Determination Of Several Pesticides Research Articles

Pesticides: Behavior in Agricultural Soil and Plants.

This review considers potential approaches to solve an important problem concerning the impact of applied pesticides of various classes on living organisms, mainly agricultural crops used as food. We used the method of multi-residual determination of several pesticides in agricultural food products with its practical application for estimating pesticides in real products and in model experiments. The distribution of the pesticide between the components of the soil-plant system was studied with a pesticide of the sulfonylureas class, i.e., rimsulfuron. Autoradiography showed that rimsulfuron inhibits the development of plants considered as weeds. Cereals are less susceptible to the effects of pesticides such as acetamiprid, flumetsulam and florasulam, while the development of legume shoots was inhibited with subsequent plant death.

Studies on multiresidue determination of pesticides in fruits and vegetables by gas chromatography/mass spectrometry

A multiresidue method using gas chromatography/mass spectrometry (GC/MS) was evaluated for the determination of several pesticides in fruits and vegetables. The pesticides were extracted using a slightly modified Luke multiresidue procedure, separated by capillary column gas chromatography and detected by mass chromatography with quadrupole mass spectrometer in the electron impact mode. Recovery studies of chlorpyrifos, diazinon, endosulfan, fenarimol, fenvalerate, folpet, iprodione, malathion, methamidophos, phosmet and procymidone were performed at the 0.5 ppm spike level in cherry tomatoes, chin-chian pe-tsai, Chinese cabbages, kidney beans and oranges. Recoveries were between 64.6 and 124.6%, with the exception of methamidophos which produced interference due to the constituents of the samples. Coefficients of variation ranged between 0.3 and 17.6%, with an average of 5.3%. The estimated limits of detection of the pesticides (except methamidophos) in the crops were at the 0.1 ppm level. Because the mass spectrometer is capable of achieving higher levels of molecular specificity as compared to the traditional GC detectors and can be programmed to search for several hundred target ions simultaneously, GC/MS may be a promising method for the use of regulatory agencies with which to monitor pesticide residues in daily food products.

Solid-phase extraction and gas chromatography-tandem mass spectrometry method for the simultaneous determination of several pesticides in water

Contamination of surface and groundwater sources with pesticide residues has been of great concern for a long time and it is a major challenge for the preservation and sustainability of the environment. In order to accomplish the requirements of the European Directive 98/83/EC, we developed and validated an analytical method based on the combination of gas chromatography and tandem quadrupole mass spectrometry (GC-MS/MS) using solid-phase extraction as sample preparation. In this work nine pesticides were studied: molinate, simazine, atrazine, terbuthylazine, diazinon, alachlor, metalaxyl, metolachlor and pendimethalin. In order to get the best sensitivity and selectivity for each pesticide, several parameters of the tandem mass spectrometry were optimized using the MRM mode. Good linearity of the detector response was found for all pesticides at concentrations within the tested working range, with linear determination coefficients higher than 0.9988. Recoveries studies in several matrices with different fortification levels were performed, with recoveries between 77 and 115% with RSD lower than 9.5%. The MQLs obtained for these compounds were between 0.013 microg L(-1) and 0.022 microg L(-1), which were much lower than the maximum level established by the European legislation.

Multiresidue analysis of pesticides in fruits and vegetables by gas chromatography-mass spectrometry

A multiresidue method was assessed for the determination of several pesticides (organochlorine, organophosphorus, pyrethroids, triazole, amidine) using gas chromatography/mass spectrometry. The extraction of pesticides was carried out by liquid-liquid extraction (LLE) and solid-phase extraction (SPE) using two types of columns (CN and C18). The extracts were cleaned by the addition of florisil, the pesticides were separated by capillary column gas chromatography and detected by mass spectrometry in the electron impact mode. The extraction using C18 column provided the best results for most of the analyzed pesticides. The majority of pesticides recoveries from the four fruits and vegetables (apples, pears, tomatoes and pepper) were greater than 60%. Linearity and precision were satisfactory. The estimated limits of detection and limits of quantification ranged from 0.01 to 0.1 mg/kg and from 0.02 to 0.3 mg/kg, respectively. The proposed procedure was found to be useful for the multiresidue analyses of pesticides in agricultural products for routine monitoring programs.

Determination of several pesticides in water by solid-phase extraction, liquid chromatography and electrospray tandem mass spectrometry

The analysis of pesticides in water samples is a problem of primary concern for quality control laboratories due to the toxicity level of these compounds and their public health risk. In order to evaluate the impact of pesticides in the Lisbon drinking water supply system, following the requirements of the European Union Directive 98/83/EC, we developed and validated an analytical method based on the combination of solid-phase extraction with liquid chromatography and tandem mass spectrometry. In this work, several pesticides were studied: imidacloprid, dimethoate, cymoxanil, carbendazime, phosmet, carbofuran, isoproturon, diuron, methidathion, linuron, pyrimethanil, methiocarbe, tebuconazole and chlorpyrifos. Several parameters of the electrospray source were optimized in order to get the best formation conditions of the precursor ion for each pesticide, namely capillary and extractor voltage, cone voltage, cone gas flow rate and desolvation gas flow rate. After optimization of the collision cell energy of the triple quadrupole, two different precursor ion – product ion transitions were selected for each pesticide, one for quantification and one for qualification, and these ions were monitored under time-scheduled multiple reaction monitoring (MRM) conditions. The selection of specific fragment ions for each pesticide guarantees a high degree of selectivity as well as additional sensitivity to quantify trace levels of these pesticides in water samples. This method showed excellent linearity ranges for all pesticides, with correlation coefficients greater than 0.9989. Determination limits (between 0.0041 and 0.0480 μg/L), precision (RSD <9.18%), accuracy and recovery studies in several water samples using solid-phase extraction were also performed.

Multiresidue determination of pesticides in plants by high-performance liquid chromatography following gel permeation chromatographic clean-up

Gel permeation chromatography was applied as a clean-up step in a HPLC multiresidue method for the determination of several pesticides in plants, not amenable to analysis by GC. The pesticides investigated were diflubenzuron, triflumuron, clofentezine, hexythiazox and flufenoxuron. The clean-up technique resulted in a good separation of analytes from co-extractive matrix compounds. Complete HPLC separation of all pesticides was achieved under the conditions selected. The analytical procedure was characterized with high accuracy and precision and acceptable sensitivity to meet requirements for monitoring these pesticides in crops.

Simultaneous determination of several pesticides with chemiluminescent immunoassay on a multi‐spot membrane strip

Chemiluminescent immunoassay with two types of a multispot membrane strip has been developed for the simultaneous determination of several pesticides in water samples. Three types of antibodies with different cross‐reactivity towards s‐triazines were immobilized in three separate spots of the first strip (called a ‘triazine membrane strip') by means of a photoimmobilization technique. The second strip (called a ‘pesticide membrane strip') contained two pesticide‐specific spots with immobilized antibodies, one specific to 2,4‐dichlorophenoxyacetic acid and another with a high extent of cross‐reactivity toward different s‐triazines. Each membrane strip contained two additional spots. One was employed as a positive control or cut‐off spot, and the other one was used to check the background luminescence. The immunoassay with a multispot membrane strip allowed us to estimate semi‐quantitatively the concentration for a particular analyte by a comparison of the recorded light intensities of the analyte spot and the cut‐off spot. The application of the triazine membrane strip provides a differentiation between atrazine, simazine and terbuthylazine in mixtures, and the pesticide membrane strip allows the performance of group‐specific assays.

Enhanced detection sensitivity by large volume injection in reversed-phase micro-high-performance liquid chromatography

High-performance liquid chromatography (HPLC) packed capillary columns have gained a great deal of interest for their role in conjunction with other analytical techniques, particularly mass spectrometry. However, the advantages offered by the low mobile phase flow-rate are often compromised by modest method detection limits due to sub-microliter injection volumes. This is particularly significant with a particle beam interface where the benefits obtained at very low solvent flow-rate (1 μ1) were outlined. In this paper, the effect of large injection volumes (up to 50 μl) on the chromatographic behaviour of a reversed-phase 250 μm I.D. packed capillary column was studied. Due to their differences in chemical properties and to their environmental impact, a selection of basic-neutral and acidic pesticides was found to be appropriate for this investigation. This study was focused on the peculiar sample-column relationship encountered in a micro-HPLC system. Loop shape and matrix composition were found to be the determinant factors for a correct solute displacement into the capillary column. Suitable conditions for the injection of large volumes of trace-level pesticides were described. Previously developed liquid chromatographic-mass spectrometric methods for the determination of several pesticides in water took great advantage from the larger sample availability.

Postcolumn formation of fluorophores from nitrogenous pesticides by UV photolysis

The ultraviolet (UV) photolysis of several classes of nitrogenous pesticides was examined with a view to photo-induced fluorescence detection in flow-injection analysis (FIA) and liquid chromatography. The solvents evaluated as typical reversed-phase mobile phases included water, methanol, and 1:1 mixtures of methanol/water and acetonitrile/water, and methanol/acetonitrilelwater mixtures. Acetone, acetophenone, the surfactant triton X-100, and the photocatalyst titanium dioxide were assessed as photosensitizers to enhance the UV photolysis and fluorescence responses. FIA and liquid chromatographic separations of several pesticides were followed by post-column UV photolysis for the fluorescence detection. Ultraviolet photolysis produces some fluorescent products. The type of photolytic solvent seems to play a significant role. The presence of photosensitizers also affects the fluorescence response of some pesticides. The photochemical transformation products of some of the pesticides are suggested. Analytical figures of merit were evaluated for determination of several pesticides in ground water. The post-column UV photolysis approach for fluorescence detection in liquid chromatography was assessed for several nitrogenous pesticides in ground water samples at ng/g concentrations.

Determination of several pesticides with a chemical ionization ion trap detector

Determination of several pesticides with a chemical ionization ion trap detector

The Thin-Layer Chromatographic Separation of Halogenated Fumigants as Ammonium Halides and Their Subsequent Determination by Meca

Abstract A method is described for the determination of several pesticides containing bromine and chlorine by molecular emission cavity analysis (MECA). The pesticides were decomposed in an oxygen flask and the combustion products dissolved in aqueous ammonia. The ammonium halides were separated by TLC using microcrystalline cellulose adsorbent. After scraping from the TLC plates and dissolving in water the separated components were quantitated by MECA using either the InBr (Λmax = 376 nm) or the InCl (Λmax = 360 nm) emission bands. Recoveries of over 96% were obtained. Soils fortified with l, 2-dibromo-3-chloropropane at levels of 5–25 ppm were extracted using shaking and distillation procedures. Subsequent analysis showed that the shaking extraction gave a recovery of 92% compared to 85% from acid refluxing.

Tissue and fat preparation for pesticide determination by gas chromatography

Portions of previously reported pesticide methods have been uniquely combined to provide a method for the simultaneous determination of several pesticides and their metabolites at low levels in 2-g portions of animal or human tissues. This method, developed for the toxicologist, permits the analysis of a single rat brain for storage and distribution studies and of a human fat biopsy sample for assessment of pesticide exposure. The sample preparation consists of extraction, concentration, and a cleanup by a liquid-solid chromatographic column. Heptachlor epoxide, p, p′-DDE, o, p′-DDT, dieldrin, and p, p′-DDT, in the prepared sample are separated and determined simultaneously by gas chromatography using an electron capture detector. A 5-foot glass column utilizing a silicone liquid phase was operated at 155°C to provide a separation of pesticide residues which were of particular interest in a study of human fats from four geographical areas of the United States. The method, providing quantitative recoveries from tissues, will detect a minimum of 0.01 ppm, p, p′-DDT and even lower concentrations of other pesticides.