Determinación de residuos de fipronil en miel y polen por cromatografía de gases

This work describes the development of the analytical methodology for determining fipronil residues in honey and pollen samples by gas chromatography with two detecting systems: electron-capture detection (GC-ECD) and mass spectrometry (GC-MS). Fipronil was extracted from honey samples by solid-phase extraction, using alumina as adsorbent and hexane-ethyl acetate (1:1, v/v) as eluting solvent, and from pollen samples by matrix solid-phase dispersion with C18 and acetonitrile, assisted by sonication. The developed methods gave recovery results >90% with relative standard deviationsEste trabajo describe el desarrollo de la metodología analítica para determinar residuos de fipronil en muestras de miel y polen por cromatografía de gases con dos sistemas de detección: espectrometría de masas (GC-MS) y detector de captura de electrones (GC-ECD). El pesticida fipronil se extrajo de las muestras de miel mediante extracción en fase sólida, con alúmina como adsorbente y hexano-acetato de etilo (1:1, v/v) como disolvente de elución, y de las muestras de polen por medio de la dispersión de la matriz en fase sólida, C18, y extracción en baño de ultrasonidos con acetonitrilo. Los métodos desarrollados dieron recuperaciones >90% con desviaciones estándar relativa

Analysis of pesticide residues in fruit juices by matrix-solid phase dispersion and gas chromatographic determination

A rapid multiresidue method has been developed for the analysis of pesticides in fruit juices. The compounds studied were two insecticides (endosulfan I, endosulfan II and their metabolite endosulfan sulfate), five fungicides (chlorothalonil, vinclozolin, procymidone, hexaconazole and fenarimol) and two acaricides (dicofol and tetradifon). The method is based on the dispersion of fruit juices on the adsorbent, Florisil, placed in small glass columns, and subsequent extraction of pesticides using a small volume of ethyl acetate. Residue levels were determined by gas chromatography with electron-capture detection. The ECD response for all pesticides was linear in the range of concentrations studied, with correlation coefficients higher than 0.99. Recoveries obtained for pesticides in different fruit juices at various fortification levels were higher than 74%, with relative standard deviations between 1 and 12%. The detection limits ranged from 1 to 5 μg kg-1. The identity of the pesticides was confirmed by GC-MS

Multiresidue determination in soil of pesticides used in tomato crops by sonication-assisted extraction in small columns and gas chromatography

Various herbicides and insecticides belonging to different chemical groups and used in tomato crops were determined in soil. The proposed analytical method was based on the sonication-assisted extraction in small columns (SAESC) of pesticides using ethyl acetate. All pesticides were determined by capillary gas chromatography with electron-capture detection (GC-ECD) and their identity was confirmed by gas chromatography coupled with mass spectrometry (GC-MS). Recoveries obtained for all compounds in the two soils studied varied from 81 to 106% with a relative standard deviation between 2 and 9%. The limit of detection in the conditions assayed was at least 0.01 μg/g for all compounds. The developed procedure was applied to the analysis of real samples, obtained after tomato harvest, from 18 commercial fields in Spain, and residue levels of pendimethalin (0.018-0.650 μg/g) endosulfan-I (0.011-0.032 μg/g), endosulfan-11 (0.014-0.178 μg/g) and endosulfan-sulfate (0.010-0.135 μg/g) were found

Multiresidue analysis of carbamate pesticides in soil by sonication-assisted extraction in small columns and liquid chromatography

A rapid multiresidue method has been developed for the analysis of carbamate insecticides (oxamyl, methomyl, propoxur, carbofuran, carbaryl and methiocarb) in soil. The method is based on the sonication-assisted extraction of soil samples placed in small columns using a low volume of methanol. Residue levels in soil were determined by reversed-phase high-performance liquid chromatography with fluorescence detection after post-column derivatisation. The separation of carbamates is performed on a C8 column with water-methanol as mobile phase. Recovery studies were carried out at 0.5, 0.1 and 0.01 μg/g fortification levels and average recoveries obtained for carbamates ranged from 82 to 99% with relative standard deviations between 0.4 and 10%. The effect of residue residence time and soil moisture content on the insecticide recovery was also studied. The method is linear over the range assayed, from 0.1 to 1 μg/ml. The detection limit for the carbamates varied from 1.6 to 3.7 μg/kg and the quantification limit obtained was 10 μg/kg. The emission and excitation spectra allowed the confirmation of residues at levels around 0.1 μg/g. © 2003 Elsevier B.V. All rights reserved

Influence of the laboratory incubation method on chlorotoluron and terbutryn degradation in soil

Degradation of the herbicides chlorotoluron and terbutryn was assayed using three different incubation systems columns of undisturbed soil, columns packed with sieved soil, and flasks. Two different soils were employed, a sandy loam (A) and a loam soil (B), and different temperature (4-32 °C) and moisture content (7-13%) conditions were assayed. Dissipation of both herbicides in soil A for treatment T2 (25 °C and 10% of moisture content) was significantly different in the three different incubation systems assayed. In the case of soil B, with lower organic matter content, the obtained half-lives for treatment T2 were statistically indistinguishable in all the incubation systems, with the exception of the flask incubation of terbutryn. Incubation in packed cores generally yielded longer half-lives than flask incubations in all the other treatments for both soils and both compounds. Differences among incubation systems were greater with terbutryn than with chlorotoluron, which has a lower sorption coefficient

Determination of corn herbicides by GC‒MS and GC-NPD in environmental samples

Several herbicides widely used to control weeds in corn, atrazine, alachlor, metolachlor, and pendimethalin, have been determined in soil and water. Analysis of herbicides was performed by GC-NPD and GC‒MS. Soil was extracted with ethyl acetate on a mechanical shaker, and water was extracted with dichloromethane in a separatory funnel. The average recoveries through the method were higher than 90% in soil and 85% in water. The detection limit was lower than 0.01 ppm in soil and 0.1 ppb in water for GC‒MS and GC-NPD, respectively. Soil samples from corn fields, after harvest, were taken from the surface (0‒10 cm) of several fields located in Albacete and Guadalajara, Spain, and water was taken from wells located in the fields. These samples were analyzed according to the proposed GC methods, and statistically similar values between the two methods were obtained. The identities of the detected herbicides were confirmed by GC‒MS. © 1994, American Chemical Society. All rights reserved

Multiresidue analysis of insecticides in soil by gas chromatography with electron-capture detection and confirmation by gas chromatography-mass spectrometry

A rapid multiresidue method has been developed for the analysis of nine insecticides (organochlorines, pyrethroids and organophosphorus) in soil. The method is based on the sonication extraction of residues from a certain amount of soil placed in a small column, using ethyl acetate. The effect of the residence time of insecticides in soil, the material of the columns used (glass or plastic columns) and the soil moisture content on the recovery of these compounds was also studied. Residues were determined by gas chromatography with electron-capture detection. The average recovery through the method obtained for these compounds varied from 90 to 108% with a relative standard deviation between 1 and 11%. The results of this study pointed out that the recoveries of insecticide residues obtained with plastic or glass columns at different soil moisture content were similar and that the residence of these compounds in soil during several days did not affect their recovery from soil. Confirmation of residue identity was performed by gas chromatography coupled with mass spectrometry. © 2001 Elsevier Science B.V

Determination of phenoxy ester herbicides by gas and high-performance liquid chromatography

The determination of phenoxy ester herbicides was carried out by high-performance liquid (HPLC) and gas chromatography (GC) and their identification by GC-MS spectrometry. Standards of herbicide esters were obtained from the appropriate acid and a suitable alcohol, mainly 2-butoxyethyl, isooctyl or isobutyl alcohol, using acetyl chloride as a catalyst. The mixture was heated at 100°C for 1 h, after cooling 2 ml of acetate buffer (pH 4.6) were added and then the mixture was diluted to volume with methanol. Good ester conversion (>95%) was achieved. The phenoxy esters were analysed by reversed-phase HPLC on a Spherisorb ODS-2 (5-μm) column with acetonitrile-water (8515) as mobile phase at a flow-rate of 1 ml/min and UV detection at 280 nm. GC was performed on a BP-5 capillary column with helium as carrier gas (10 ml/min) and flame ionization detection. Esters were identified by GC-ion trap detection on a BP-1 capillary column. Several mixtures of phenoxy ester herbicides in formulations were analysed using the proposed methods and good agreement between the HPLC and GC results was obtained. © 1991