Search results for "pesticide residues"
showing 10 items of 89 documents
Determination of carbamate residues in fruits and vegetables by matrix solid-phase dispersion and liquid chromatography-mass spectrometry.
2000
Abstract Thirteen carbamates were analysed in orange, grape, onion and tomatoes by matrix solid-phase dispersion (MSPD) followed by liquid chromatography–mass spectrometry (LC–MS). Electrospray (ES) and atmospheric pressure chemical ionisation (APCI) were compared and both gave similar results in terms of sensitivity and structural information because at 20 V fragmentor voltages the fragmentation is minimal. The efficiency of different solid-phases (C18, C8, cyano, amine and phenyl) for the MSPD was compared. Mean recoveries using C8 varied from 64 to 106% with relative standard deviations of 5–15% in the concentration range of 0.01–10 mg kg−1. Matrix constituents did not interfere signific…
Analysis of organophosphorus pesticides in honeybee by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.
2001
Pesticides applied in extended agricultural fields may be controlled by means of bioindicators, such as honeybees, in which are the pesticides bioaccumulate. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) experiments with positive (PI) and negative (NI) ion modes were optimized for the analysis of 22 organophosphorus pesticides in honeybee samples. The extraction required 3 g of sample, which was extracted with acetone. The extract was purified with coagulating solution and reextracted with Cl(2)CH(2). Pesticides studied could be detected by both ionization modes except for parathion, parathion-methyl, and bromophos, which did not give signals …
Miniaturized matrix solid phase dispersion procedure and solid phase microextraction for the analysis of organochlorinated pesticides and polybromina…
2009
Abstract This work has developed a miniaturized method based on matrix solid phase dispersion (MSPD) using C18 as dispersant and acetonitrile–water as eluting solvent for the analysis of legislated organochlorinated pesticides (OCPs) and polybrominated diphenylethers (PBDEs) in biota samples by GC with electron capture (GC-ECD). The method has compared Florisil®-acidic Silica and C18 as dispersant for samples as well as different solvents. Recovery studies showed that the combination of C18–Florisil® was better when using low amount of samples (0.1 g) and with low volumes of acetonitrile–water (2.6 mL). The use of SPME for extracting the analytes from the solvent mixture before the injectio…
Solid-Phase Microextraction Liquid Chromatography/Tandem Mass Spectrometry To Determine Postharvest Fungicides in Fruits
2003
A method to determine five postharvest fungicides (dichloran, flutriafol, o-phenylphenol, prochloraz, tolclofos methyl) in fruits (cherries, lemons, oranges, peaches) has been developed using solid-phase microextraction (SPME) coupled to liquid chromatography (LC) with photodiode array (DAD), mass spectrometry (MS), or tandem mass spectrometry (MS/MS) with ion trap detection. Extraction involved sample homogenization with an acetone/water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. The pesticides were isolated with a fused-silica fiber coated with 50-microm Carbowax/template resin. The effects of pH, ion strength, sample volume, and extraction time were in…
Determination of amitraz and its transformation products in pears by ethyl acetate extraction and liquid chromatography-tandem mass spectrometry.
2008
A method has been developed for identification and quantification of the acaricide amitraz and its transformation products, 2,4-dimethylaniline (DMA), 2,4-dimethylformamidine (DMF) and N-2,4-dimethylphenyl-N-methylformamidine (DMPF) in pears. The analytes were extracted using ethyl acetate and anhydrous sodium sulphate. Analysis was performed by liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) in the positive ion mode using a triple quadrupole (QqQ) instrument. Two precursor-product ion transitions were monitored for each compound in the selected reaction monitoring (SRM) mode. The method was validated with pears taken from the orchard before the amitraz treatment …
Rapid and sensitive ultra-high-pressure liquid chromatography-quadrupole time-of-flight mass spectrometry for the quantification of amitraz and ident…
2008
Liquid chromatography under high pressure in combination with quadrupole time-of-flight mass spectrometry (QqTOF-MS and MS/MS) has been used to detect amitraz degradation products in pears, to characterize their structures, and to evaluate their occurrences in samples of different origins. Using the proposed approach, the parent pesticide and four degradation products were identified. To this end, pear samples were extracted with ethyl acetate and anhydrous sodium sulphate. Amitraz was found to be rapidly decomposed into four related compounds, of which N-(2,4-dimethylphenyl)formamidine (DMPF) was the most abundant and persistent. N,N'-bisdimethylphenylformamidine (BDMPF), 2,4-dimethylforma…
Development of monoclonal antibody-based competitive immunoassays for the detection of picoxystrobin in cereal and oilseed flours
2012
Picoxystrobin is a new generation fungicide primarily developed to be used in cereal crops. In the present study a novel collection of specific monoclonal antibodies has been produced using different immunizing haptens based on a carboxy-functionalized identical spacer arm attached to alternative positions of the target pesticide molecule. Two competitive enzyme-linked immunosorbent assays have been developed employing hapten heterology, one using the antibody-coated direct format and the other in the conjugate-coated indirect format. Both immunoassays have been characterized in terms of selectivity, solvent tolerance, and buffer conditions, affording similar limits of detection at or below…
Matrix solid-phase dispersion extraction procedure for multiresidue pesticide analysis in oranges.
1996
A multiresidue extraction method based on matrix solid-phase dispersion (MSPD) is optimized for the extraction and gas chromatographic screening of eighteen insecticides (aldrin, carbophenothion, captafol, chlorpyriphos, chlorfenvinphos, diazinon, dicofol, alpha-endosulfan, beta-endosulfan, ethion, fenitrothion, folpet, methidathion, malathion, methyl-azinphos, methyl-parathion, phosmet, and tetradifon) from oranges. After optimization of different parameters, such as type of solid phase used and the amount of solid phase or eluent, recoveries ranged from 67 to 102% with relative standard deviations ranging from 2 to 10%. The limits of detection, calculated as 3 times the baseline noise ran…
Evaluation of solid-phase extraction and stir-bar sorptive extraction for the determination of fungicide residues at low-microg kg(-1) levels in grap…
2004
Abstract A liquid chromatography–mass spectrometry method has been developed for determining bitertanol, carboxin, flutriafol, pyrimethanil, tebuconazole and triadimefon. The evaluation of both atmospheric pressure interfaces (API), atmospheric pressure chemical ionization (APCI) and electrospray (ESI) using positive and negative ionization modes, clearly shows that the studied pesticides are more sensitive using APCI in positive mode. Two procedures based on solid-phase extraction (SPE) and stir-bar sorptive extraction (SBSE) have been assessed for extracting these compounds in grape. The recoveries obtained by SPE in samples spiked at the limit of quantification (LOQ) level ranged from 60…
Analysis of thiabendazole and procymidone in fruits and vegetables by capillary electrophoresis–electrospray mass spectrometry
2002
Abstract A capillary electrophoresis–mass spectrometry method for determining procymidone and thiabendazole in apples, grapes, oranges, pears, strawberries and tomatoes is described. Separation is achieved using a buffer of formic acid–ammonium formate at pH 3.5 with 2% of methanol. Fungicide residues present in the sample are preconcentrated by both solid-phase extraction and injection of large sample volumes into the capillary by a stacking technique, to obtain lower detection limits. Ionization is performed at atmospheric pressure in an electrospray type source and detection is carried out using positive ionization and selected ion monitoring modes. The quantitation limits are 0.005 and …