1,720,966 research outputs found
High-performance liquid chromatographic mass spectrometric identification of the photoproducts of cymoxanil.
No full textThe photochemical degradation of the fungicide cymoxanil {2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino) acetamide} was studied in aqueous buffer solution (pH 5.9 ± 0.1) under UV light and in laboratory conditions. The degradation followed a pseudo-first-order kinetic with significant correlation coefficient. The main photoproducts were separated and tentatively identified by HPLC/UV and HPLC/MS data, as 3-ethyl-4-(methoxyamino)-2,5-dioxo-4-imidazolidinecarbonitrile, 1-ethyl-5-(methoxyimino)-2,4-imidazolidin-2,4-dione, ethylimidazolidinetrione and {[(ethylamino)carbonyl]-amino}oxoacetic acid. A photolysis pathway of cymoxanil is proposed
Identification of photoproducts from imazosulfuron by HPLC
No full textPhotolysis of imazosulfuron was studied in aqueous solution under UV light. The reaction followed a pseudo-first-order kinetic with significant correlation coefficient. The major photodegradation products of imazosulfuron after irradiation under UV light were separated and tentatively identified by HPLC-MS analysis as (4,6-dimethoxypyrimidine-2-yl)aminocarbonylsulfamic acid, 4,6-dimethoxy-2-ureidopyrimidine and 2,2'-dichloro-[3,3'] bi [imidazo[1,2-a] pyridinyl]. The results indicate that different reaction pathways are followed: (1) cleavage of the sulfonylurea bridge; (2) desulfonylation, which can proceed either by a carbon-sulfur cleavage or a nitrogen-sulfur cleavage. A mechanism for the formation of the photoproducts is proposed
Liquid chromatographic determination of nine N-methylcarbamates in drinking water.
No full textA multi-residue method for the simultaneous extraction from drinking water using solid-phase extraction on LiChrolut EN [poly(styrene-divinylbenzene), PSDVB] and determination of nine N-methylcarbamate pesticides (NMCs) (aldicarb, its metabolites i.e. aldicarb sulfone and aldicarb sulfoxide and carbaryl, carbofuran, dioxacarb, ethiofencarb, methomyland propoxur) using reversed-phase liquid chromatography was studied. A 1000-fold pre concentration was achieved and the method was used for determination of the nine pesticides in water, with limits of detection in the range 3–15 ng L−1. For all compounds the recoveries determined at the 0.1 and 1 μg L−1 level generally ranged from 85 to 104% with relative standard deviations (RSD) of 1.4–8.8%
Bensulfuron:preliminary test of photolysis.
No full textPhotodegradation of bensulfuron methyl, ( methyl-alfa-4,6-dimethoxypyrimidin-2-carbamoylsulfamoyl)-o-toluate ester) was carried out in aqueous solution under UV light. The rate of photolysis followed a first order kinetic. The main metabolites in distilled were tentatively idenified with a Diode Array Detector (DAD) and mass spectometry (MS) as (4,6-dimethoxy-2-pyrimidinyl)urea (1), methyl-alfa-4,6-dimethoxy-2-pyrimidinyl)amino-o-toluate 4) and alfa-sulfamoyl-o-toluic acid (2) that cyclises to 2-mthylsulfonylbenzoic acid imine (3). A mechanism which accounts for the formation of photoproducts is propose
Photodegradation of bensulphuron methyl in aqueous solution
No full textPhotodegradation of bensulphuron methyl, (methyl -(4,6-dimethoxypyrimidin-2-carbamoylsulphamoyl)-o-toluate ester) was carried out in aqueous solution under UV light. The rate of photolysis followed first-order kinetics, with a half-life of 31.7 min at λ = 254 nm and 41.3 h at λ ≥ 290 nm, with significant correlation coefficients (0.9898 and 0.9625, respectively). The main photoproducts in distilled water were identified with a diode array detector and mass spectrometry. The results indicate that different reaction pathways are followed: cleavage of the sulphonylurea bridge, desulphonylation, which can proceed either by a carbon-sulphur cleavage or a nitrogen-sulphur cleavage and contraction of the sulphonylurea bridge. A mechanism which accounts for the formation of the photoproducts is propose
Determination of cymoxanil in drinking water and soil using high-performance liquid chromatography.
No full textWe describe a method for determination of cymoxanil, 1-2-cyano-2-methoxy(iminoacetyl)-3-ethylurea, in drinking water and in soil, using reversed-phase HPLC with UV detection at 240 nm and a mobile phase of acetonitrile-water (30:70, v/v). Fortified water samples (1.0 L) were extracted with solid-phase extraction on Strata X. Soil samples (20 g) were extracted with acetone and the extracts were transferred onto Strata C18E. The recoveries of cymoxanil from water and soil samples were over 85% for each fortification level. The RDS were within the range 1.7-4.1% for water and 0.9-1.2% for soil samples. After optimization of the extraction and separation conditions, the method was validated
Analysis of nicotinoid insecticides residues in honey by solid matrix partition clean-up and liquid chromatography-electrospray mass spectrometry.
No full textAn analytical method for the routine simultaneous determination of four nicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid and thiamethoxam) in commercial multifloral honey was developed. Fortified honey samples, dissolved in water, were cleaned up through Extrelut NT20 column and, finally, insecticides were eluted with dichloromethane. The eluate was evaporated, the residue redissolved in methanol and then analyzed by LC–ESI(+)-MS. Average recoveries of the four analytes were in the range of 76% and 99% at both spiking levels 0.1 and 1.0 mg kg−1. Relative standard deviations (RSDs) were less than 10% for all of the recovery tests. The detection limits (LODs) of the method ranged from 0.01 to 0.1 mg kg−1 for the different insecticides studied. The developed method is linear over the range assayed, 0.5–5.0 gmL−1, with linear correlation coefficients higher than 0.9993
Multiresidue determination of nicotinoid insecticide residues in drinking water by liquid chromatography with electrospray ionization mass spectrometry
No full textA multianalyte method has been developed for the confirmation and quantification of four neonicotinoids, acetamiprid, imidacloprid, thiacloprid and thiamethoxam in drinking water. These insecticides were extracted from water by solid-phase extraction (SPE) LiChrolut EN. Analytes’ determination and quantification were performed by liquid chromatography–mass spectrometry (LC–MS). Extraction efficiency experiments demonstrated the ability of this method to extract nicotinoids from water samples. Confirmatory analysis was carried out by LC-electrospray ionization–mass spectrometry (LC-ESI–MS) instrumentation equipped with a single-quadrupole mass filter. MS data acquisition was performed by two-ion selected ion monitoring (SIM) program. Average recoveries of the four analytes from drinking water samples were in the range of 95 and 104% with relative standard deviations (R.S.D.) < 20%. The limit of quantification (LOQ) for each of the four insecticides was 0.03 microgL−1
Determination of neonicotinoid insecticides residues in bovine milk samples by solid-phase extraction clean-up and liquid chromatography with diode-array detection
No full textIn this paper we have developed an analytical method for the simultaneous determination of four nicotinoid insecticides [acetamiprid (ACT), imidacloprid (ICL), thiacloprid (TCL) and thiamethoxam (TMX)] in bovine whole milk. These analytes were extracted, in a single step with dichloromethane, from fortified milk samples, using Chem Elut cartridges, containing diatomaceous earth material. Insecticide's determination and quantification were performed by HPLC with diode-array detection (DAD). Average recoveries of the four insecticides from bovine milk samples were between 85.1 and 99.7% at spiking levels 0.01, 0.05 and 0.1mgkg(-1). Relative standard deviations (RSDs) were no larger than 10% for all of the recovery tests. The calculated limits of quantitation (LOQ) ranged from 0.01 to 0.04mgkg(-1) for the four insecticides, being equal to or lower than the maximum residue limits (MRLs) established by European legislation (0.01-0.05mgkg(-1)). The developed method is linear at concentrations within the tested interval, with coefficients of determination higher than 0.9990. According to Commission Decision 2002/657/EC, decision limit (CCalpha) and detection capability (CCbeta) have been calculated. The proposed method is rapid, simple and could be utilized for the routine analysis of pesticides residues
Development and validation of a solid-phase extraction method coupled to high-performance liquid chromatography with ultraviolet-diode array detection for the determination of sulfonylurea herbicide residues in bovine milk samples
No full textThis study proposes a fast, simple and sensitive liquid chromatography diode array detector (LC/UV-DAD)-based method for the simultaneous determination of eight sulfonylurea herbicides (bensulfuron methyl, chlorsulfuron, metsulfuron methyl, primisulfuron methyl, rimsulfuron, thifensulfuron methyl, triasulfuron and tribenuron methyl) in bovine whole milk at concentrations lower than the default limit of 0.01 mg kg(-1) allowed by current legislation (Regulation EC/396/2005 and following Annexes). An effective one-step solid phase extraction (SPE) and clean up procedure was defined with use of Chem Elut cartridges, providing good recoveries for all the analytes tested and with no matrix effects affecting method accuracy. Separation of herbicides was obtained on a C(18) column by acetonitrile- water gradient elution. Method validation has been performed according to European Commission Decision 2002/657/EC criteria, in terms of linearity, recovery, precision, specificity, decision limit (CC(α)) and detection capability (CC(β)). Typical recoveries ranged between 78.4% and 99.7%, at the maximum residue limits (MRLs) levels established by Regulation EC/396/2005, with relative standard deviations (RSD) no larger than 10%
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