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ABSTRACT: Chlorothalonil is a non-systemic fungicide that is easily degraded in contact with plants and soil or even by the effect of light and pH. A method for the determination of chlorothalonil in courgettes, strawberries, oranges, leeks and tomato by solvent extraction followed by GC-MS/MS with a triple quadrupole analyser was developed. The causes of chlorothalonil degradation during sample treatment were studied and minimised. The final method was based on extraction with acetone in the presence of 0.1 M EDTA sodium salt solution, and clean-up by SPE using OASIS HLB cartridges. Isotope-labelled hexachlorobenzene (HCB-(13)C(6)) was added as an internal standard to the SPE extracts before analysis by GC-MS/MS (EI) (QqQ) analysis in order to correct for instrumental deviations. Quantification was performed by matrix-matched standard calibration using relative responses to the internal standard. Two MS/MS transitions were used for mass spectrometric determination of chlorothalonil to ensure reliable quantification and confirmation. The method was validated using blank samples (for all matrices) spiked at two levels. Recoveries between 77% and 110% and an RSD below 20% were obtained for 0.1 and 0.01 mg kg(-1) spiking levels (n = 5). The validated method was applied to treated and untreated samples collected from an experimental field where a chlorothalonil formulated was applied.
Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment 11/2012;
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ABSTRACT: In this work, the capability of gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF MS) for quantitative analysis of pesticide residues has been evaluated. A multiclass method for rapid screening of pesticides (insecticides, acaricides, herbicides and fungicides) in fruit and vegetable matrices has been developed and validated, including detection, identification and quantification of the analytes. To this aim, several food matrices were selected: high water content (apples, tomatoes and carrots), high acid content (oranges) and high oil content (olives) samples. The well known QuEChERS procedure was applied for extraction of pesticides, and matrix-matched calibration using relative responses versus internal standard was used for quantification. The sample extracts were analyzed by GC-TOF MS. Up to five ions using narrow window (0.02 Da)-extracted ion chromatograms at the expected retention time were monitored using a target processing method. The most abundant ion was used for quantification while the remaining ones were used for confirmation of the analyte identity. Method validation was carried out for 55 analytes in the five sample matrices tested at three concentrations (0.01, 0.05 and 0.5 mg/kg). Most recoveries were between 70% and 120% with relative standard deviations (RSDs) lower than 20% at 0.05 and 0.5mg/kg. At 0.01 mg/kg, roughly half of the pesticides could be satisfactorily validated due to sensitivity limitations of GC-TOF MS, which probably affected the ion ratios used for confirmation of identity. In the case of olive samples, results were not satisfactory due to the high complexity of the matrix. An advantage of TOF MS is the possibility to perform a non-target investigation in the samples by application of a deconvolution software, without any additional injection being required. Accurate-mass full-spectrum acquisition in TOF MS provides useful information for analytes identification, and has made feasible in this work the discovery of non-target imazalil, fluoranthene and pyrene in some of the samples analyzed.
Journal of chromatography. A 05/2012; 1244:168-77. · 4.19 Impact Factor
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ABSTRACT: A multi-residue method has been developed and validated for the simultaneous quantification and confirmation of around 130 multiclass pesticides in orange, nectarine and spinach samples by GC-MS/MS with a triple quadrupole analyzer. Compounds have been selected from different chemical families including insecticides, herbicides, fungicides and acaricides. Three isotopically labeled standards have been used as surrogates in order to improve accurate quantitation. Samples were extracted by using accelerated solvent extraction (ASE) with ethyl acetate. In the case of spinach, an additional clean-up step by gel permeation chromatography was applied. Determination was performed by GC-MS/MS in electron ionization mode acquiring two MS/MS transitions for each analyte. The intensity ratio between quantitation transition (Q) and identification transition (q) was used as confirmatory parameter (Q/q ratio). Accuracy and precision were evaluated by means of recovery experiments in orange, nectarine, and spinach samples spiked at two concentration levels (0.01 and 0.05 mg/kg). Recoveries were, in most cases, between 70% and 120% and RSD were below 20%. The limits of quantification objective for which the method was satisfactorily validated in the three samples matrices were for most pesticides 0.01 mg/kg. Matrix effects over the GC-MS/MS determination were tested by comparison of reference standards in pure solvent with matrix-matched standards of each matrix. Data obtained showed enhancement of signal for the majority of analytes in the three matrices investigated. Consequently, in order to reduce the systematic error due to this effect, quantification was performed using matrix-matched standard calibration curves. The matrix effect study was extended to other food matrices such as raisin, paprika, cabbage, pear, rice, legume, and gherkin, showing in all cases a similar signal enhancement effect.
Analytical and Bioanalytical Chemistry 03/2010; 397(7):2873-91. · 3.78 Impact Factor
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ABSTRACT: The objective of this paper is to investigate the potential of multiple headspace-solid-phase microextraction (MHS-SPME) for the determination of volatile compounds in complex matrix samples. A method based on MHS-SPME for the determination of around 20 volatile compounds, responsible of tomato flavour and aroma has been developed and validated, using gas chromatography with mass spectrometry (ion trap analyser) for analysis. For this purpose, the experimental beta parameter, resulting from the MHS-SPME theoretical development, has been obtained from real sample analysis (in triplicate) for each identified compound, carrying out up to 5 consecutive extractions. Later, this parameter is used to perform quantitation of real samples after just a single HS-SPME extraction. Precision, expressed as repeatability, has been evaluated by analysing six replicates of a real sample, showing relative standard deviations between 4 and 20%. For accuracy study, quantitative results have been compared with those obtained by means of standard additions on replicate samples, and no statistically significant differences between the two methods were observed. Since MHS-SPME uses the estimated total area corresponding to the complete extraction of compounds (obtained from the beta parameter), quantitation can be carried out by external calibration using standards in solvent and splitless injection, instead of by SPME. Linearity, tested in the range 0.05-15 microg/mL, showed satisfactory values, with coefficients of correlation between 0.995 and 0.999. Limits of detection were in the range of 0.25-5 ng/g. MHS-SPME has been proved to be an adequate technique to avoid matrix effects in complex samples quantitation. Its applicability to the determination of volatile tomato components, together with its limitations, is discussed in this article.
Journal of Chromatography 12/2008; 1216(1):127-33. · 4.53 Impact Factor
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ABSTRACT: A simple multi-residue procedure has been developed and applied to the analysis of pesticides in groundwater samples from the Comunidad Valenciana, a predominantly agricultural area on the Mediterranean coast of Spain. The procedure includes a liquid-liquid extraction, after addition of NaCl on the samples, and a subsequent analysis by capillary gas chromatography using a dual detection system with electron capture and nitrogen-phosphorous detectors. This allows the determination of more than 30 compounds (organophosphorous, organochlorine and pyrethroid pesticides) at the low ppb (g l–1) levels. Detection limits obtained varied between 0.01 g l–1 (lindane, fonofos) and 0.5 g l–1 (cypermethrin). An additional injection of the sample extracts into a gas chromatograph equipped with a column of different polarity and electron capture detector is used for the confirmation of chromatographic peaks. The recommended procedure has been applied to 66 ground water samples. Pesticides, including organophosphorus and organochlorine compounds were detected in 31 of them, in levels ranging from 0.02 to 0.7 g l–1.
Chromatographia 08/1993; 37(5):303-312. · 1.20 Impact Factor
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ABSTRACT: A study of different multi-residue methods for the determination of pesticides in groundwater samples was made by comparing several extraction procedures which included liquid-liquid partitioning and solid-phase extraction. The effect of extraction conditions, such as organic solvent, volume ratio, addition of NaCl and pH, were studied. Recoveries, detection and determination limits, as well as precision of the procedures for several replicates were obtained. The pesticides studied were selected taking into account their application on citrus groves in the Plana of Castellon (Spain). These compounds included organochlorine pesticides (lindane, dicofol, chlorfenson and tetradifon), organophosphorous (dimethoate, fenitrothion and methidathion) and phenoxyacid herbicides (MCPA and 2,4-D). Analysis were carried out by high resolution gas chromatography using a dual detection system (ECD and NPD), as well as by high performance liquid chromatography (HPLC) with UV detection. This procedure was applied to several groundwater samples from Castellon province (Spain).
Science of The Total Environment 05/1993; 132(2-3):297-312. · 3.29 Impact Factor
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ABSTRACT: A comparative study of different multiresidue methods for the determination of organochlorine and organophosphorus pesticides in fruit samples has been carried out. Recoveries for each pesticide added to a peach sample were obtained after applying different extraction systems. The study was performed with the following pesticides: dimethoate, chlorpyrifos, fenitrothion, lindane, malathion, methidathion, phentoate and tetradifon. Extraction systems induded: acetonitrile+anhydrous sodium sulphate, acetonitrile-water+Celite acetone and acetone-methanol. Determination of pesticides was performed by gas capillary chromatography with ECD and NPD. GC/FPD and GC/MS were also used for confirmation and identification purposes.
Chromatographia 01/1990; 29(9):459-466. · 1.20 Impact Factor
