Search results for " Contamination"
showing 10 items of 571 documents
Application of accelerated solvent extraction followed by gel performance chromatography and high-performance liquid chromatography for the determina…
2005
Accelerated solvent extraction (ASE) has been evaluated as a fast alternative to methanolic saponification for the extraction of 12 polycyclic aromatic hydrocarbons (PAHs) from mussel tissue. Several solvent systems and different operating conditions were investigated. The mixture dichloromethane-acetone (1:1, v/v) gave the best recoveries at 125 degrees C and 1500 psi, in a total time of 10 min. No yield difference was found between freeze-drying (Fd) or drying the wet mussel with diatomaceous earth (Ded) prior to extraction. The ASE method was validated using the standard reference material SRM 2977, a freeze-dried mussel tissue with naturally present organic contaminants. The performance…
Measured and Modeled Residue Dynamics of Famoxadone and Oxathiapiprolin in Tomato Fields
2018
A reliable analytical method for the simultaneous determination of famoxadone and oxathiapiprolin dissipation kinetics as well as the metabolites of oxathiapiprolin (IN-E8S72 and IN-WR791) in tomato and soil was developed. We studied the dissipation of famoxadone and oxathiapiprolin in tomatoes grown using different kinetic curves in the area of Beijing in 2015 and 2016. Our results show that the most suitable model for two fungicides in 2015 and 2016 was first-order kinetic and second-order kinetic with the half-lives of 3.4 to 5.2 and 2.4 to 3.0 days, respectively. In addition, we applied the dynamic plant uptake model dynamiCROP and combined it with results from the field experiments to …
Assessment of nitrate contamination risk: The Italian experience
2009
16 páginas, 19 figuras, 10 tablas.-- El PDF es el manuscrito aceptado para su publicación.-- et al.
Occurrence of fumonisins in organic and conventional cereal-based products commercialized in France, Germany and Spain
2013
A fast and effective method for quantitative determination of fumonisins B1 and B2 (FB1 and FB2) in different cereal-based products was developed. Fumonisins were extracted combining a solid liquid extraction (SLE) pre-treatment and immunoaffinity columns (IACs), which were applied for an effective clean-up. Consecutively, high pressure liquid chromatography (HPLC) coupled to hybrid triple quadrupole-linear ion trap mass spectrometer (QTrap®) was used for the separation, detection and quantification of targeted mycotoxins. The analytical method showed acceptable recoveries ranged from 89.7% to 99.1%, as well as a relative standard deviation (%, RSD) lower than 12%. A total of 1250 samples f…
Monoclonal antibody-based immunoassays for cyprodinil residue analysis in QuEChERS-based fruit extracts
2015
Cyprodinil is among the most common agrochemical residues found in highly perishable fruits, such as strawberries. In the present study, high-affinity monoclonal antibodies to this anilinopyrimidine fungicide were raised for the first time with the aim to produce valuable immunochemical analytical assays. Cyprodinil bioconjugates and the generated novel monoclonal antibodies were employed for sensitive competitive immunoassay development in two different formats. The limits of detection of the optimized assays were 20 and 30 ng L-1 for the indirect and direct assay, respectively. Influence over assay parameters of different physicochemical factors was studied. Strawberry samples were extrac…
Determination of pesticide residues in fruit and vegetables.
1996
A review concerning the determination of pesticide residues in fruit and vegetables is presented. The basic principles and recent developments in the extraction and quantitation of pesticides are discussed. Consideration is given to solid phase and supercritical extraction techniques, automation and robotic systems, and immunoassay procedures.
Chemical profiling of the synthetic cannabinoid MDMB-CHMICA: Identification, assessment, and stability study of synthesis-related impurities in seize…
2019
In this work, the most discriminating synthesis-related impurities found in samples from seizures and controlled synthesis of the synthetic cannabinoid MDMB-CHMICA (methyl (S)-2-(1-(cyclohexylmethyl)-1H-indole-3-carboxamido)-3,3-dimethylbutanoate) were characterized. Based on 61 available powder samples of MDMB-CHMICA, 15 key-impurities were assessed, isolated in larger quantities via flash chromatography and structurally elucidated and characterized via high resolution mass spectrometry and nuclear magnetic resonance spectroscopy. Apart from verifying the relation of the impurities to the major component, the interpretation of their chemical structures with distinct structural elements pro…
Comparison of green sample preparation techniques in the analysis of pyrethrins and pyrethroids in baby food by liquid chromatography–tandem mass spe…
2017
A new selective and sensitive liquid chromatography triple quadrupole mass spectrometry method was developed for simultaneous analysis of natural pyrethrins and synthetic pyrethroids residues in baby food. In this study, two sample preparation methods based on ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) and salting-out assisted liquid–liquid extraction (SALLE) were optimized, and then, compared regarding the performance criteria. Appropriate linearity in solvent and matrix-based calibrations, and suitable recoveries (75–120%) and precision (RSD values ≤ 16%) were achieved for selected analytes by any of the sample preparation procedures. Both methods provided the…
Dissipation and distribution of atrazine, simazine, chlorpyrifos, and tetradifon residues in citrus orchard soil.
1997
An environmental fate study was conducted in a citrus orchard plot in Valencia (Spain) in the fall of 1993. Dissipation and distribution of atrazine, simazine, chlorpyrifos and tetradifon residues following their controlled addition for agricultural purposes in a mediterranean red soil (Luvic Calcisol, Rhodoxeralf) were evaluated. During a two-month period, the amounts of applied pesticides in different soil layers (0-0.05, 0.05-0.22, 0.22-0.42, and 0.42-0.52 m) were monitored. In addition, information on soils, weather and agricultural practice were collected. Degradation half-lives were calculated, assuming zero-order kinetics: 11 days for atrazine, 12 days for simazine, 10 days for chlor…
Determination of urea-derived pesticides in fruits and vegetables by solid-phase preconcentration and capillary electrophoresis
2001
A multiresidue analytical method based on solid-phase extraction (SPE) enrichment combined with capillary electrophoresis (CE), using micellar electrokinetic capillary chromatography (MEKC), was developed to determine ten substituted urea pesticides in orange and tomato samples. Several factors such as pH, composition and concentration of the buffer, concentration of surfactant, addition of organic solvent, and working voltage were optimized to obtain the best compound separation in the shortest time. Separation can be achieved in 7 min using a micellar aqueous pH 9 buffer composed of 4 mM borate and 35 mM sodium dodecyl sulfate. After an SPE procedure, which provided a 10-fold enrichment, …