Dissipation and residue of triforine in strawberry and soil

Two independent field trials were performed in Guangdong and Hubei, China in 2011 to investigate the dissipation and residue levels of triforine in strawberry and soil. A fast and simple method using gas chromatography with electron capture detector was developed and validated to determine triforine levels in strawberry and soil. The average recovery of triforine in strawberry ranged from 87.46 to 104.32 % with a relative standard deviation (RSD) of 0.72 to 4.54 %; that in soil ranged from 83.82 to 103.01 % with an RSD of 3.89 to 4.36 %. The limit of quantification of the proposed method was 0.01 mg/kg for both strawberry and soil. The results suggest that the triforine dissipation curves followed the first-order kinetic. The half-lives of triforine in strawberry from Guangdong and Hubei were 3.58 and 4.42 days, respectively; those in soil were 3.53 and 4.10 days, respectively. The terminal residues of triforine in strawberry ranged from 0.032 to 0.264 mg/kg at preharvest intervals of 0.5, 1, and 3 days. These values are lower than the maximum residue limit of 1 mg/kg in strawberry set by the Codex Alimentarius Commission.     

Dissipation and residue of metalaxyl and cymoxanil in pepper and soil

A simple and accurate method of determining metalaxyl and cymoxanil in pepper and soil was developed by ultra-performance liquid chromatography–photodiode array detection. The limits of detection were 0.015 mg/kg for metalaxyl and 0.003 mg/kg for cymoxanil. The limits of quantification were 0.05 mg/kg for metalaxyl in pepper and soil as well as 0.01 mg/kg for cymoxanil in pepper and soil. Recoveries of pepper and soil were investigated at three spiking levels and ranged within 77.52 to 102.05 % for metalaxyl and 87.15 to 103.21 % for cymoxanil, with relative standard deviations below 9.30 %. For field experiments, the half-lives of metalaxyl were 3.2 to 3.9 days in pepper and 4.4 to 9.5 days in soil at the three experimental locations in China. At harvest, pepper samples were found to contain metalaxyl and cymoxanil well below the maximum residue limit MRLs of the European Union (EU) following the recommended dosage and the interval of 21 days after last application.     

Dissipation and residue of 2,4-D isooctyl ester in wheat and soil

A simple analytical method was developed to determine the 2,4-D isooctyl ester residue in wheat and soil by gas chromatography coupled with electron capture detector. Using the method, the dissipation and residue of 2,4-D isooctyl ester in wheat field was investigated. The average recoveries of 2,4-D isooctyl ester ranged from 80.1% to 110.0% with relative standard deviations of 2.4% to 16.1%. The pesticide showed a rapid dissipation rate either in wheat seedling or soil, with the half-lives of 1.0 to 3.0 days. The terminal residue results in wheat grain were much lower than the codex MRL (2.0 mg/kg). It could be considered safe to food and environment when using this herbicide for controlling weeds in wheat field.     

Dissipation and residue of MCPA (4-chloro-2-ethylphenoxyacetate) in wheat and soil

A rapid and simple HPLC method has been developed for the quantitation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in both wheat and soil samples. Samples were extracted in acidic media and cleaned up by solid-phase extraction with C(18) cartridges before HPLC-DAD detection. The limits of detection and quantification of MCPA were 0.02 ng and 0.01 mg/kg for both wheat and soil. The mean recoveries ranged from 87.1% to 98.2%, and the RSDs ranged from 0.604% to 3.44% for the three spiked levels (0.01, 0.1, 0.5 mg/kg). The proposed method was successfully applied to the analysis of MCPA residues in wheat and soil samples from an experimental field. The dissipation half-lives in soil were calculated to be 3.22 days (Beijing) and 3.10 days (Tianjin), respectively. Direct confirmation of the analytes in real samples was achieved by gas chromatography-mass spectrometry. The results indicated that at harvest time, the residues of MCPA in wheat were well below the maximum residue levels and were safe to apply in wheat.     

Dissipation dynamic and residue distribution of flusilazole in mandarin

In this paper, dissipation dynamic and terminal residue of flusilazole in mandarin and soil, as well as residue distribution of flusilazole in mandarin, were studied at three sites in China. Mandarin peel, mandarin pulp, whole mandarin, and soil samples were extracted by acetonitrile, cleaned up with dispersive solid-phase extraction, then analyzed by gas chromatography–mass spectrometry. The dissipation half-lives of flusilazole in mandarin and soil at all three experiment sites were 6.3–8.4 days and 5.5–13.4 days, respectively, with the exception of the soil dissipation at the Hunan site, which showed an increase–decrease process. Flusilazole residue levels in whole mandarin were all below 0.1 mg/kg on 14 days after the last application. Terminal residue study showed that flusilazole was mostly distributed in mandarin peel, which indicates minimal risk for eating mandarin pulp. These results could provide guidance for the proper and safe use of flusilazole on citrus fruits, and further our understanding of pesticide distribution in citrus fruits.     

Dissipation and residue of azoxystrobin in banana under field condition

A method was developed for determining azoxystrobin in banana and cultivation soil using gas chromatography. The dissipation and residue of azoxystrobin in banana fields at GAP conditions were investigated. The average recoveries ranged from 80.3 to 96.0 % with relative standard deviations of 2.9 to 7.2 % at three different spiking levels for each matrix. The results indicated that the half-life of azoxystrobin in bananas and soil ranged from 7.5 to 13.5 days in Guangdong and from 8.7 to 12.7 days in Fujian. The dissipation rates of azoxystrobin in banana and soil were almost the same. Terminal residues in banana and banana flesh (0.01 mg/kg) were all below the maximum residue limit (2 mg/kg by Codex Alimentarius Commission and China). The results demonstrated that the safety of using azoxystrobin at the recommended agriculture dosage to protect bananas from diseases.     

Dissipation pattern and pre-harvest residue limit of abamectin in perilla leaves

The pre-harvest residue limit (PHRL) of abamectin (abamectin B1a and B1b) in Perilla frutescens leaves grown under greenhouse conditions were investigated using high-performance liquid chromatography with a fluorescence detector. Samples were extracted with acetonitrile. The extract was purified through a solid phase extraction procedure. Then the purified extract was derivatized with trifluoroacetic anhydride and N-methylimidazole to form a strong stable fluorescent derivative of abamectin. Finally, derivatized abamectins were conveyed to the detector via an Atlantis C₁₈ column, with water and methanol as a mobile phase. Calibration curves were linear over the calibration ranges with coefficients of determinants r ²?≥?0.999. The limits of detection and quantification were 0.0033 and 0.01 mg kg^?1 for abamectin B_1a and B_1b, respectively. Recovery was assessed in a control matrix at two different fortification concentrations, with three replicates for each concentration. Good recoveries were obtained for the target analytes and ranged from 82.11 to 93.03 %, with relative standard deviations of less than 8 %. The rate of disappearance of total abamectin on perilla leaves for recommended and double the recommended doses was described as first-order kinetics with a half-life of 0.7 days. Using the PHRL curve, we could predict the residue level of total abamectin to be 0.92 mg kg^?1 at 7 days before harvest or 0.26 mg kg^?1 at 4 days before harvest, which would be below the provisional MRL designed by the Korea Food and Drug Administration.     

Dissipation and residue behavior of mepiquat on wheat and potato field application

A modified LC-MS method for the analysis of mepiquat residue in wheat, potato, and soil was developed and validated. A hydrophilic interaction liquid chromatographic column has been successfully used to retain and separate the mepiquat. Mepiquat residue dynamics and final residues in supervised field trials at Good Agricultural Practice (GAP) conditions in wheat, potato, and soil were studied. The limits of quantification for mepiquat in all samples were all 0.007 mg kg^?1, which were lower than their maximum residue limits. At fortification levels of 0.04, 0.2, and 2 mg kg^?1 in all samples, recoveries ranged from 77.5 to 116.4 % with relative standard deviations of 0.4–7.9 % (n?=?5). The dissipation half-lives (T _1/2) of mepiquat in soil (wheat), wheat plants, soil (potato), and potato plants were 4.5–6.3, 3.0–5.6, 2.2–4.6, and 2.4–3.2 days, respectively. The final residues of mepiquat were below 0.153 mg kg^?1 in soil (wheat), 0.052–1.900 mg kg^?1 in wheat, below 0.072 mg kg^?1 in soil (potato), and below 1.173 mg kg^?1 in potato at harvest time. Moreover, pesticide risk assessment for all the detected residues was conducted. A maximum 0.0012 % of acceptable daily intake (150 mg kg^?1) for national estimated daily intake indicated low dietary risk of these products.     

Dissipation of S-metolachlor in plant and soil and effect on enzymatic activities

The present study aimed at evaluating the dissipation of S-metolachlor (S-MET) at three doses in maize growing on diverse physico-chemical properties of soil. The effect of herbicide on dehydrogenase (DHA) and acid phosphatase (ACP) activity was estimated. A modified QuEChERS method using LC-MS/MS has been developed. The limit of quantification (0.001 mg kg^?1) and detection (0.0005 mg kg^?1) were very low for soil and maize samples. The mean recoveries and RSDs for the six spiked levels (0.001–0.5 mg kg^?1) were 91.3 and 5.8%. The biggest differences in concentration of S-MET in maize were observed between the 28th and 63rd days. The dissipation of S-MET in the alkaline soil was the slowest between the 2nd and 7th days, and in the acidic soil between the 5th and 11th days. DT₅₀ of S-MET calculated according to the first-order kinetics model was 11.1–14.7 days (soil) and 9.6–13.9 days (maize). The enzymatic activity of soil was higher in the acidic environment. One observed the significant positive correlation of ACP with pH of soil and contents of potassium and magnesium and negative with contents of phosphorus and organic carbon. The results indicated that at harvest time, the residues of S-MET in maize were well below the safety limit for maize. The findings of this study will foster the research on main parameters influencing the dissipation in maize ecosystems.     

Dissipation behavior and risk assessment of butralin in soybean and soil under field conditions

Dissipation behavior, final residue, and risk assessment of butralin in soybean, green soybean, plant, and soil were investigated. Butralin residues were extracted with acetonitrile and then soybean samples were detected with gas chromatography-mass spectrometer (GC-MS) and soil samples were determined with GC with nitrogen phosphorous detector (GC-NPD). The limit of quantification (LOQ) of the method was 0.01 mg/kg for soybean, green soybean, plant, and soil. Average recoveries ranged from 90.4 ~ 98.2% for green soybean, 86.2 ~ 86.6% for soybean, 86.0 ~ 98.8% for plant, and 85.0 ~ 106.8% for soil. The relative standard deviations (RSDs) were 2.0 ~ 7.2% for green soybean, 2.0 ~ 3.0% for soybean, 3.1 ~ 8.1% for plant, and 1.8 ~ 6.6% for soil. Half-lives of butralin in soil samples varied in the range of 11–22 days. At harvest time, final residues of butralin in soybean and green soybean were lower than LOQ. Risk assessment demonstrated that, at recommended dosage and frequency, butralin would not induce significant harm on humans. The study could be used as a quantitative basis for application of butralin on soybean.     

Pyrimethanil residue and dissipation in tomatoes and soil under field conditions

A residue analytical method to detect pyrimethanil in tomatoes and soil was developed by using high-performance liquid chromatography with a diode array detector. The dissipation and residue level of pyrimethanil in tomatoes and soil were also investigated. Results showed that the average recoveries are in the range of 87.2 to 90.0 % with a relative standard difference of 2.22 to 7.61 % in tomatoes and soil. In Guangdong, Shandong, and Yunnan, the half-lives of pyrimethanil in tomatoes were 1.8, 3.6, and 4.2 days and those in soil were 4.0, 3.3, and 3.9 days, respectively. The dissipation rate of pyrimethanil in tomatoes and soil was affected by temperature, precipitation, and soil type. The terminal residue results showed that when pesticide pyrimethanil was used under the experiment design, all the results were far below the available maximum residue limits. Low residues in tomatoes and soil suggest that this pesticide is safe to use under the recommended dosage.     

Dissipation kinetics of tetraconazole in three types of soil and water under laboratory condition

Laboratory experiment was conducted to understand the persistence behavior of tetraconazole in three soils of West Bengal (alluvial, red lateritic, and coastal saline) and also in water maintained at three different pH (4.0, 7.0, and 9.2) conditions. Processed soil samples (100 g) were spiked at two treatment doses: 2.5 μg/g (T₁) and 5.0 μg/g (T₂). Double distilled buffered water (200 ml) was spiked at two treatment doses: 1.0 μg/ml (T₁) and 2.00 μg/ml (T₂). The tetraconazole dissipation followed first-order reaction kinetics and the residual half-life (T _1/2) values in soil were found to be in the range of 66.9–77.2 days for T₁ and 73.4–86.0 days for T₂. The persistence increased in the order red lateritic > new alluvial > coastal saline. Interestingly, the red lateritic soil exhibited the lowest pH (5.56) and organic carbon (0.52 %) content as compared to other two soils. However, the dissipation of tetraconazole in case of water was not pH dependant. The T _1/2 values in water were in the range of 94 to 125 days. The study indicated the persistent nature of tetraconazole in soil and water.     

DDT residue in soil and water in and around abandoned DDT manufacturing factory

Dichlorodiphenyltrichloroethane (DDT) belongs to one of the most hazardous groups of chemicals called persistent organic pollutants. Many organochlorine pesticides including p,p(')-DDT are long lasting due to their non-degradability can travel to distant places and being fat soluble can accumulate in animals and human bodies. Due to the persistent nature of p,p(')-DDT, its adverse environmental and health impacts, the present study was undertaken to examine the residual p,p(')-DDT in and around abandoned p,p(')-DDT manufacturing factory in Amman Gharh, Nowshera, NWFP. Samples of soil, sediments and water were collected in and around the factory area, nearby p,p(')-DDT stores, main factory drain leading to river Kabul and nearby villages. Standard procedures were used for the collection, transportation and storage of samples for analyses. Extraction of each sample for p,p(')-DDT analyses was carried out in triplicates using Soxhelt extraction. p,p(')-DDT contents in the samples were analyzed by capillary GC with electron capture detector. Most of the samples collected up to half kilometer distance from the site of the DDT factory were found contaminated. Further the level of p,p(')-DDT decreased with increasing depth from top to bottom and with distance from the site. The results indicate that there is no immediate threat to underground water reservoirs.     

Dissipation studies of fentrazamide (YRC-2388) in soil under anaerobic condition

Dissipation of fentrazamide in soil and water under flooded (anaerobic) conditions was studied. Fentrazamide was applied to soil at 100 g ha(-1). Soil was extracted with 0.1 N HCl?:?acetone (1?:?1 v/v) followed by partition and cleanup with silica SPE. Separation was achieved in an ODS-II column with a mobile phase of acetonitrile?:?water (70?:?30 v/v) and detection at 214 nm. Recovery of fentrazamide varied from 75.2-90.4% and 89.9-97.8% in soil and water, respectively. Fentrazamide dissipated rapidly and fentrazamide residues were not detected after 100 and 35 days of application in soil and water, respectively. Half life in soil and water was 9.06 and 3.66 days, respectively. Dissipation followed monophasic first order kinetics pattern. No fentrazamide was detected in soil, rice grain and rice straw at harvest of crop. Calibration curves for quantification were linear and relative standard deviation (RSD) was 1.78%. LOD for instrument was 0.002 μg mL(-1) and LOQ for methods were 0.005 μg g(-1) for soil and water.     

土壤中有机氯农药残留分析前处理方法研究

利用硅胶柱、氟罗里土柱净化前处理方法对浙江某地区土壤样品中六六六、滴滴涕有机氯农药的残留量进行分析,并与现行的GB/T 14550-1993浓硫酸净化前处理方法进行比较。实验结果表明,采用柱净化前处理方法加标回收率在78%～121%,两种前处理方法所得气相色谱分析结果的平均相对标准偏差小于±20%,表明利用柱净化前处理方法能满足痕量有机物残留分析的要求。     

Dissipation kinetics,safety evaluation,and assessment of pre-harvest interval (PHI) and processing factor for kresoxim methyl residues in grape

A field dissipation study was conducted to evaluate the pre-harvest interval (PHI) and processing factor (PF) for kresoxim methyl (Ergon 44.3 SC) residues in grapes and during raisin making process at recommended dose (RD) and double the recommended dose (DRD). Kresoxim methyl residues dissipated following 1st-order kinetics with a half-life of 10 and 18 days at RD and DRD, respectively. The PHIs with respect to the European Union maximum residue limit (EU-MRL) of 1 mg kg^?1 for grapes were 13 and 30 days at RD and DRD, respectively. The degradation data during grape to raisin making process were best fitted to nonlinear 1st?+?1st-order kinetics with a half-life ranging between 4 and 8 days for both shade drying and with raisin dryer at different doses. The PFs were 1.19 and 1.24 with shade drying and 1.09 and 1.10 with raisin dryer, respectively, which indicates concentration of the residues during raisin making process. The dietary exposure of kresoxim methyl on each sampling day was less than the respective maximum permissible intake both at RD and DRD. The residues of kresoxim methyl in market samples of grapes and raisins were well below the EU-MRL and were also devoid of any risk of acute toxicity related to dietary exposure.     

Dissipation of cypermethrin,chlorpyriphos, and profenofos in tomato fruits and soil following application of pre-mix formulations

In this study, changes in heavy metal accumulation in U. rigida J. Agardh taxon and seawater have been investigated with respect to different stations and seasons. For this purpose, the severity of heavy metal pollution in the Dardanelles has been presented through the determination of Cu, Pb, Zn, and Cd concentrations in U. rigida macroalgae and seawater taken seasonally from the stations located on six different regions on the strait. While the metal concentrations in alga specimens were found to be high in spring and winter in all stations; the metal concentrations in the seawater, particularly the Pb concentration, were found to be high in all seasons.     

Determination and study on dissipation and residue of bismerthiazol and its metabolite in Chinese cabbage and soil

A simple and accurate method for the determination of bismerthiazol and its metabolite 2-amino-5-mercapto-1,3,4-thiadiazole was developed in Chinese cabbage and soil by high-performance liquid chromatography-diode array detection in this study. The limits of detection were 0.06 mg/kg for bismerthiazol and 0.03 mg/kg for 2-amino-5-mercapto-1,3,4-thiadiazole, respectively. Recoveries of cabbage and soil were investigated at three spiking levels and were in the range of 84.0–96.0 % for bismerthiazol and 71.0–74.6 % for 2-amino-5-mercapto-1,3,4-thiadiazole, with relative standard deviations below 7.0 %. For field experiments, the half-life of bismerthiazol was 2.4–2.5 days in Chinese cabbage and 2.5–4.8 days in soil at the two experimental locations in China. Dissipation residues of 2-amino-5-mercapto-1,3,4-thiadiazole were lower than 0.72 mg/kg. Terminal residues of bismerthiazol and its metabolite were less than 3.0 and 0.3 mg/kg in Chinese cabbage, respectively. No bismerthiazol or metabolite residues were detected in soil on days 5, 7, 10, and 14 after the last spraying at the two dosage levels.