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In this study, a new microextraction method based on hydrophobic deep eutectic solvents was developed for the extraction and preconcentration of organophosphorus pesticides from beverage samples. The hydrophobic deep eutectic solvents were synthesized from choline chloride and 4-chlorophenol. Main experimental parameters of the microextraction method were investigated to improve the extraction efficiency. The proposed method achieved a satisfactory linear range between 50 and 2,000 μg L−1 with coefficient of determination greater than 0.9939. The extraction recoveries and enrichment factor of five organophosphorus pesticides at three added levels ranged from 71.68 to 113.18% and 71.43–111.11 were obtained with the acceptable relative standard deviation ranged from 1.37 to 11.92%. Limits of detection and quantification were found to be 0.05–0.3 μg L−1 and 0.17–1 μg L−1, respectively. Finally, the methods were successfully applied for the determination of five organophosphorus pesticide in orange juice and green tea.

Imidaclothiz is a novel and systemic neonicotinoid pesticide with excellent insecticidal efficacy. However, knowledge of its uptake, translocation, and biotransformation within plants is still largely unknown, restricting work on its accurate and comprehensive risk assessment. Here, we systematically investigated the behavior of imidaclothiz in three plant-water systems via hydroponic experiments. The results showed that imidaclothiz was readily taken up by plant roots and translocated upward, resulting in relative enrichment in leaves. The recoveries of imidaclothiz in plant-water systems decreased with increasing exposure time, and approximately 31.8-45.6% mass loss was measured at the end of exposure. Ultimately, imidaclothiz yielded five products in celery leaves, three products in lettuce leaves, and two products in radish leaves. Multiple metabolic reactions including hydroxylation, hydrolysis of nitrate ester, and methylation occurred within plants. This is the first report on the fate of imidaclothiz within plants and suggests increasing concerns about the risk assessment of imidaclothiz.

To evaluate the residue behavior and risk of pyraclostrobin and tebuconazole in peppers, an analytical method for the determination of these two fungicides in peppers was developed using Ultra-high Performance Liquid Chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS). Pepper samples were extracted with acetonitrile, and cleaned up with primary secondary amine (PSA) and graphitized carbon black (GCB). The average recoveries for three fortification levels of pyraclostrobin and tebuconazole in peppers were 86.7-101.4% and 81.7-104.4% with relative standard deviations (RSDs) of 4.0-7.2% and 3.8–10.9%, respectively. The limit of quantifications (LOQs) for the two fungicides in peppers were 0.01 mg/kg. Terminal residue trial of 30% pyraclostrobin and tebuconazole suspension concentrate (SC) on peppers was investigated under open fields and greenhouses conditions. The results showed that the terminal residues of pyraclostrobin and tebuconazole in peppers were lower than the maximum residue limits (MRLs) of peppers established by GB 2763 − 2021 (0.5 mg/kg for pyraclostrobin and 2 mg/kg for tebuconazole). A statistical t-test was used to study the significant difference between open fields and greenhouses, and the results indicated that there is no significant difference between different planting conditions of greenhouses and open fields. Using international estimate of short-term intake (IESTI) calculation model of Joint FAO/WHO Meeting on Pesticide Residues (JMPR), the acute dietary exposure risk of two fungicides in peppers was acceptable for general population with the IESTIs varied from 0–3% of ARfD for pyraclostrobin and 0–5% for tebuconazole.

The fungal species Fusarium can cause devastating disease in agricultural crops. Phenamacril is an extremely specific cyanoacrylate fungicide and a strobilurine analog that has excellent efficacy against Fusarium. To date, information on the mechanisms involved in the uptake, accumulation, and metabolism of phenamacril in plants is scarce. In this study, lettuce and radish were chosen as model plants for a comparative analysis of the absorption, accumulation, and metabolic characteristics of phenamacril from a polluted environment. We determined the total amount of phenamacril in the plant-water system by measuring the concentrations in the solution and plant tissues at frequent intervals over the exposure period. Phenamacril was readily taken up by the plant roots with average root concentration factor ranges of 60.8-172.7 and 16.4-26.9 mL/g for lettuce and radish, respectively. However, it showed limited root-to-shoot translocation. The lettuce roots had a 2.8-12.4-fold higher phenamacril content than the shoots; whereas the radish plants demonstrated the opposite, with the shoots having 1.5 to 10.0 times more phenamacril than the roots. By the end of the exposure period, the mass losses from the plant-water systems reached 72.0% and 66.3% for phenamacril in lettuce and radish, respectively, suggesting evidence of phenamacril biotransformation. Further analysis confirmed that phenamacril was metabolized via hydroxylation, hydrolysis of esters, demethylation, and desaturation reactions, and formed multiple transformation products. This study furthers our understanding of the fate of phenamacril when it passes from the environment to plants and provides an important reference for its scientific use and risk assessment.

In this study, a simple and accurate sample preparation method based on dispersive solid-phase extraction and dispersive liquid-liquid microextraction has been developed for the determination of seven novel succinate dehydrogenase inhibitor fungicides (isopyrazam, fluopyram, pydiflumetofen, boscalid, penthiopyrad, fluxapyroxad, and thifluzamide) in watermelon. The watermelon samples were extracted with acetonitrile, cleaned up by dispersive solid-phase extraction procedure using primary secondary amine, extracted and concentrated by the dispersive liquid-liquid microextraction procedure with 1,1,2,2-tetrachloroethane, and then analyzed by ultra high performance liquid chromatography with tandem mass spectrometry. The main experimental factors affecting the performance of dispersive solid-phase extraction and dispersive liquid-liquid microextraction procedure on extraction efficiency were investigated. The proposed method had a good linearity in the range of 0.1-100 µg/kg with correlation coefficients (r) of 0.9979-0.9999. The limit of quantification of seven fungicides was 0.1 µg/kg in the method. The fortified recoveries of seven succinate dehydrogenase inhibitor fungicides at three levels ranged from 72.0 to 111.6% with relative standard deviations of 3.4-14.1% (n = 5). The proposed method was successfully used for the rapid determination of seven succinate dehydrogenase inhibitor fungicides in watermelon.

The dissipation and residue levels of thiamethoxam and its metabolite clothianidin in cowpea were investigated under field conditions. Samples of cowpea were analyzed using a QuEChERS technique with ultra-performance liquid chromatography tandem mass spectrometry. The recoveries were 86.5-118.9% for thiamethoxam and 75.6-104.1% for clothianidin, with the coefficient of variation of < 13%. The water dispersible granule formulation of thiamethoxam was applied on cowpea at 30 and 45 g active ingredient ha-1 in accordance with good agricultural practice. The half-life of thiamethoxam in cowpea was 0.8-1.6 days. The cowpea samples were gathered at 3, 7, and 10 days after the last application, and the residues of thiamethoxam in cowpea were < 0.005-0.054 mg kg-1, while those of clothianidin were < 0.005-0.008 mg kg-1. The final residues of thiamethoxam and clothianidin were below the European Union (EU) maximum residue level (0.3 mg kg-1 for thiamethoxam; 0.2 mg kg-1 for clothianidin) in cowpea after a preharvest interval (PHI) of 7 days. This study provided basic data on the use and safety of thiamethoxam and clothianidin in cowpea to help the Chinese government formulate a maximum residue level for thiamethoxam in cowpea.

The residue behavior and dietary intake risks of carbosulfan and its metabolites in cucumbers were investigated. A quick and reliable method for determining carbosulfan and its metabolite residues in cucumbers was established using ultrahigh performance liquid chromatography–tandem mass spectrometry. The fortified recoveries ranged from 87.2% to 91.0% with relative standard deviations of 3.2%–8.1%. The dissipation results showed that carbosulfan was transformed into carbofuran and 3-hydroxy carbofuran in cucumbers. The half-life of carbosulfan was 1.5 days, and the half-life of carbofuran was 45 days. The final residues of carbosulfan varied from 0.245 to 0.005 mg/kg and carbofuran varied from 0.123 to 0.008 mg/kg. After a 5-day application period the residues of carbosulfan was 0.113 mg/kg that was below the maximum residue limit set by China (0.2 mg/kg), and the residues of carbofuran was 0.055 mg/kg that was higher than the maximum residue limit set by China (0.02 mg/kg). The risk assessment results indicated that the dietary intake risks of carbosulfan and carbofuran from cucumber consumption were safe for Chinese consumers, but pre-harvest intervals should be strictly recommended for 7 days at the recommended dose to ensure that food quality conforms to the MRL standard. This study provides a method and data for scientifically evaluating dietary intake risks of carbosulfan and its more toxic metabolites.

A rapid, selective and sensitive sample preparation method based on solid-phase extraction combined with the dispersive liquid-liquid microextration was developed for the determination of pyrethroid pesticides in wheat and maize samples. Initially, the samples were extracted with acetonitrile and water solution followed phase separation with the salt addition. The following sample preparation involves a solid-phase extraction and dispersive liquid-liquid microextraction step, which effectively provide cleanup and enrichment effects. The main experimental factors affecting the performance both of solid-phase extraction and dispersive liquid-liquid microextration were investigated. The validation results indicated the suitability of the proposed method for routine analyze of pyrethroid pesticides in wheat and maize samples. The fortified recoveries at three levels ranged between 76.4 and 109.8% with relative standard deviations of less than 10.7%. The limit of quantification of the proposed method was below 0.0125 mg/kg for the pyrethoroid pesticides. The proposed method was successfully used for the rapid determination of pyrethroid residues in real wheat and maize samples from crop field in Beijing, China.

The residue behavior and dietary intake risk of three fungicides (pyrimethanil, iprodione, kresoxim-methyl) in tomatoes ( Lycopersicon esculentum Mill.) grown in greenhouse were investigated. A simple, rapid analytical method for the quantification of fungicide residues in tomatoes was developed using gas chromatography coupled with mass spectrum detection (GC-MSD). The fortified recoveries were ranged from 87% to 103% with relative standard deviations (RSDs) varied from 4.7% to 12.1%. The results indicated that the dissipation rate of the studied fungicides in tomatoes followed first order kinetics with half lives in the range of 8.6–11.5 days. The final residues of all the fungicides in tomatoes were varied from 0.241 to 0.944 mg/kg. The results of dietary intake assessment indicated that the dietary intake of the three fungicides from tomatoes consumption for Chinese consumers were acceptable. This study would provide more understanding of residue behavior and dietary intake risk by these fungicides used under greenhouse conditions.

This study demonstrates a new, rapid, and sensitive analytical method for the simultaneous determination of tebufenozide and phoxim in cabbage and soil using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation procedure followed by ultrahigh-performance liquid chromatography coupled with tandem mass spectrometry. Tebufenozide and phoxim were extracted with acetonitrile and subsequently cleaned up with a primary and secondary amine sorbent prior to sample analysis. Recoveries ranged from 77.2 to 107.3 % for all analytes, with relative standard deviation values lower than 8.8 % in matrices at three levels (0.005, 0.01, 0.1 mg/kg). The limit of quantification for tebufenozide and phoxim in cabbages and soil was 0.005 mg/kg, respectively. The developed method was used to study the dissipation of the pesticides in cabbage and soil in a field trial. The tebufenozide and phoxim dissipated with half-life of 4.5–4.8 and 0.7–0.7 days (in cabbage) and 10.8–12.7 and 1.1–1.5 days (in soil), respectively. The final residue concentrations of tebufenozide and phoxim were 0.022–0.482 and 0.029–0.042 mg/kg (in cabbage) and 0.029–0.487 and 0.025–0.043 mg/kg (in soil), respectively. The results further confirmed the reliability and efficacy of the proposed method for routine pesticide residue monitoring in soil and cabbage samples.

A new combined difenoconazole and fluxapyroxad fungicide formulation, as an 11.7 % suspension concentrate (SC), has been introduced as part of a resistance management strategy. The dissipation of difenoconazole and fluxapyroxad applied to apples and the residues remaining in the apples were determined. The 11.7 % SC was sprayed onto apple trees and soil in Beijing, Shandong, and Anhui provinces, China, at an application rate of 118 g a.i. ha(-1), then the dissipation of difenoconazole and fluxapyroxad was monitored. The residual difenoconazole and fluxapyroxad concentrations were determined by ultrahigh-performance liquid chromatography tandem mass spectrometry. The difenoconazole half-lives in apples and soil were 6.2-9.5 and 21.0-27.7 days, respectively. The fluxapyroxad half-lives in apples and soil were 9.4-12.6 and 10.3-36.5 days, respectively. Difenoconazole and fluxapyroxad residues in apples and soil after the 11.7 % SC had been sprayed twice and three times, with 10 days between applications, at 78 and 118 g a.i. ha(-1) were measured. Representative apple and soil samples were collected after the last treatment, at preharvest intervals of 14, 21, and 28 days. The difenoconazole residue concentrations in apples and soil were 0.002-0.052 and 0.002-0.298 mg kg(-1), respectively. The fluxapyroxad residue concentrations in apples and soil were 0.002-0.093 and 0.008-1.219 mg kg(-1), respectively. The difenoconazole and fluxapyroxad residue concentrations in apples were lower than the maximum residue limits (0.5 and 0.8 mg kg(-1), respectively). An application rate of 78 g a.i. ha(-1) is therefore recommended to ensure that treated apples can be considered safe for humans to consume.

Fluazinam and dimethomorph 35% suspension concentrate (SC) is a new combined fungicide formulation introduced in China to improve fungicidal efficacy and decrease the risk of resistance in potatoes. Fluazinam and dimethomorph dissipation and residues in potatoes, potato plants, and soil under field conditions were determined by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Fluazinam and dimethomorph 35% SC was applied at two doses to potatoes and soil in Ningxia Autonomous Region and Anhui Province, China. Fluazinam and dimethomorph dissipation fitted first-order kinetics, and the fluazinam half-lives in potato plants and soil were 3.3–5.4 and 9.4–9.5 days, respectively. The dimethomorph half-lives in potato plants and soil were 2.1–2.6 and 5.9–8.6 days, respectively. Fluazinam and dimethomorph 35% SC was sprayed onto potato plants three or four times at application rates of 420 and 630 g a.i. ha−1 with 7 days between applications. Potato and soil samples were collected at 3, 7, and 14 days after the last application. Potatoes and soil had fluazinam concentrations of

In order to study the dissipation rates and final residues of kresoxim-methyl in strawberry and soil, two independent filed trials were performed in Beijing China. The application rates are set at 195 g of active gradient per hectare. A simple analytical method has been developed for the determination of kresoxim-methyl in strawberry and soil. Kresoxim-methyl residues were extracted with acetonitrile from strawberry and soil samples which is determined by gas chromatography coupled with mass spectrometry detection (GC-MSD). The recoveries of kresoxim-methyl in strawberry and soil were observed from 78.9 % to 104.5 % at fortification levels of 0.01-0.5 mg/kg with relative standard deviations of 4.3 %-7.3 %. The reported limits of detection were 0.05 and 0.01 mg/kg for strawberry and soil, respectively. The results showed that kresoxim-methyl dissipation in strawberry could be described as first-order equation with the half-life time of 6.24 and 6.91 days. 14 days later, the dissipation rate is 84.9 % and 83.3 %, respectively. The final residues of kresoxim-methly in the strawberry were in the range of 2.7-4.8 mg/kg at pre-harvest intervals of 1, 3, 5, 7 days which is below the Japan maximum residue limits (MRLs) standards (5 mg/kg in strawberry).

BACKGROUND The residue concentrations and dissipation rate of a new oxathiapiprolin fungicide in grapes and soil were investigated to provide an evaluation for the safe use of oxathiapiprolin in grapes. Pesticide residue was extracted by acetonitrile, then purified by solid-phase extraction with an Envi-Carb cartridge and determined by ultrahigh-performance liquid chromatography–tandem mass spectrometry. RESULTS The fortified recoveries ranged from 85.2% to 99.0%, with relative standard deviations of 1.7–4.5%. The limit of quantitation for oxathiapiprolin in grapes and soil was 0.002 mg kg−1. The mean initial deposits of oxathiapiprolin in grapes were 0.345–0.565 mg kg−1, with half-lives of 8.6–9.2 days. The mean initial deposits of oxathiapiprolin in soil were 0.078–0.273 mg kg−1, with half-lives of 7.6–12.0 days. The oxathiapiprolin residue in grapes and soil was 0.002–0.022 mg kg−1 and 0.002–0.123 mg kg−1 when sampling 14 days after application, respectively. CONCLUSION The residue in the grapes was less than 0.01 mg kg−1 when sampling 28 days after application, which suggested that the application rate of 20 mg a.i. kg−1 for this fungicide should be used to ensure that treated grapes can be considered safe for humans to consume when sampling 28 days after the final application. © 2016 Society of Chemical Industry

A rapid, selective and sensitive sample preparation method based on solid-phase extraction combined with the dispersive liquid-liquid microextration was developed for the determination of pyrethroid pesticides in wheat and maize samples. Initially, the samples were extracted with acetonitrile and water solution followed phase separation with the salt addition. The following sample preparation involves a solid-phase extraction and dispersive liquid-liquid microextraction step, which effectively provide cleanup and enrichment effects. The main experimental factors affecting the performance both of solid-phase extraction and dispersive liquid-liquid microextration were investigated. The validation results indicated the suitability of the proposed method for routine analyze of pyrethroid pesticides in wheat and maize samples. The fortified recoveries at three levels ranged between 76.4 and 109.8% with relative standard deviations of less than 10.7%. The limit of quantification of the proposed method was below 0.0125 mg/kg for the pyrethoroid pesticides. The proposed method was successfully used for the rapid determination of pyrethroid residues in real wheat and maize samples from crop field in Beijing, China.

In this article, a simple and efficient method using gas chromatography–mass spectrometry (GC-MS) was developed to determine carbofuran and 3-hydroxy carbofuran in maize and soil. Field experiments...

In this study, a solid-phase microextraction (SPME) method based on a bare stainless steel wire as the fiber has been developed for extraction and determination of five pyrethroid insecticides (fenpropathrin, cyhalothrin, cypermethrin, fenvalerate and deltamethrin) in water and soil samples. The influences of extraction parameters (extraction time, stirring rate and salt addition) on the SPME extraction efficiency were investigated, and the optimum conditions were applied for the extraction of the target analytes from water samples. The method showed linear behavior ranging from 0.05 to 2 µg L−1 with detection limits of 0.6–1.9 ng L−1 for water analysis. Recoveries were from 71 to 112% for all the target insecticides in water and soil sample, with RSDs from 6.8 to 19.4% (n = 3). The study demonstrated the feasibility of the proposed SPME fiber based on stainless steel wire for the extraction of pyrethroid insecticides in water and soil.

A simple solvent microextraction method termed vortex-assisted liquid-liquid microextraction (VALLME) coupled with gas chromatography micro electron-capture detector (GC-microECD) has been developed and used for the pesticide residue analysis in water samples. In the VALLME method, aliquots of 30 microL toluene used as extraction solvent were directly injected into a 25 mL volumetric flask containing the water sample. The extraction solvent was dispersed into the water phase under vigorously shaking with the vortex. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition were investigated. Under the optimum condition, enrichment factors (EFs) in a range of 835-1115 and limits of detection below 0.010 microg L(-1) were obtained for the determination of target pesticides in water. The calculated calibration curves provide high levels of linearity yielding correlation coefficients (r(2)) greater than 0.9958 with the concentration level ranged from 0.05 to 2.5 microg L(-1). Finally, the proposed method has been successfully applied to the determination of pesticides from real water samples and acceptable recoveries over the range of 72-106.3% were obtained.

SYP-1924 is a new kind of herbicide developed by Shenyang Scicncreat Chemicals. This study has been carried out to investigate the environmental fate of SYP-1924 in rice-field system. An analytical method utilizing high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was described for the determination of new kind of herbicide SYP-1924 in rice, rice straw, soil and water. The dissipation of SYP-1924 in soil, water and rice straw was determined using the proposed method. The results showed that dissipation of SYP-1924 in rice straw and water were found to be very faster with half-life time shorter than 1.5 days. The half-life value of SYP-1924 was observed to be 4.5 days in soil. The ultimate residues of SYP-1924 in rice were found to be below the limits of the detection at level of recommended and 1.5 times recommended dosage with an interval date of 70 days.

In this study, a microextraction method termed as ultrasound-assisted emulsification-microextraction (USAEME) has been developed for the extraction of organophosphorus pesticides (OPPs) in water and orange juice samples. In the USAEME method, aliquots of 50 microL chlorobenzene used as extraction solvent was added to 10 mL water sample in a conical glass centrifugal tube. Factors influencing the USAEME extraction efficiency such as sonication time, extraction solvent, extraction volume and salt addition were evaluated. Under the optimum conditions, enrichment factors ranged from 241 to 311, LOD varied from 5.3 to 10.0 ng/L and linearity with a coefficient of estimation (r(2)) varied from 0.9991 to 0.9998 in the concentration level range of 0.05-2.5 microg/L for the extraction of OPPs in water samples. Finally, the proposed USAEME method was used for the extraction of OPPs from water and orange juice. The recoveries were in the range of 80.0-110.0%, and the repeatability of the method expressed as RSD (n=3) varied between 1.6 and 13%. The USAEME method has the advantage of being easy to operate, low consumption of organic solvent and high extraction efficiency.

Multiwalled carbon nanotubes were used as solid phase extraction (SPE) adsorbent for the determination of four chloroacetanilide herbicides (alachlor, acetochlor, metolachlor and butachlor) in water. The primary factors that influence the efficiency of the SPE performance, such as the amount of the adsorbent, the eluent solvent, the pH and the sample volume, were investigated and optimized. Under optimized conditions, the recoveries of the four herbicides at three spike levels were in the range 76.7–104.4%, and the RSDs ranged from 2.5–12.7%. Good linearity was obtained for the pesticides in the concentration range 0.0025–2.5 mg L−1, and the detection limits were 0.01–0.03 μg L−1 at signal-to-noise ratios of 3:1. The method was successfully applied to the determination of these analytes in tap water and river water.

A gas chromatography-mass spectrometry (GC-MS) method for the determination of hexachlorocyclohexane (BHC) and dichlorodiphenyltrichloroethane (DDT) residues in honey was developed using dispersive liquid-liquid microextraction (DLLME) as sample preparation method. The samples were extracted with chloroform, and concentrated into chloroform by vortex and centrifuging. The analytes were analyzed by GC-MS. The factors affecting the extraction efficiency were investigated, such as the type and volume of extraction and dispersive solvent, extraction time, etc. The matrix effects and method performance were evaluated at the same time. The results indicated that all the eight BHC and DDT pesticides displayed the enhancement of signals due to the matrix effects. The calibration curves were linear in the range of 2-500 microg/L and the correlation coefficients were 0.991-0.998 for the eight BHC and DDT pesticides. The enrichment factors (EF) were 74-96 for the eight pesticides. The recoveries of the eight BHC and DDT pesticides at three spiked levels of 20, 50 and 100 microg/kg were 61.0%-100.1%, while the RSDs were 2.2%-19.5%. The limits of quantification for the eight pesticides were 20 microg/kg, and the limits of detection were 1.0 ng. The developed method is easy, quick and with high performance. It is applicable for the determination of BHC and DDT residues in honey.

Single‐drop microextraction (SDME) and gas chromatography microelectron capture detection (GC‐μECD) methods for the determination of four fungicides (chlorothalonil, triadimefon, hexaconazole, and diniconazole) in water and wine were developed. The main parameters affecting the performance of SDME, such as selection of solvent, extraction time, organic drop volume, stirring rate, and salt concentration, were optimized. The relationship of the measured signal was a linear function (>0.993) of concentration. Using chosen procedure in the concentration range of 0.01 to 50 µg l−1(chlorothalonil 0.01 to 25 µg l−1) the detection limits of the determination of studied pesticides in water were in the range of 0.006–0.01 µg l−1(S/N=3), the relative standard deviations (RSDs) 56. The SDME‐GC‐μECD method was performed in natural water, wine, and the recoveries were acceptable.

A chiral stationary phase (CSP) was prepared by bonding emamectin onto unmodified spherical gel. Normal‐phase high performance liquid chromatography (HPLC) methods for the resolution of three chiral triazole pesticides, triadimefon, difenoconazole, and propiconazol, on the CSP were developed. Several operating parameters, such as mobile phase composition, column temperature, and flow rate were studied for the optimization of the resolution. Better separations were achieved using 5% isopropanol for triadimefon, 20% iso‐propanol for difenoconazole, and 5% isopropanol for propiconazol as modifiers, in n‐hexane at 10°C with the selectivity factors (α) of 1.29, 1.29, and 1.48, respectively.

In this article, a new method using single-drop microextraction (SDME) and gas chromatography micro-electron capture detection (GC-μECD) for the determination of chloroacetanilide herbicides (alachlor, acetochlor, metolachlor, pretilachlor and butachlor) residues was developed. The effects of SDME parameters such as extraction solvent, stirring rate, ionic strength, microdrop volume and extraction time were optimized. The optimum experimental conditions found were: 1.6 μl toluene microdrop, 5 ml water sample, 400 rpm stirring rate, 15 min extraction time and no salt addition. Analytical parameters such as linearity, repeatability and limit of detection were also evaluated. The proposed method was proved to be a simple and rapid analytical procedure for chloroacetanilide herbicides in water with limits of detection 0.0002–0.114 μg/l. The relative recoveries range from 80% to 102% for all the target analytes, with the relative standard deviations varying from 3.9% to 11.7%.

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 microg/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 microg/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.

A new analytical method for the determination of organophosphorus pesticides in cereal samples was developed by combining dispersive SPE (d-SPE) and salting-out homogeneous liquid-liquid extraction (SHLLE). The pesticides were first extracted from cereal grains with acetonitrile, followed by d-SPE cleanup. A 2 mL aliquot of the extract was then added to a centrifuge tube containing 9.2 mL water and 3.3 g NaCl for SHLLE. Analysis of the extract was carried out by gas chromatography coupled with flame photometric detection. The d-SPE procedure effectively provides the necessary cleanup of the extract while SHLLE is used as an efficient concentration technique. Experimental parameters influencing the extraction efficiency including amounts of added water and salt were investigated. Recovery studies were carried out at three fortification levels, yielding recoveries in the range of 57.7-98.1% with the RSD from 3.7 to 10.9%. The reported limits of determination obtained from this study were 1 μg/kg, which is better than the conventional methods. In the analysis of 40 wheat and corn samples taken from Beijing suburbs, only two wheat samples have chlorpyrifos residue over the limits of determination.

In this study, a microextraction method termed as ultrasound-assisted emulsification-microextraction (USAEME) has been developed for the extraction of organophosphorus pesticides (OPPs) in water and orange juice samples. In the USAEME method, aliquots of 50 microL chlorobenzene used as extraction solvent was added to 10 mL water sample in a conical glass centrifugal tube. Factors influencing the USAEME extraction efficiency such as sonication time, extraction solvent, extraction volume and salt addition were evaluated. Under the optimum conditions, enrichment factors ranged from 241 to 311, LOD varied from 5.3 to 10.0 ng/L and linearity with a coefficient of estimation (r(2)) varied from 0.9991 to 0.9998 in the concentration level range of 0.05-2.5 microg/L for the extraction of OPPs in water samples. Finally, the proposed USAEME method was used for the extraction of OPPs from water and orange juice. The recoveries were in the range of 80.0-110.0%, and the repeatability of the method expressed as RSD (n=3) varied between 1.6 and 13%. The USAEME method has the advantage of being easy to operate, low consumption of organic solvent and high extraction efficiency.

A specific, sensitive method was developed for the analysis of chlormequat in wheat and soil by high performance chromatography/mass spectrometry. The fortified recoveries of soil were from 75.08% to 96.55%, with RSD 3.34%–15.18%, the limit of detection of the analytical method was 0.05 ng at a signal-to-noise ratio of 3, and the limit of quantification was 0.05, 0.1, 0.5 mg/kg for soil, wheat plants and wheat grain, respectively. The degradation dynamics and final residues of chlormequat in Beijing and Changchun were investigated. The half-life of chlormequat in wheat plants were 3.15 days in Beijing and 4.56 days in Changchun, while the half-life in soil was 3.88 days in Beijing and 4.51 days in Changchun. The final residues of chlormequat in soil were not detectable, and the final residues of chlormequat in wheat grain were below 0.50 mg/kg except for 3.51 mg/kg from high dosage plot of Changchun. The fact that all the final residues were below 5 mg/kg (GB2763 in National standards of the People’s Republic of China, maximum residue limits for pesticide in food, Beijing, 2005) suggested that chlormequat could be safely used in wheat crops with the suitable dosage and application.

A novel microextraction method termed ionic liquid dispersive liquid–liquid microextraction (IL-DLLME) combining high-performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of insecticides in water samples. Four heterocyclic insecticides (fipronil, chlorfenapyr, buprofezin, and hexythiazox) were selected as the model compounds for validating this new method. This technique combines extraction and concentration of the analytes into one step, and the ionic liquid was used instead of a volatile organic solvent as the extraction solvent. Several important parameters influencing the IL-DLLME extraction efficiency such as the volume of extraction solvent, the type and volume of disperser solvent, extraction time, centrifugation time, salt effect as well as acid addition were investigated. Under the optimized conditions, good enrichment factors (209–276) and accepted recoveries (79–110%) were obtained for the extraction of the target analytes in water samples. The calibration curves were linear with correlation coefficient ranged from 0.9947 to 0.9973 in the concentration level of 2–100 μg/L, and the relative standard deviations (RSDs, n = 5) were 4.5–10.7%. The limits of detection for the four insecticides were 0.53–1.28 μg/L at a signal-to-noise ratio (S/N) of 3.

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 microg/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 microg/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.

The purpose of this article was to establish a simple residue analysis method for S-metolachlor in maize and to study its dissipation and residue in maize field eco-system. The results showed that S-metolachlor declined rapidly in maize seedling and soil after application. The half-lives of S-metolachlor in maize seedlings in Beijing and Changchun were 6.68 and 4.85 days, respectively, and in soil were 12.81 and 14.81 days, respectively. The terminal residues of S-metolachlor in soil samples were very low (around 0.005–0.045 mg/kg), and the residues in maize seeds were not detectable. The use of S-metolachlor according to the recommended dosages in maize could be considered safe.

Molecularly imprinted microspheres (MIPMs) for binding and recognition of nicosulfuron (NS) (NS-MIPMs) were prepared by precipitation polymerization. Methacrylic acid (MAA) was used as the functional monomer, trimethylolpropane trimethacrylate (TRIM) as the linking agent, 2,2-azobisisobutyronitrile (AIBN) as the initiator and chloroform as the porogenic solvent. The preparation conditions were optimized, and MIPMs exhibited the best adsorption capacity when the molar ratio of NS/MAA/TRIM/AIBN was 1:4:4:1 and the volume of the porogenic solvent was 90 mL. An ultraviolet-visible (UV-Vis) spectrophotometer was employed to study the mechanism of the interaction between NS and MAA, and the results showed that the NS-MAA complexes of 1:1 molar ratio were obtained in the pre-polymerization phase. The rebinding capacity of MIPMs was evaluated according to adsorption kinetics and adsorption isotherm of the imprinted microspheres. The Scatchard plot revealed that the template polymer system has a two-site binding behavior and the MIPMs exhibited the maximum rebinding to NS at 11,370.5 microg/g. The MIPMs were then used as adsorbents in a solid phase extraction (SPE) column and the optimum loading, washing and eluting conditions for the MIPMs were established. Additionally, a rapid method for the determination of NS residues in soil was developed using an NS-MIPMs SPE column. The analyte was extracted using acetonitrile and phosphate buffer, cleaned-up by an NS-MIPMs SPE column and analyzed by HPLC. The results showed that good linearity was observed in the range of 0.01-1 mg/L for NS, with a correlation coefficient of 0. 998 6. The recovery tests were performed at the spiked levels of 0.02-1 mg/kg, and the recoveries were in the range of 82.2%-86.3% with the relative standard deviations of 1.9%-4.3%. The advantages of the proposed method are that it is easy to operate, reliable and applicable to analyze the NS residues in soil samples.