Analysis Of Organophosphorus Pesticides Research Articles

MISPE Combined with GCMS for Analysis of Organophosphorus Pesticides from Environmental Water Sample

In the present work, a GCMS method coupled with Molecular imprinting technique was developed for the simultaneous determination of five organophosphorus pesticide residues (i.e., diazinon, malathion, phosphamidon, isofenphos-methyl and quinalphos) in environmental water. In order to obtain a highly selective recognition of OPPs, we synthesized molecularly imprinted polymers (MIPs) using malathion as the template, methacrylic acid as the monomer and ethylene glycol dimethacrylate as the crosslinker. After polymerization, molecularly imprinted solid-phase extraction (MISPE) was used for the selective preconcentration of OPPs. The specificity of MIPs and non-imprinted polymers were investigated. The use of MISPE improved the accuracy and precision of the GCMS method. The recoveries of OPPs extracted from water sample at a 1μg/mL spike level were in the range of 82%~97%. The results showed that MIPs enable the selective extraction of OPPs successfully from water sample, and demonstrated the potential of MISPE for selective and cost-effective sample pretreatment.

Stability Monitoring of Pesticide Residues in a Chinese Cabbage Certified Reference Material

Certified reference materials (CRMs) with values traceable to the International System of Units (SI) play a key role for harmonization of measurement results among laboratories. CRMs can be used for validation/verification of analytical methods employed in individual laboratories and for quality assurance or testing proficiency of laboratories. 1-3 Therefore, national metrology institutes (NMIs) of developed countries have been producing CRMs of various types, which are similar to samples to be analyzed, in respect to matrix types, analytes, and their concentrations. Our laboratory, as the NMI of Korea, also has been developing CRMs for environmental, food, clinical, and material analysis. Unfortunately, (potential) users often face a problem that CRMs matching to their samples are not available. In the organic analysis field, the problem is, in most of case, due to instability of target analytes in CRMs as many organic compounds of interest are air-sensitive, light-sensitive, degrading thermally or in acidic or akalic environment, and/or evaporating out of matrix during long-term storage. 4, 5 Therefore, ensuring stability is a key factor for successful production of CRMs for organic analysis. Obtaining reliable analytical results for pesticide residues in foods and agricultural products is a very important issue for food safety. However, it is well known that measurement results of pesticides, in many cases, show a strong dependence on extraction methods and sample clean-up methods employed for the analysis. 6-9 In this respect, using appropriate CRMs is a secure way for a laboratory to ensure the quality of its measurement results through internal verification of its analytical procedures. However, availability of suitable matrix specific CRMs containing relevant pesticides are limited. Those limited number of CRMs available from NMIs world wide are mostly for the analysis of organochlorine pesticides in food samples as those compounds have been known to be relatively stable compared to other types of pesticides. 10,11 As the agricultural use of most organochlorine pesticides was prohibited internationally, current food safety issues are focused on organophosphorus pesticides, carbamates, and pyrethroids, and the need of food CRMs for the analysis of those pesticides has been increasing. However, the inherent instability of those pesticides in food matrices has been an obstacle for developing relevant CRMs. 4 At the beginning of this study, no food CRMs for the analysis of those pesticides was available, up to our knowledge. Therefore, our laboratory started a project to develop food CRMs for the analysis of organophosphorus pesticides, with anticipation to understand and overcome technical difficulties for ensuring stability of those pesticides in food matrix. We prepared a batch of a candidate CRM for the analysis of pesticide residues in Chinese cabbage. Chinese cabbage was chosen as it represents commonly consumed leafy vegetables in Korea. Target analytes were two organophosphorus pesticides (diazinon and chlorpyrifos) and two organochlorine pesticides (α- and β-endosulfans). The two organochlorine pesticides are occasionally detected above regulatory limits from vegetables produced in or imported into Korea though the agricultural use of those pesticides is prohibited. Diazinon was chosen as it is one of the most volatile organophosphorus pesticides and it is expected that its volatility may cause instability in the CRM. After initial certification of the material, its stability in various storage temperatures was monitored for three years to test whether the candidate CRM has adequate long-term stability at shelf storage condition and short-term stability at conditions for transportation to and conventional handling at users’ sites. In this paper, we report the stability test results of the four pesticides in the CRM.

Development of dispersive liquid–liquid microextraction method for the analysis of organophosphorus pesticides in tea

In this article, a new method for the determination of organophosphorus pesticides (OPPs) in tea was developed by using dispersive liquid–liquid microextraction (DLLME) and gas chromatography–flame photometric detection (GC-FPD). A mixture of acetonitrile and n-hexane was used as an extraction solvent for the extraction of OPPs from tea samples. When the extraction process was finished, the mixture of solvents was rapidly dispersed in water; target analyte was extracted to a small volume of n-hexane, using DLLME. Recovery tests were performed for concentration 5.0 μg/kg. The recovery for each target analyte was in the range between 83.3 and 117.4%. The repeatability of the proposed method, expressed as relative standard deviation, varied between 3 and 7.8% ( n = 3). The detection limit of the method for tea was found ranging from 0.030 to 1 μg/kg for all the target pesticides. Compared with the conventional sample preparation method, the proposed method has the advantage of being quick and easy to operate, and has high-enrichment factors and low consumption of organic solvent.

Multiresidue Analysis of 102 Organophosphorus Pesticides in Produce at Parts-per-Billion Levels Using a Modified QuEChERS Method and Gas Chromatography with Pulsed Flame Photometric Detection

A multiresidue method for the analysis of organophosphorus pesticides in fresh produce at levels down to 1.0 microg/kg (ppb) has been developed using a modification of the QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. The procedure entails extraction of pesticides from the sample with acetonitrile, salting-out with magnesium sulfate (MgSO4) and sodium chloride, and cleanup of the resulting extracts with dispersive solid-phase extraction using primary-secondary amine, graphitized carbon black, and MgSO4. Fortification studies were performed for 102 organophosphorus pesticides at 1.0, 10, and 100 ppb in 4 different pesticide-free commodities (grape, orange, spinach, and tomato). Recoveries ranged from 63-125%, with >80% being achieved for most of the pesticides tested in each commodity. The procedure was applied to the analysis of 400 produce samples collected from a cohort of children that participated in the Children's Pesticide Exposure Study and the Longitudinal Dietary Pesticide Exposure Study in which selected 24 h duplicate food items were collected throughout a 12-month period. Residues of 15 of the 102 pesticides were detected at levels ranging from <1 to 526 ppb.

Application of continual injection liquid‐phase microextraction method coupled with liquid chromatography to the analysis of organophosphorus pesticides

A liquid-phase microextraction coupled with LC method has been developed for the determination of organophosphorus pesticides (methidation, quinalphos and profenofos) in drinking water samples. In this method, a small amount (3 microL) of isooctane as the acceptor phase was introduced continually to fill-up the channel of a 1.5 cm polypropylene hollow fiber using a microsyringe while the hollow fiber was immersed in an aqueous donor solution. A portion of the acceptor phase (ca. 0.4 microL) was first introduced into the hollow fiber and additional amounts (ca. 0.2 microL) of the acceptor phase were introduced to replenish at intervals of 3 min until set end of extraction (40 min). After extraction, the acceptor phase was withdrawn and transferred into a 2 mL vial for a drying step prior to injection into a LC system. Parameters that affect the extraction efficiency were studied including the organic solvent, length of fiber, volume of acceptor and donor phase, stirring rate, extraction time, and effect of salting out. The proposed method provided good enrichment factors of up to 189.50, with RSD ranging from 0.10 to 0.29%, analyte recoveries of over 79.80% and good linearity ranging from 10.0 to 1.25 mg/L. The LOD ranged from 2.86 to 82.66 microg/L. This method was applied successfully to the determination of organophosphorus pesticides in selected drinking water samples.

Determination of Organophosphorus Pesticides in Leeks (Allium porrum L.) by GC-FPD

A method was validated for the analysis of organophosphorus pesticides in leeks. The leek sample was cut into about 2 cm lengths and heated in a microwave oven for 50 s to inactivate enzymes. The sample was extracted with 50 mL acetonitrile using an Ultra-turrax T18 blender and cleaned up by solid phase extraction. The target analytes were determined by GC with a flame photometric detector. Average recoveries were 73–118% and limits of detection ranged from 1.1 to 10.0 μg kg−1. The uncertainty of the analysis for each pesticide was evaluated as below 16%. The method was applied to determine organophosphorus pesticides in real samples. The GC–MS was used as confirmatory tool for positive samples.

Evaluation of working air quality by using semipermeable membrane devices: Analysis of organophosphorus pesticides

It has been evaluated the use of semipermeable membrane devices (SPMDs) as passive samplers of organophosphorus pesticides from air, in order to determine the contamination of working environments. Additionally, the use of SPMDs as portable samplers has been also considered. The analytical methodology for the determination of diazinon, chlorpyrifos-methyl, pirimiphos-methyl, chlorpyrifos and fenthion in SPMDs exposed to contaminated air was based on microwave-assisted extraction and gas chromatography with mass spectrometry determination. Limit of detection (LOD) values from 2 to 4 ng SPMD −1 and repeatability from 2 to 7% were obtained by using the aforementioned methodology. Theoretical calculated sampling rates were employed for the estimation of the pesticide concentration in air, by using the pesticide mass retained in the deployed SPMD. The obtained LOD values, for a sampling time of 7 days, were from 1 to 2 ng m −3. The evaluation of the air quality of a pesticide laboratory with an intensive use of diazinon and chlorpyrifos has been made in order to check the operation safety conditions.

Application of dispersive liquid–liquid microextraction for the analysis of organophosphorus pesticides in watermelon and cucumber

In this article, a new method for the determination of organophosphorus pesticides (OPPs) in cucumber and watermelon was developed by using dispersive liquid–liquid microextraction (DLLME) and gas chromatography–flame photometric detection (GC-FPD). Acetonitrile (MeCN) was used as extraction solvent for the extraction of OPPs from plant samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the MeCN extract to another small volume of organic solvent, chlorobenzene, using DLLME. Recovery tests were performed for concentrations between 0.5 and 20 μg/kg; recoveries for each target analyte were in the range between 67 and 111%. The repeatability of the proposed method, expressed as relative standard deviation, varied between 2 and 9% ( n = 3). Limits of detection of the method for watermelon and cucumber were found ranging from 0.010 to 0.190 μg/kg for all the target pesticides. Compared with the conventional sample preparation method, the proposed method has the advantage of being quick and easy to operate, and having high-enrichment factors and low consumption of organic solvent.

Matrix interference and suitability evaluation with multi-residue analysis of organophosphorus pesticides in vegetables

Matrix interference and suitability evaluation with multi-residue analysis of organophosphorus pesticides in vegetables

Application of ceramic/carbon composite as a novel coating for solid-phase microextraction

A ceramic/carbon composite was developed and applied as a novel coating for solid-phase microextraction (SPME). The ceramic/carbon coating exhibited several good properties for SPME, such as high extraction quantities and enhanced thermal and organic solvent stability. Under scanning electron microscopy (SEM), the tightly attached coating layer on stainless steel wire revealed excellent mechanical characteristics. Single fiber and fiber-to-fiber reproducibility were less than 6.9 and 9.5%, respectively. The effects of extraction and desorption parameters such as extraction time, stirring rate, ionic strength, and desorption temperature and desorption time on the extraction/desorption efficiency were investigated and optimized. Coupled to gas chromatography with a flame thermionic detector, the optimized SPME method was applied to the analysis of organophosphorus pesticides (OPPs) in aqueous samples. The calibration curves were linear from 0.05 to 200 ng mL −1 for fenchlorphos, pirimiphos-methyl, chlorpyrifos, ethion and from 0.2 to 200 ng mL −1 for quinalphos, and the limits of detection were between 5.2 and 34.6 ng L −1. The recovery of the OPPs spiked in real water samples at 5 ng mL −1 ranged from 86.2 to 103.4% and the relative standard deviations were less than 8.5%.

In-capillary derivatization and laser-induced fluorescence detection for the analysis of organophosphorus pesticides by micellar electrokinetic chromatography

We developed a rapid and sensitive method using in-capillary derivatization and laser-induced fluorescence (LIF) detection for the fully automated analysis of organophosphorus pesticides (OPPs), including glufosinate, aminomethylphosphonic acid (AMPA) and glyphosate by micellar electrokinetic chromatography (MEKC). The potential of 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as in-capillary derivatization reagent is described for the first time. The unique feature of this MEKC method is the capillary being used as a small reaction chamber. In in-capillary derivatization, the sample and reagent solutions were injected directly into the capillary by tandem mode, followed by an electrokinetic step to enhance the mixing efficiency of analytes and reagent plugs in accordance with their different electrophoretic mobilities. Standing a specified time for reaction, the derivatives were then immediately separated and determined. Careful optimization of the derivatization and separation conditions allowed the determination of glufosinate, AMPA and glyphosate with detection limits of 2.8, 3.6 and 32.2 ng/mL, respectively. These detection limits were comparable to those of 1.4, 1.9 and 23.8 ng/mL obtained from conventional pre-capillary derivatization. Furthermore, repeatability better than 0.40% for migration time and 3.4% for peak area, as well as shorter migration time, was obtained. The method was successfully applied to the analysis of spiked river water sample with satisfactory results.

Analysis of Organophosphorus Pesticides in Dried Ground Ginseng Root by Capillary Gas Chromatography−Mass Spectrometry and −Flame Photometric Detection

A method was developed to determine organophosphorus pesticides (OPs) in dried ground ginseng root. Pesticides were extracted from the sample using acetonitrile/water saturated with salts, followed by solid-phase dispersive cleanup, and analyzed by capillary gas chromatography with electron ionization mass spectrometry in selective ion monitoring mode (GC-MS/SIM) and flame photometric detection (GC-FPD) in phosphorus mode. The detection limits for most of the pesticides were 0.025-0.05 microg/g using GC-FPD but were analyte-dependent for GC-MS/SIM, ranging from 0.005 to 0.50 microg/g. Quantitation was determined from 0.050 to 5.0 microg/g with r 2 > 0.99 for a majority of the pesticides using both detectors. Recovery studies were performed by fortifying the dried ground ginseng root samples to concentrations of 0.025, 0.1, and 1.0 microg/g, resulting in recoveries of >90% for most pesticides by GC-FPD. Lower (<70%) and higher (>120%) recoveries were most likely from complications of pesticide lability or volatility, matrix interference, or inefficient desorption from the solid-phase sorbents. There was difficulty in analyzing the ginseng samples for the OPs using GC-MS at the lower fortification levels for some of the OPs due to lack of confirmation. GC-FPD and GC-MS/SIM complement each other in detecting the OPs in dried ground ginseng root samples. This procedure was shown to be effective and was applied to the analysis of OPs in ginseng root samples. One particular sample, a ground and dried American ginseng (Panax quinquefolius) root sample, was found to contain diazinon quantified at approximately 25 microg/kg by external calibration using matrix-matched standards or standard addition using both detectors. The advantage of using both detectors is that confirmation can be achieved using GC-MS, whereas the use of a megabore column in GC-FPD can be used to quantitate some of the nonpolar OPs without the use of matrix-matched standards or standard addition.

In-tube solid-phase microextraction-capillary liquid chromatography as a solution for the screening analysis of organophosphorus pesticides in untreated environmental water samples

This paper describes a method for the selective screening of organophosphorus pesticides in water. In-tube solid-phase microextraction (SPME) in an open capillary column coupled to capillary liquid chromatography (LC) with UV detection has been used to effect preconcentration, separation and detection of the analytes in the same assembly. For in-tube SPME two capillary columns of the same length and different internal diameters and coating thicknesses have been tested and compared, a 30 cm × 0.25 mm I.D., 0.25 μm thickness coating column, and a 30 cm × 0.1 mm I.D., 0.1 μm of coating thickness column. In both columns the coating was 95% dimethylpolysiloxane (PDMS)-5% diphenylpolysiloxane. The proposed methodology provided limits of detections (LODs) for the tested organophosphorus pesticides in the 0.1–10 μg/L range, whereas the direct injection of the samples onto the capillary LC system provided LODs in the 50–1000 μg/L range. The sensitivity of the proposed in-tube SPME-capillary LC method is adequate to monitorize the analyte levels in drinking water. Several triazines, polycyclic aromatic hydrocarbons (PAHs), nonylphenol, organochloride pesticides or polybrominated diphenyl ethers (PBDEs) have been evaluated as possible interferents. The reliability of the described method is demonstrated by analysing different real water samples.

A SoC and LED based reconfigurable subminiature spectrometer for hand-held measurement applications

This paper discusses a novel reconfigurable subminiature spectrometer named RSS, which is based on LED as the light source and integrated photodiode IC as the sensor. This device uniquely uses System-on-a-Chip (SoC) as the core unit of the intelligent spectrometer. The main functions of the intelligent spectrometer, such as multi-channel A/D conversion, data storage, real-time clock, firmware updating, etc., are implemented only on one SoC chip. This one-chip-design reduces the price and complexity of the system, increases the stability of spectrometer, and subminiaturizes the device dimensions. It is quite fit for hand-held measurement applications. Furthermore, the replaceable measurement module design and firmware updating function boost up the expandability of RSS. As the applications of RSS, the absorbance measurement of NH 3-N and kinetic analysis of organophosphorus pesticide are demonstrated. The performance evaluation and algorithm improvement in those applications are also discussed.

Analysis of Organophosphorus Pesticides in Whole Milk by Solid Phase Microextraction Gas Chromatography Method

Solid phase microextraction (SPME) was used for the extraction of residual coumaphos and dichlorvos in whole milk. The residues were analyzed by capillary gas chromatography equipped with nitrogen phosphorus detector (GC-NPD). A manual SPME holder with a 100-μm polyacrylate fiber was used. The optimized conditions for extraction by SPME method were: sample agitation, absorption temperature of 30°C, absorption time of 40 min, desorption time of 10 min, and sample volume was 16.0 mL in the vial. Under these conditions, the calibration graphs were linear in the range of 0.17 μgL−1 to 1.75 μgL−1 for coumaphos and 0.69 μgL−1 to 6.90 μgL−1 for dichlorvos. Precision was good with RSD values of 13% for coumaphos and 14% for dichlorvos. The detection limits (LOD) were 0.060 μgL−1 for dichlorvos and 0.052 for coumaphos. The quantification limits (LOQ) were 0.086 μgL−1 for dichlorvos and 0.066 μgL−1 for coumaphos. The results obtained in this study suggest that SPME is a suitable technique for residual pesticide analysis of milk. The data demonstrate that particular OP pesticides used in dairy farming in the region of Minas Gerais were found to contaminate cow whole milk, and the residues are not removed by treating the milk by boiling.

Application of a single-drop microextraction for the analysis of organophosphorus pesticides in juice

In this study, a new method for the determination of organophosphorus pesticides (OPPs) (ethoprophos, diazinon, parathion methyl, fenitrothion, malathion, isocarbophos and quinaphos) in orange juice was developed. Single-drop microextraction (SDME) parameters, such as organic solvent, drop volume, agitation rate, extraction time, and salt concentration were optimized through analysis of OPPs in fortified water. The orange juice was simply centrifuged and diluted with water, extracted by SDME and analyzed by gas chromatography (GC) equipped with a flame photometric detection (FPD). Fortification tests were conducted for concentrations between 10 and 500 μg/L; mean relative recoveries for each pesticide were all above 76.2% and below 108.0%. Limits of detection of the method for orange juice were below 5 μg/L for all target pesticides. The repeatability of the proposed method, expressed as relative standard deviation varied between 4.6 and 14.1% ( n = 5). The proposed method is acceptable in the analysis of OPPs pesticides in juice matrices.

Use of SPME extraction to determine organophosphorus pesticides adsorption phenomena in water and soil matrices

Solid-phase micro extraction (SPME) coupled with GC enables rapid and simple analysis of organophosphorus pesticides in a range of complex matrices. Investigations were made into the extraction efficiencies from water of six organophosphorus insecticides (methamidophos, omethoate, dimethoate, parathion methyl, malathion, and parathion ethyl) showing a wide range of polarities. Three SPME fibres coated with different stationary phases, polydimethylsiloxane, polyacrylate, and carbowax-divinylbenzene (CW-DVB), were investigated. Water was spiked with the pesticides at concentrations from 1 to 0.01 µg mL-1, and the solutions used for optimization of the procedure. The CW-DVB fibre, with a 65 µm coating, gave the best performance. The optimized experimental conditions were sample volume 10 mL at 20°C, equilibration time 16 min, pH 5, and presence of 10% w/v NaCl. SPME analyses were performed on solutions obtained by equilibrating aqueous pesticide solutions with six certified soils with various physico-chemical characteristics. SPME data were also assessed by comparison with analyses performed by using conventional solid-phase extraction. Results indicate the suitability of SPME for analysis of pesticides in environmental water samples.

Optimization of a single-drop microextraction procedure for the determination of organophosphorus pesticides in water and fruit juice with gas chromatography-flame photometric detection

A single-drop microextraction (SDME) procedure was developed for the analysis of organophosphorus pesticides (OPPs) in water and fruit juice by gas chromatography (GC) with flame photometric detection (GC-FPD). The significant parameters affecting the SDME performance such as selection of microextraction solvent, solvent volume, extraction time, stirring rate, sample pH and temperature, and ionic strength were studied and optimized. Two types of SDME mode, static and cycle-flow SDME, were evaluated. The static SDME procedure provided more sensitive analysis of the target analytes. Therefore, static SDME with tributyl phosphate (TBP) as internal standard was selected for the real sample analysis. The limits of detection (LODs) in water for the six studied compounds were between 0.21 and 0.56 ng/mL with the relative standard deviations ranging from 1.7 to 10.0%. Linear response data was obtained in the concentration range of 0.5–50 ng/mL (except for dichlorvos 1.0–50 ng/mL) with correlation coefficients from 0.9995 to 0.9999. Environmental water sample collected from East Lake and fruit juice samples were successfully analyzed using the proposed method, but none of the analytes in both lake water and fruit juice were detected. The recoveries for the spiked water and juice samples were from 77.7 to 113.6%. Compared with the conventional methods, the proposed method enabled a rapid and simple determination of organophosphorus pesticides in water and fruit juice with minimal solvent consumption and a higher concentration capability.

Determination of ethoprop, diazinon, disulfoton and fenthion using dynamic hollow fiber-protected liquid-phase microextraction coupled with gas chromatography–mass spectrometry

A technique for the analysis of organophosphorus pesticides (ethoprop, diazinon, disulfoton, fenthion) in aqueous sample using liquid-phase microextraction (LPME), coupled with gas chromatography–mass spectrometry (GC–MS) was developed. A small section of a hollow fiber inserted into the needle of GC syringe and filled with the 3.5 μl of organic solvent was used to extract pesticides from a 20 ml aqueous sample. The limits of detection (LOD) with the selected ion monitoring (SIM) mode varied from 0.2 to 0.006 μg/l. The calibration curves were linear over three orders of magnitude with R 2 ≥ 0.996. The relative standard deviations of the analysis (inter- and intra-day) were 5–8%, and the relative recoveries from the lake water sample were greater than 83%. The results were compared with results obtained using solid-phase microextraction (SPME/GC/MS).

An Approach to the Application of Microwave-Assisted Micellar Extraction and Liquid Chromatography with Ultraviolet Detection to the Extraction and Determination of Organophosphorus Pesticides in Tomato Samples

Microwave-assisted micellar extraction methodology was applied to extract a mixture of 8 organophosphorus pesticides from the cuticle of tomato samples prior to analysis by liquid chromatography with ultraviolet detection. This technique provided very good results and was simple, fast, and environmentally friendly. The pesticides under study were extracted using the nonionic surfactants polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monoalkyl ether (Genapol X-080). The optimal extraction variables to be applied were determined for each surfactant and then compared. POLE proved to be the most suitable for the extraction, with recoveries over 70% in the majority and relative standard deviation values under 4.8%. After validation using a tomato sample enriched with a certified mixture, the proposed method was applied to the analysis of organophosphorus pesticides in lettuce and pepper samples.