Determination Of Dimethoate Research Articles

Development of New Kinetic‐Spectrophotometric Method for Determination Insecticide Dimethoate in Milk and Water

AbstractIn the present study, a new sensitive and simple kinetic‐spectrophotometric method for the determination of the insecticide dimethoate[O,O‐dimethyl‐S‐(N‐methyl‐carbomoylmethyl)‐phosphoro‐dithioate] is developed. The method is based on the inhibited effect of dimethoate on the oxidation of sulphanilic acid (SA) by potassium periodate in acetate buffer in presence Fe(III) ion and 1,10‐phenantroline. Dimethoate was determined with linear calibration graph in the interval from 28.10 to 196.70 ng/mL. The optimized conditions yielded a theoretical detection limit of 21.64 ng/mL based on the 3Sb criterion. The RSD is 4.85‐1.2% for the concentration interval of dimethoate 28.10‐196.70 ng/mL. The reaction was followed spectrophotometrically at 368 nm. The kinetic parameters of the reaction are reported, and the rate equations are suggested. The developed procedure was successfully applied to the rapid determination of dimethoate in spiked milk and water samples. Liquid‐liquid extraction and solid‐phase extraction (SPE) was used for extraction of dimethoate from milk and water samples with Chromabond® (Macherey‐Nagel) C18 cartridges. The HPLC method was used like an comparative method to verify the results. The results obtained by two different methods showed good agreement.

Determination of dimethoate, 2,4-dichlorophenoxy acetic acid, mecoprop and linuron pesticides in environmental waters in Republic of Macedonia by high performance liquid chromatography

An HPLC-UVDAD method for determination of dimethoate, 2,4-dichlorophenoxy acetic acid (2,4-D), mecoprop (MCPP) and linuron in environmental waters was developed. The water samples were concentrated and extracted by a solid phase extraction (SPE) method on Bond Elut PPL cartridges. After extraction the investigated compounds were separated on Stability RP Pesticides chromatographic column using mobile phase composed of acetonitrile- water-acetic acid in volume fractions of 39:59:2 and flow rate of 0.7 mL/min. Ultraviolet absorption detection was carried out for dimethoate, 2,4-D and MCPP at 229 nm, and for linuron at 249 nm. Recoveries made from 500 mL of drinking waters using solid phase extraction ranged between 64.3–92.1 %. The method was applied to environmental waters in Macedonia that receive runoffs from agriculture lands. The levels of pesticides under study ranged between 0.31 μg/L and 7.05 μg/L, depending on the compound and sampling period.

Determination of Dimethoate in Olive Oil by Adsorptive Stripping Square‐Wave Voltammetry

AbstractA method for the determination of dimethoate in olive oil by adsorptive stripping square‐wave voltammetry has been developed on the base that this pesticide is hydrolyzed in basic media giving rise to an adsorptive‐reductive peak at −0.780 V. Extraction of dimethoate from olive oil with ethanol‐water and posterior clean‐up with C18 cartridges is carried out. Response Surface Methodology has been used for the optimization of the extraction procedure. A matrix effect is observed in olive oil extract; therefore the standard addition method must be used. The detection limit is 19.00 ng g−1 and recoveries for three levels of fortification are ranged from 79.9% to 104.5%.

Solid‐phase microextraction for gas chromatographic/mass spectrometric analysis of dimethoate in human biological samples

A new, simple and rapid procedure for the determination of dimethoate in urine and blood samples was developed using direct immersion solid-phase microextraction and gas chromatography/mass spectrometry. This technique required only 0.1 mL of sample, and ethion was used as internal standard. Two types of coated fibre were compared (100 microm polydimethylsiloxane, and 65 microm Carbowax/divinylbenzene). Other parameters, such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH, were optimized to enhance the sensitivity of the method. Limits of detection (LODs) and quantitation (LOQs) were 50 and 100 ng/mL for urine and 200 and 500 ng/mL for blood, respectively. The method was found to be linear between the LOQ and 40 microg/mL for urine, and between the LOQ and 50 microg/mL for blood, with correlation coefficients ranging from 0.9923-0.9996. Precision (intra- and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries of dimethoate were 1.24 and 0.50% for urine and blood, respectively. Because of its simplicity and the fact that small volumes of sample are used, the described method can be successfully used in the diagnosis of poisoning by this pesticide, namely in those situations where the sample volume is limited, as frequently occurs in forensic toxicology.

Extractive Spectrophotometric determination of Dimethoate in Environmental Samples with Azure‐B

A new simple and selective spectrophotometric method is developed for the determination of dimethoate by using Azure‐B is described. The method was based on the alkaline hydrolysis of dimethoate in presence of sodium ethoxide to form sodium dimethyl dithiophosphate (Na‐DMDTP). The Na‐DMDTP was formed as an ion‐pair complex with cationic dye, azure‐B. The ion‐pair complex was extracted into chloroform. The color of the organic layer was measured at 535 nm. The method was applied to the determination of dimethoate residues in water, grain and soil samples.

Rapid GC-FPD determination of organophosphorus pesticide residues in Sicilian and Apulian olive oil

A simple and quick method for the determination of dimethoate, parathion-methyl, fenthion, parathion-ethyl, and methidathion in olive oil is described. Analysis was carried out using GC (capillary column 5 m × 0.32 mm × 0.45 μm) with aspecific detector (FPD), after sample extraction with acetonitrile. No cleanup was necessary because there were no interferences in the chromatogram. Recoveries of five pesticides at three fortification levels (1.0, 0.2 and 0.05 mg/kg) were in the range 78–97%. Seventy-nine samples were collected from Sicilian and Apulian individual growers during 2002–2003. Only 16% of the samples contained fenthion in concentrations ranging from 0.09 to 0.73 mg/kg; no other pesticides were detected in the 79 samples.

Solid‐Phase Extraction for the Determination of Dimethoate in Environmental Water and Soil Samples by Micellar Electrokinetic Capillary Chromatography (MEKC)

A micellar electrokinetic chromatography (MEKC) procedure has been developed for the analysis of dimethoate (DM) in environmental water and soil samples, using solid phase extraction (SPE) as a clean‐up and pre‐concentration technique to improve selectivity and DM detection limits. The limit of quantification (LOQ) was 1 µg/mL for direct injection and 3 ng/mL after the SPE pre‐concentration procedure. Within‐run and between‐day reproducibility studies performed at 0.02, 0.05, and 0.2 µg/mL indicated that the procedure was indeed reproducible. Quantification was by UV detection at 200 nm. The capillary electrophoresis (CE) method proposed uses sodium borate 100 mM with sodium dodecyl sulfate 50 mM, pH 8.4 as a buffer. The method was simple and fast, with good recoveries, which on average ranged from 82 to 92% with a relative standard deviation of 7% or less for water and soil samples fortified at 10, 20, 30, and 300 ng/mL. Our results show CE to be a powerful analytical tool for the determination of DM in environmental water and soil samples.

Selective Determination of Dimethoate Using Ion Mobility Spectrometry with Single and Mixed Alternate Reagent Ions

Dimethoate, one of the organophosphorus pesticides, was selectively determined by ion mobility spectrometry (IMS) along with the single and mixed alternate reagent ions. By doping ammonium, acetone, ethanol, ether, and methanol into the carrier gas, the best selective detection was obtained by the addition of ammonium having the highest proton affinity among these single alternate reagent ions. Three mixed alternate reagents including ammonium−acetone, ammonium−ether, and acetone−ether, which were also used to improve the selectivity, showed better results than that single-solvent dopants gained. The best resolution and the highest abundance of the dimethoate peak were observed in its IMS spectrum after the addition of the mixed ammonium−acetone among all the above-mentioned dopants. The relationship curves for the concentration of ammonium and mixed ammonium−acetone to the response of dimethoate were studied. Ammonium at ∼1.0 μg/L levels or 1.0 μg/L ammonium at plus acetone at ∼1.0 μg/L levels exhibited the strongest response of dimethoate. In addition, the direct determination of dimethoate residues was compared to its selective detection with mixed ammonium−acetone as the alternate reagent ions in a field test. A model for the selective analysis of an analyte having middle proton affinity in mixed compounds is proposed.

Determination of dimethoate and fenitrothion in estuarine samples by C-18 solid-phase extraction and high-resolution gas-chromatography with nitrogen-phosphorus detection

Dimethoate [S-((2-(methylamino)ethyl)-2-oxoethyl)phosphorodithioate] and fenitrothion [O,O-dimethyl O-(4-nitro- m-tolyl)phosphorothioate], both organophosphorus pesticides (OPs), have been successfully enriched on monofunctional C-18 solid-phase extraction (SPE) cartridges and quantified by high-resolution capillary gas-chromatography with nitrogen-phosphorus detection (GC-NPD). The method was optimised for estuarine conditions. The recoveries varied significantly with the pH values of spiked seawater samples in the range pH 6.5–9.0 for both compounds. Salinity did not affect the recoveries of fenitrothion whereas the recoveries of dimethoate increased with salinity. The highest recoveries from water samples spiked at trace concentrations of 100 ng l −1 were 68% and 91% for dimethoate and fenitrothion, respectively, and were achieved at pH 6.5 and a salinity of 36‰. Recoveries from ultrasonically extracted sediments, spiked at 100 ng g −1 dry weight were 91% for dimethoate and 86% for fenitrothion. The detection limits ( s n = 3 ) for dimethoate and fenitrothion in water and sediment samples were 1 ng l −1 and 2 ng g −1 dry weight, respectively. The reproducibility (RSD) of all determinations was < 10%. Comparison of the GC-EI-MS spectra showed that ions m z 87,93 and 229 for dimethoate and m z 109, 260 277 for fenitrothion are suitable for selective ion monitoring. The method was not suitable for extraction and quantification of dimethoxon, an oxygen analogue of dimethoate, as the recoveries were always below 20%. GC column lifetime was significantly improved after calibrations were performed with standard solutions prepared in OP-free extracts of natural samples.

Determination of dimethoate in water by cathodic stripping square‐wave voltammetry

AbstractThis article describes the direct‐determination of the pesticide dimethoate In river water in an alkalin media and accumulaton medium through cathodic stripping voltammetry. By employing an alkaline potential of 30 mV, reduction peak appears at −0.7 V. The detection limit is 1 ng ml−1.

Extractive spectrophotometric determination of dimethoate with molybdate and Methylene Blue by a flotation–dissolution method

A sensitive extraction spectrophotometric method based on flotation–dissolution is described for the determination of trace levels of the organophosphorus pesticide dimethoate. Dimethoate is converted into a molybdophospho complex by reaction with ammonium molybdate in sulfuric acid medium. The complex floating on the interface of the aqueous and organic layers along with Methylene Blue as an ion associate is separated and dissolved in acetone. The colour system obeys Beer's law in the range 0.02–0.16 µg ml–1 of dimethoate. The molar absorptivities of the system calculated in terms of phosphorus and dimethoate are 1.5 × 105(±100) l mol–1 cm–1 and 1.08 × 106(±100) l mol–1 cm–1, respectively. The standard deviation and relative standard deviation were 0.006 µg ml–1 and 3.2%, respectively. The method was satisfactorily applied to the determination of dimethoate in water, soil and plant materials.

PESTICIDE RESIDUES ON FRESH AND PROCESSED VEGETABLES

A research project was undertaken in 1990 with the objective of improving both quality and productivity of peas, beans and sweet corn grown and processed in Quebec (Canada). It was conducted with the technical and financial help of five proccessing companies. Cultivar trials were undertaken as part of this project together with an evaluation of commercial practices in the areas of pest control, fertilization and crop management. Samples of fresh and processed products were analysed for nutritional quality and pesticide residues. During this presentation we will show preliminary results of the pesticide residue analyses and will compare fresh and processed products. So far, determination of dimethoate, trifluralin and bentazone (peas), azinphosmethyl and permetrin (beans) and cypermetrin (sweet corn) showed no concentration exceeding the Canadian norm (&lt;0, 1mg/kg), with the exception of a bean field with azinphosmethyl residues. Canning and freezing operations greatly reduced pesticide residues so that all processed samples tested below detectable levels.

Determination of dimethoate in blood and hemoperfusion cartridge following ingestion of formothion: A case study

A 57-year-old male who had ingested not more than 22 g of formothion was semicomatose on admission to hospital, approximately 1.5 h after ingestion. Dimethoate, a hydrolyzed formothion, was found in blood samples collected from the patient and in the charcoal column in the direct hemoperfusion cartridge which was used 6 to 7.5 h after ingestion. It was extracted and purified by Extrelut ® column extraction. A gas chromatograph, equipped with a flame photometric detector and a gas chromatograph-mass spectrometer, were used to detect and confirm the presence of dimethoate. The blood dimethoate concentrations which were taken approximately 1.5 and 6 h after ingestion were 21.4 and 12.7 μg/g, respectively. A blood dimethoate concentration of 21.4 μg/g would appear to indicate a high level of formothion intoxication. The total amount of dimethoate found in the charcoal column used was 15 mg.

Determination of Dimethoate in Human Blood by Impregnated Silica Plates and Gas Chromatography

Abstract A method for the determination of Dimethoate in human blood is presented here. After extraction with acetone-hexane (1+9V/V) dimethoate is separated on p-cresol impregnated thin silica plates as well as by Gas Chromatography using nitrogen phosphorous detector. The recovery of dimethoate added to human blood was quite satisfactory.

Determination of Dimethoate in Waste Water, Soil and Sediment Using Gel Permeation Chromatography for Sample Clean-up

Abstract A method for the determination of trace amounts of the organophosphorus insecticide dimethoate in waste water, soil and sediment is presented. Sediment and soil samples are extracted by soxhelt with acetone/hexane followed by partition of the extract between methylene chloride and water. Separation of dimethoate from other compounds is carried out using gel permeation chromatography with Bio-Beads SX-3. Dimethoate is determined by capillary gas chromatography with a nitrogen-phosphorus detector. Detection limits are 10, 30 and 130ppt for surface water, waste water and soil/sediment respectively. Recoveries are 70.6–75.2% with standard deviations between 5.4 and 9.2%.

Thin Layer Chromatography and in situ Fluorometry for the Quantitative Determination of Dimethoate and Malathion in Lettuce

Abstract Dimethoate and malathion in spiked lettuce extracts are separated by thin layer chromatography on silica gel followed by in situ fluorometric determination. Fluorescence is produced by spraying the developed chromatogram with a palladium chloride-calcein reagent. A ligand exchange occurs in which the palladium complexes preferentially with the sulfur in the pesticide, releasing the metal-fluorochromic indicator calcein. For dimethoate, a linear response is obtained for 10—100 ng/spot and the need for a preliminary cleanup procedure is eliminated.

Gas-Liquid Chromatographic Method for the Determination of Dimethoate and Dimethoxon Residues in Plant and Animal Tissues, Milk, and Eggs

Abstract Residues of both dimethoate and dimethoxon are extracted from finely chopped plant or animal tissues with methylene chloride. The resulting extract is concentrated and cleaned up by silica gel chromatography, if necessary. The concentrate is injected into a gas chromatograph equipped with either a flame photometric or an alkali flame ionization detector and a column containing 11% DC-200 on 60–80 mesh Gas-Chrom Q/0.01% Versamid 900. Recovery values for dimethoate and dimethoxon added a t 0.002–1.0 p pm ranged from 56 to 112% with an overall average of 89.2% for dimethoate and from 60 to 127% with an overall average of 81.9% for dimethoxon. The lower limit at which recovery values were obtained for both compounds was 0.05 p pm for plant tissues, 0.02 for animal tissues and eggs, and 0.002 for milk. Residue values obtained for animal tissues involving both exposure and feeding studies a n d for field-treated plant samples are also presented.

2,6-Dibromobenzoequinone-4-chloroimide as a reagent for determination of dimethoate, monoalkyl-aryl-phosphorothionates and some organic sulfides

2,6-Dibromobenzoequinone-4-chloroimide as a reagent for determination of dimethoate, monoalkyl-aryl-phosphorothionates and some organic sulfides

Rapid determination of Dimethoate in some formulations by infrared spectrophotometry

Rapid determination of Dimethoate in some formulations by infrared spectrophotometry