothion (Sumithion, [O,O-dimethyl-O-(3-methyl-4-nitrophenyl)phosphorothioate]) in tomato plant (Lycopersicon esculentum Mill., cv. Ponderosa) grown in the greenhouse equipped with quartz glass was conducted to investigate the effect of sunlight on the behavior of fenitrothion and to elucidate the detailed structure of conjugated metabolites. Tomato plants (BBCH 85) were topically treated with (14)C-labeled fenitrothion twice with a 2 week interval between applications. At 15 days after the second application, more than half of the recovered (14)C was detected as unaltered fenitrothion, glucose, and cellobiose esters of 3-methyl-4-nitrophenol (NMC) in extracts from tomato fruit. The photoinduced formation of the S-methyl isomer of fenitrothion via thiono-thiolo rearrangement was detected only in the surface rinse but at trace amounts. In the whole tomato fruit, fenitrothion, the S isomer, NMC-beta-glucoside, and NMC cellobioside were detected at 34.16, 1.28, 7.47, and 15.07% of the recovered (14)C, respectively. Trace amounts of the oxon analogue of fenitrothion were detected only on tomato leaves. The chemical structure of the cellobiose conjugate of NMC, 1-O-beta-d-glucopyranosyl-(1-->4)-beta-d-glucopyranosyl-3-methyl-4-nitrophenol, was determined by spectroscopic analyses (liquid chromatography-mass spectrometry, NMR), using the metabolite obtained from leaves and stems of tomato plant hydroponically grown with (14)C-labeled NMC.     

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.     

Kinetics and hydrolysis of fenamiphos, fipronil, and trifluralin in aqueous buffer solutions.

Hydrolyses of fenamiphos, fipronil, and trifluralin were studied in aqueous buffer solutions of pH 4.1, 7.1, and 9.1 at different temperatures, 5, 22 +/- 1, 32 +/- 1, and 50 +/- 1 degrees C. Fenamiphos, fipronil, and trifluralin were found to be more stable in acidic and neutral buffer solutions at temperatures of 5 and 22 +/- 1, and dissipation is rapid at 50 +/- 1 degrees C. In basic buffer and at higher temperature, degradation of fenamiphos was found to be very rapid when compared with fipronil and trifluralin. The rate constants calculated at 32 degrees C for fenamiphos were 2349.4 x 10(-)(8) (pH 4.1), 225.2 x 10(-)(8) (pH 7.1), and 30476.0 x 10(-)(8) (pH 9.1); for fipronil 1750.0 x 10(-)(8) (pH 4.1), 3103.0 x 10(-)(8) (pH 7.1), and 3883.0 x 10(-)(8) (pH 9.1); and for trifluralin 2331.0 x 10(-)(8) (pH 4.1), 2360.0 x 10(-)(8) (pH 7.1), and 3188.0 x 10(-)(8) (pH 9.1). On the basis of rate constant values, these pesticides appeared to be more susceptible to hydrolysis than synthetic organophosphorus compounds such as chlorpyriphos, diazinon, malathion, and ronnel. DT(50) values calculated at 32 degrees C were 228 (pH 4.1), 5310.24 (pH 7.1), and 37.68 (pH 9.1) h for fenamiphos; 608.6 (pH 4.1), 373.9 (pH 7.1), and 270.2 (pH 9.1) h for fipronil; and 502.1 (pH 4.1), 496.8 (pH 7.1), and 355.7 (pH 9.1) h for trifluralin.     

Cloning, functional expression, and characterization of cystatin in sesame seed

A cDNA fragment encoding cystatin, a cysteine protease inhibitor, was obtained from maturing sesame seeds. The clone was constructed in a nonfusion or fusion vector and then overexpressed in Escherichia coli. The recombinant cystatins were found in the soluble fraction of cell extract and were demonstrated to be functionally active in a reverse zymographic assay. The corresponding endogenous 22 kDa cystatin of low abundance in mature seeds was purified to homogeneity via a papain-coupling affinity column and confirmed by western blotting with antibodies against the recombinant cystatin. Both endogenous and recombinant cystatin proteins showed effective inhibitory activities against papain with K(i) values of 7.89 x 10(-8) M and 2.77 x 10(-8) M, respectively. Immunodetection indicated that cystatin was specifically expressed in maturing seeds and rapidly degraded in germination. Accordingly, zymographic and inhibition analyses showed that sesame cystatin could not inhibit the de novo synthesized proteases in germinating seeds. It is suggested that sesame cystatin may play a role in the regulation of endogenous cysteine proteases during seed maturation and germination.     

Purification and characterization of an esterase conferring resistance to fenitrothion in Oryzaephilus surinamensis (L.) (insecta, coleoptera, silvanidae)

Esterases from a fenitrothion-resistant strain (VOSF) of the saw-toothed grain beetle, Oryzaephilus surinamensis (L.), are presumed to play a role in conferring resistance to malathion, fenitrothion, and chlorpyrifos-methyl. Colorimetric assays showed a significant positive correlation between increased resistance to fenitrothion in strains of O. surinamensis examined and elevated esterase hydrolytic activity to substrates of p-nitrophenyl acetate, alpha-naphthyl acetate, and beta-naphthyl acetate. Esterase zymograms showed different banding patterns between VOSF and an insecticide-susceptible strain, VOS48. A major esterase in the VOSF strain, not detected in VOS48, was purified and characterized by chromatographic and electrophoretic techniques. On the basis of SDS-polyacrylamide gel eletrophoresis, the molecular mass of the purified esterase from VOSF was 130 kDa and consisted of two 65 kDa subunits. Additional properties of this enzyme are discussed.     

Identification of methanol-soluble compounds in sesame and evaluation of antioxidant potential of its lignans

The methanol extract of sesame (Sesamum indicum) seeds was fractionated and purified with the assistance of conventional column chromatography to afford 29 compounds including seven furofuran lignans. Among these isolates, (+)-samin (1) was obtained from the natural source for the first time. In addition, (-)-asarinin (30) and sesamol (31) were generated by oxidative derivation from (+)-sesamolin (2) and (+)-sesamin (3), two abundant lignans found in sesame seeds. To evaluate their in vitro antioxidant potential, the seven isolated lignans (1-7) and the two derivatives (30 and 31) were examined for the scavenging activities on DPPH free radicals and superoxide anions. Moreover, the capability of chelating ferrous ions and reducing power of these sesame lignans were also measured. The results suggest that, besides the well-known sesamolin and sesamin, the minor sesame lignans (+)-(7S,8'R,8R)-acuminatolide (5), (-)-piperitol (6), and (+)-pinoresinol (7) are also adequate active ingredients and may be potential sources for nutritional and pharmacological utilization.     

Assessment of the aroma impact of major odor-active thiols in pan-roasted white sesame seeds by calculation of odor activity values

Eleven odor-active thiols, namely, 2-methyl-1-propene-1-thiol, (Z)-3-methyl-1-butene-1-thiol, (E)-3-methyl-1-butene-1-thiol, (Z)-2-methyl-1-butene-1-thiol, (E)-2-methyl-1-butene-1-thiol, 2-methyl-3-furanthiol, 3-mercapto-2-pentanone, 2-mercapto-3-pentanone, 4-mercapto-3-hexanone, 3-mercapto-3-methylbutyl formate, and 2-methyl-3-thiophenethiol, recently identified in an extract prepared from white sesame seeds, were quantitated in sesame using stable isotope dilution analyses. For that purpose, the following deuterium-labeled compounds were synthesized and used as internal standards in the quantitation assays: [2H6]-2-methyl-1-propene-1-thiol, [2H3]-(E)- and [2H3]-(Z)-2-methyl-1-butene-1-thiol, [2H3]-2-methyl-3-furanthiol, [2H2]-3-mercapto-2-pentanone, [2H3]-4-mercapto-3-hexanone, [2H6]-3-mercapto-3-methylbutyl formate, and [2H3]-2-methyl-3-thiophenethiol. On the basis of the results obtained, odor activity values (OAVs) were calculated as ratio of the concentration and odor threshold of the individual compounds in cooking oil. According to their high OAVs, particularly the 3-methyl-1-butene-1-thiols (OAV: 2400) and the 2-methyl-1-butene-1-thiols (OAV: 960) were identified as the most odor-active compounds in pan-roasted white sesame seeds. These compounds were therefore suggested to be mainly responsible for the characteristic but rather unstable sulfury aroma of freshly pan-roasted white sesame seeds.     

Characteristic hydrocarbons and 2-alkylcyclobutanones for detecting gamma-irradiated sesame seeds after steaming, roasting, and oil extraction

Hydrocarbons and 2-alkylcyclobutanones in sesame seeds ( Sesamum indicum L.) irradiated at 0.5-4 kGy were used to determine the effect of subsequent steaming, roasting, and oil extraction from the roasted samples on the changes in their concentrations. The concentrations of radiation-induced hydrocarbons increased almost linearly (R(2) = 0.8671-0.9953) with the applied dose. The hydrocarbons, 1,7-hexadecadiene and 8-heptadecene, were detected only in the irradiated samples before and after three types of treatments at doses > or =0.5 kGy, but they were not detected in non-irradiated samples before and after treatment. These two hydrocarbons could be used as markers to identify irradiated sesame seeds. The concentrations of the three detected 2-alkylcyclobutanones, 2-dodecylcyclobutanone (2-DCB), 2-tetradecylcyclobutanone (2-TCB), and 2-(5'-tetradecenyl)cyclobutanone (2-TeCB), linearly increased with the irradiation dose. These compounds could be detected at doses > or =0.5 kGy but not in non-irradiated samples. The three types of treatments had no significant effect on the levels of 2-alkylcyclobutanones.