Dissipation and residue fate of kresoxim-methyl in tobacco leaves and soil under field conditions

The fate of kresoxim-methyl was studied in a tobacco field ecosystem, and a simple and reliable method was developed for the determination of kresoxim-methyl in soil, green and cured tobacco leaves. Kresoxim-methyl residues were extracted from samples with petroleum ether, and determined by gas chromatography (GC) coupled with an electron capture detector (ECD). Kresoxim-methyl (30% suspension concentration) was applied at 150 g a.i. ha^–1 (the recommended high dosage) and 225 g a.i. ha^–1 (1.5 times the recommended high dosage) in the experimental fields in Huishui and Changsha in China. The limits of detection (LODs) and limits of quantification (LOQs) of kresoxim-methyl in green tobacco leaves, cured tobacco leaves and soil were 0.012 and 0.04 mg kg^–1, 0.12 and 0.4 mg kg^–1, and 0.0015 and 0.005 mg kg^–1, respectively. The average recoveries were 84.5% to 95.7%, 79.8% to 94.3% and 83.3% to 93.8% with relative standard deviations (RSDs) less than 10% in green tobacco leaves at four spiked levels (0.04, 0.2, 2 and 8 mg kg^–1), cured tobacco leaves at three spiked levels (0.4, 1 and 10 mg kg^–1) and soil at three spiked levels (0.005, 0.05 and 0.5 mg kg^–1), respectively. The results showed that the half-lives of kresoxim-methyl in green tobacco leaves and soil were 1.2–5.3 days and 6.7–10.4 days, respectively. At harvest, kresoxim-methyl residues in cured tobacco leaves samples collected 21 days after the last application at the recommended dosage were below 1.0 mg kg^–1. These results could help establish appropriate application frequency and harvest intervals in the use of kresoxim-methyl on tobacco plants.     

Analysis of triallate residue and degradation rate in wheat and soil by liquid chromatography coupled to tandem mass spectroscopy detection with multi-walled carbon nanotubes

A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method for the analysis of triallate residue in wheat and soil was developed and validated. Multi-walled carbon nanotubes were used as clean-up sorbent. The residual levels and dissipation rates of triallate in wheat and soil were determined by liquid chromatography–tandem mass spectrometry. The limit of quantification was established as 0.01, 0.02 and 0.05 mg kg^?1 for soil, wheat and wheat plant samples, respectively. The average recoveries of triallate ranged from 77% to 108% at fortified levels of 0.01–0.5 mg kg^?1 with relative standard deviations of 3.0–8.4% (n = 5). From residue trials at three geographical experimental plots in China, the results showed that the half-lives of triallate in soils were 1.13–1.63 days. For trials applied according to the label recommendation, the final residues of triallate in wheat at harvest time were all below 0.05 mg kg^?1 (the maximum residue levels of China, Japan, Korea and the US).     

Dissipation and residue of flonicamid in cucumber,apple and soil under field conditions

A method based on QuEChERS-like extraction and UPLC-ESI-MS/MS for the analysis of flonicamid was established. The samples were extracted by acetonitrile–methanol mixture and were purified using PSA. At fortification levels of 0.01, 0.1 and 0.5 mg/kg in cucumber, apple and soil, recoveries ranged from 71.5 to 106.0% with relative standard deviation (RSD) of 2.6–9.9%. The limit of quantification (LOQ) was 0.003 mg/kg for cucumber, apple and soil. This study also investigates the dissipation of flonicamid in cucumber, apple and soil. The dissipation half-lives of flonicamid in cucumber, apple and soil were 3.0–4.9 days, 5.1–6.1 days and 10.3–14.2 days, respectively. The final residues of flonicamid ranged from 0.029 to 0.295 mg/kg in cucumbers, <0.01–0.174 mg/kg in apples and <0.01–0.172 mg/kg in soil, respectively. The observed low residual levels of flonicamid suggest that the cucumber and apple are safe when applied at the recommended dosage.     

Determination and study on residue and dissipation of benazolin-ethyl and quizalofop-p-ethyl in rape and soil

A QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for the determination of benazolin-ethyl and quizalofop-p-ethyl in rape and soil by high-performance liquid chromatography-tandem mass spectrometry has been developed in this study. The residue and dissipation of benazolin-ethyl and quizalofop-p-ethyl in rape and soil were determined with the developed method. The half-lives of benazolin-ethyl in rape straw and soil were 3.7–5.1 days and 14.3–26.3 days, respectively. The half-lives of quizalofop-p-ethyl in rape straw and soil were 5.0-6.1 days and 0.3–9.7 days, respectively. The residue of benazolin-ethyl and quizalofop-p-ethyl in rapeseed and soil were below the detection limit (i.e., 0.5?mg?kg^?1, the maximum residue level of European Union for quizalofop-p-ethyl).     

Simultaneous determination of thiamethoxam and its metabolite clothianidin by LC-MS/MS in goji berry and soil

In this study, an effective analytical method for simultaneous determination of thiamethoxam and its metabolite clothianidin in goji berry and soil was developed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The recoveries of the compounds in goji berry and soil at the levels of 0.005, 0.02, and 0.1 μg kg^?1 were 84.7–98.9% and the relative standard deviations (RSDs) were 0.9–3.2%. The limits of detection (LOD) for both compounds in goji berry and soil matrices were 0.001 mg kg^?1; the limits of quantification (LOQ) were 0.005 mg kg^?1 for both compounds in two matrices. The dissipation and final residual experiments in 2016 with the commercial formulation of dinotefuran ? thiamethoxam 30% suspension concentrate (SC) was conducted in goji berries in northwest China (Qinghai, Gansu, Inner Mongolia, and Ningxia). Thiamethoxam was dissipated fast in goji plant ecosystem with half-lives were 1.08–1.01 and 2.04–4.25 days in goji berry and soil. The final residues of thiamethoxam were <0.005–0.382 and <0.005–1.120 mg kg^?1 in goji berry and soil, respectively.     

Dissipation,residue, and distribution of pyraclostrobin in banana and soil under field conditions in South China

Two independent field trials were conducted in Guangdong and Guangxi, South China, in 2013, to study the dissipation, residue levels, and distribution of pyraclostrobin in banana and soil under field conditions. Pyraclostrobin residues were determined through a quick and effective method of high-performance liquid chromatography. Results showed that the average recoveries ranged from 80.55% to 98.08%, with relative standard deviations of 3.18–7.81% at three different spiking levels for each different matrix. The quantification limit of the proposed method was 0.006 mg/kg for both banana and soil. The half-lives of pyraclostrobin in bananas were 9.09 days in Guangdong and 8.26 days in Guangxi, and both bananas exhibited a dissipation rate of 90% after 28 days. The half-lives of pyraclostrobin in soil were 11.61 days in Guangdong and 10.60 days in Guangxi, with a dissipation rate of 90% after 35 days. Although several positive banana samples (i.e., pyraclostrobin exceeding the maximum residue limits (MRL) were found, the terminal residues in banana pulp were not detectable. All the terminal residues in banana pulp were below the MRL of 0.02 mg/kg, set by the Chinese Ministry of Agriculture, indicating a negligible risk associated with the exposure to pyraclostrobin via the consumption of banana. The distribution of pyraclostrobin in soil was also investigated in two experimental sites. The pyraclostrobin in different layer soil was time dependent and did not vary between the two sites. The result also showed that pyraclostrobin could be easily transported from the top soil to the subsoil. However, the highest quantity ratio did not exceed 10% in the bottom layer (20–30 cm). The distribution assessment also revealed that no significant potential environment risk was induced by pyraclostrobin in bananas.     

气相色谱法测定茶叶及土壤中的高效氯氟氰菊酯残留量

建立了气相色谱测定茶叶及土壤中高效氯氟氰菊酯残留量的分析方法。茶叶和土壤样品用正己烷提取,毛细管柱分离,气相色谱-电子捕获检测器(GC-ECD)检测。结果表明: 在高效氯氟氰菊酯添加量为0.02～2.00 mg/kg范围内,高效氯氟氰菊酯在鲜茶叶和土壤中的平均添加回收率分别为89.0%～94.1%和89.8%～94.7%,相对标准偏差(RSD, n=5)分别为3.0%～4.9%和2.5%～4.2%,方法的最低检出限(S/N=3)为0.002 mg/kg。采用该方法测定2.5%高效氯氟氰菊酯微乳剂在湖南长沙茶叶及土壤中的消解动态,其符合一级动力学消解模式,消解方程分别为y=3.1996e-0.3394x和y=0.1224e-0.1036x,相关系数分别为0.9956和0.9247。在茶叶中的半衰期为2.04 d,在土壤中的半衰期为6.69 d。该方法为湖南长沙地区茶叶种植科学合理地使用杀虫剂高效氯氟氰菊酯提供了依据。     

Fate of hexaconazole and isoprothiolane in rice,soil and water under field conditions

Residue dissipation of hexaconazole and isoprothiolane in the rice field ecosystem was determined by gas chromatography coupled with electron capture detector. Hexaconazole and isoprothiolane (33% microemulsion) were applied at two dosages, 396 g a.i. ha^–1 (the recommended dosage) and 594 g a.i. ha^–1 (1.5 times the recommended dosage) in the experimental fields in Guizhou, Hunan and Heilongjiang provinces, China, during 2011–2012. The limits of detection and limits of quantification in brown rice were 0.006 and 0.02 mg kg^–1 for hexaconazole, 0.0072 and 0.024 mg kg^–1 for isoprothiolane, respectively, and they were much below the maximum residue limits (MRLs, 0.1 mg kg^–1 for hexaconazole and 1.0 mg kg^–1 for isoprothiolane) set by China. Average recoveries of hexaconazole in water, soil, rice plants and brown rice ranged from 77.3% to 93.8% and for isoprothiolane ranged from 78.1% to 99.9% with relative standard deviations < 10%. The results showed that during harvest, the terminal residue levels of hexaconazole and isoprothiolane in brown rice samples were well below the MRLs of China following the interval of 7 days after last application. Therefore, a dosage of 396 g a.i. ha^–1 was recommended, which could be considered as safe to human beings.     

Residues and dissipation of chlorothalonil and azoxystrobin in cabbage under field conditions

Chlorothalonil and azoxystrobin, as efficient and broad-spectrum fungicides, are two widely used fungicides to control downy mildew and anthracnose on cabbage. For the safe and rational use of these two pesticides on cabbage, their residues and dissipation were studied under field conditions. The trial results showed that chlorothalonil and azoxystrobin residues were affected by the frequency and dosage of application, and the weather condition post-application. Chlorothalonil and azoxystrobin dissipated rapidly in cabbage with the mean half-live of 1.7 and 0.4 days at three geographical experimental plots in China, respectively. The terminal residues of chlorothalonil and azoxystrobin in cabbage at harvest time were all below the maximum residue limit (MRL, 6 mg kg^?1 for chlorothalonil and 5 mg kg^?1 for azoxystrobin) established by Codex Alimentarius Commission. It suggested that this formulation of chlorothalonil and azoxystrobin (560 g L^?1, SC) may be safer under the recommended dosage. Given that in China no MRL has been set for chlorothalonil and azoxystrobin in cabbage, this study could provide a guidance for establishing MRL, and the safe and rational use of these two pesticides.     

QuEChERS法提取水稻土壤中的五氯酚

用超声振荡与一种快速、简易、廉价、高效、可靠、安全的分离方法(简称QuEChERS)法相结合的技术研究水稻土壤中五氯酚的提取。就萃取剂、酸用量、提取方式、吸附剂种类以及吸附剂用量等因素对回收效率的影响作了比较。结果表明,最佳条件为:用10mL乙腈为提取液,2mL浓度为6mol/L的H2SO4酸化,加2mL正己烷,振荡30min,40℃超声1h,离心后上清液再选用20mgODS和200mg无水硫酸镁净化。在高、中、低3个不同浓度的土壤中,都可以稳定在75%～120%的回收率。     

Determination and dynamics of kanamycin A residue in soil by HPLC with SPE and precolumn derivatization

As one of the aminoglycoside antibiotics, kanamycin has been widely used in human therapy and as an additive to promote growth and prevent disease in forage. The kanamycin residue may have potenital risks for organisms and the environment. Therefore, the monitoring of this drug may have dynamic importance. In this work, a novel method for determination and dynamic study of kanamycin A was developed through solid phase extraction and derivatization with 4-chloro-3,5-dinitrobenzotrifluoride before high-performance liquid chromatography analysis. The calculated recoveries were from 72.3 to 92.5%, with relative standard deviations from 2.99 to 6.94%. The detection limit of kanamycin A in soil was 0.006?mg?kg^?1 with a signal-to-noise ratio of 3. The dynamics in soil showed that the degradation of kanamycin A coincided with the equations C?=?1.951e^{?0.0482 t} for black soil and C?=?1.807?e^{?0.0247 t} for red soil and the half-lives were 14.38 and 28.06?d respectively. The degradation rate reached 95.19% in black soil after 63 days compared with 77.14% in red soil.     

Determination of Prometryne in water and soil by HPLC-UV using cloud-point extraction

A CPE-HPLC (UV) method has been developed for the determination of Prometryne. In this method, non-ionic surfactant Triton X-114 was first used to extract and pre-concentrate Prometryne from water and soil samples. The separation and determination of Prometryne were then carried out in an HPLC-UV system with isocratic elution using a detector set at 254 nm wavelength. The parameters and variables that affected the extraction were also investigated and the optimal conditions were found to be 0.5% of Triton X-114 (w/v), 3% of NaCl (w/v) and heat-assisted at 50 °C for 30 min. Using these conditions, the recovery rates of Prometryne ranged from 92.84% to 99.23% in water and 85.48% to 93.67% in soil, respectively, with all the relative standard deviations less than 3.05%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.5 μg L⁻¹ and 11.0 μg L⁻¹ in water and 4.0 μg kg⁻¹ and 13.0 μg kg⁻¹ in soil, respectively. Thus, we developed a method that has proven to be an efficient, green, rapid and inexpensive approach for extraction and determination of Prometryne from soil samples.     

Dissipation dynamics of fenamidone and propamocarb hydrochloride in pepper,soil and residue analysis in vegetables by ultra-performance liquid chromatography coupled with tandem mass spectrometry

In this study, a rapid and sensitive method was developed for determining fenamidone and propamocarb hydrochloride residues in vegetables and soil by ultra-performance liquid chromatography-tandem mass spectrometry. The dissipation dynamics of fenamidone and propamocarb hydrochloride in pepper and soil was investigated in Beijing, Henan and Shandong provinces. The target compounds were extracted with methanol and cleaned with dispersive solid phase extraction using primary secondary amine. Two pairs of precursor product ion transitions for fenamidone and propamocarb hydrochloride were measured and evaluated. Average recoveries of fenamidone in potato, tomato, cabbage, pepper and soil at three levels (10, 100 and 1000 μg kg^?1) ranged from 76.91% to 107.31% with relative standard deviations (RSDs) from 2.74% to 10.87% (n = 15). The average recoveries of propamocarb hydrochloride ranged from 74.84% to 97.96% with RSDs from 2.43% to 16.16% (n = 15). The limits of detection (LODs) for fenamidone in each matrix were 0.131–0.291 μg kg^?1, and the limits of quantification (LOQs) were 0.436–0.970 μg kg^?1. The LODs for propamocarb hydrochloride were 0.125–0.633 μg kg^?1, and the LOQs were 0.417–2.11 μg kg^?1. The results also showed that the dissipation of fenamidone and propamocarb hydrochloride in pepper and soil followed first-order kinetics model more than that of bi-exponential models. The half-lives of propamocarb hydrochloride were 6.90–15.78 days in pepper and 13.56–23.02 days in soil. The half-lives of fenamidone were 7.48–11.29 days in pepper and 35.18–42.78 days in soil.     

QuEChERS净化GC/ECD测定茶叶与土壤中噻虫嗪、虫螨腈及高效氯氟氰菊酯残留

采用QuEChERS方法净化,建立了GC/ECD法同时检测茶叶和土壤中噻虫嗪、虫螨腈和高效氯氟氰菊酯残留的分析方法。样品经水浸润后,乙腈提取,适量PSA、GCB和Florisil混合填料净化提取液,GC/ECD检测。噻虫嗪、虫螨腈和高效氯氟氰菊酯的响应分别在0.50～400、0.20～100、0.40～200μg/L质量浓度范围内线性良好,相关系数r均大于0.99,检出限分别为0.25、0.05、0.10μg/L。茶叶和土壤样品中,噻虫嗪、虫螨腈和高效氯氟氰菊酯的平均加标回收率为62%～108%,相对标准偏差(RSDs)不大于15.8%,方法的定量下限(LOQs)均不大于10μg/kg。方法简便、快速,能够满足茶叶和土壤中上述3种不同极性农药残留同时检测的需要。采用该方法测定了3种农药在茶园茶叶和土壤中的残留量,结果满意。     

Residue and dissipation of zinc thiazole in tobacco field ecosystem

A high-performance liquid chromatography with ultraviolet (HPLC-UV) detection method after derivatisation was developed for the first time for the novel fungicide zinc thiazole residue in tobacco samples. Field trials in two different locations were conducted to investigate the dissipation and residue of zinc thiazole in tobacco leaves and soil. The average recoveries of zinc thiazole were in the range of 82.5%–93.9% with relative standard deviations (RSDs) of 1.2%–9.1%. The zinc thiazole showed a rapid dissipation rate in fresh tobacco leaves with the half-lives of 1.1–1.6 days. The terminal residues of zinc thiazole in cured tobacco leaves and soil were 2.8–28.0 mg kg^?1and <0.05 mg kg^?1, respectively. The results could be used to establish the maximum residue limits (MRLs) and provide guidance for the scientific use of zinc thiazole in agriculture.     

高效液相色谱法测定柑橘和土壤中残留的多菌灵

建立了柑橘和土壤中多菌灵残留量的高效液相色谱(HPLC)分析方法。柑橘果肉、果皮、全果和土壤样品中残留的多菌灵用碱性乙腈溶液提取,经NH2固相萃取(SPE)柱净化,HPLC分离,紫外检测器检测,外标法定量。在0.02～5.0 mg/L范围内,多菌灵的峰面积与其质量浓度呈良好的线性关系,相关系数为0.9997。柑橘果肉、果皮、全果和土壤中添加0.05～0.5 mg/kg多菌灵标准品的平均回收率为89.2%～102%,相对标准偏差为1.8%～9.1%;柑橘果肉和土壤中多菌灵的最低检测浓度为0.05 mg/kg,柑橘果皮和全果中多菌灵的最低检测浓度为0.1 mg/kg。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求。     

Dissipation and residue behaviour of oryzalin in grape ecosystem using RRLC-QqQ-MS/MS

The dissipation and terminal residues of oryzalin in grape ecosystem under open-field condition were investigated at two different locations, Beijing and Shandong in China. Residues in field-treated samples were determined by a sample method using rapid resolution liquid chromatography triples quadrupole tandem mass spectrometry (RRLC-QqQ-MS/MS). This method showed satisfactory qualitative and quantitative performance. The mean recoveries of oryzalin at different fortification levels (0.01, 0.1 and 1 mg/kg for grape; 0.01, 0.1, 1, 10 and 30 mg/kg for soil) ranged from 88.2% to 98.8%, with the relative standard deviations ≤4.9%. The limits of detection and quantification were, respectively, 0.003 and 0.01 mg/kg. In soil, the dissipation half-lives were about 9 days and the terminal residues ranged from <0.01 to 0.58 mg/kg in both Beijing and Shandong. The concentrations of oryzalin in grapes were lower than 0.01 mg/kg in most of the samples of dissipation study and all the samples of residue study. As far as we know, this is the first study focusing on the dissipation and terminal residue of oryzalin in grape ecosystem, and no maximum residue limits (MRLs) of oryzalin in grapes were recommended by China, Codex Alimentarius Commission or European Union . Therefore, these data not only provide important information about the fate and residues of oryzalin in grape ecosystem, but also could be very useful for the establishment of the MRLs of oryzalin in grapes.     

QuEChERS-高效液相色谱检测土壤中的吡虫啉

建立了测定土壤中吡虫啉的方法。土壤样品以乙酸-乙腈(体积比为0.1∶100)溶液提取,分散固相萃取净化,乙腈-水为流动相(体积比为7∶13),流速0.9 mL/min,270 nm检测,外标法定量。方法的线性范围为0.1~50μg/mL,线性相关系数为0.9994。平均加标回收率为90.1%~94.5%,RSD为0.7%~4.9%(n=6)。方法检测限为0.001 mg/kg(以信噪比为3计),定量限为0.004 mg/kg(以信噪比为10计)。该方法可用于新建房屋白蚁预防土壤化学屏障中吡虫啉的检测。     

Dissipation dynamics of fenoxaprop-p-ethyl and fenoxaprop acid under Indian rice field conditions

Dissipation dynamics of fenoxaprop-p-ethyl (FPPE) and fenoxaprop acid (FPA) (metabolite) in rice field conditions was investigated for two consecutive seasons. FPPE dissipated rapidly in soil with average half life of 1.42–2.19 days. Dissipation followed first-order kinetics. The method was validated in terms of accuracy, linearity, specificity and precision. Linearity was in the range of 0.005–5 µg mL^?1 with limit of detection as 0.002 and 0.001 µg mL^?1 for fenoxaprop-p-ethyl and fenoxaprop acid, respectively. Quantitation limit in soil, grain, straw and husk were 0.005, 0.008, 0.01 and 0.01 µg g^?1 for fenoxaprop-p-ethyl, and 0.005, 0.01, 0.01 and 0.01 µg g^?1 for fenoxaprop acid, respectively. Recovery in soil, rice grains, straw and husk ranged from 81.60–93.40, 77.85–87.00, 75.20–84.40 and 76.00–87.20% for FPPE and 82.50–88.20, 76.25–83.00, 74.80–83.60 and 75.00–85.40% for FPA, respectively. Below detectable limit of residues of FPPE and metabolite were observed in soil, rice grain, husk and straw samples at harvest. FPPE and FPA were of short persistence under field conditions and residues were below European Union-Maximum Residue Limits in all matrices that would cause adverse effect on environment and human/animal health.     

一种新型的杀螟丹分析方法及其在稻田杀螟丹残留动态分析中的应用

建立了一种水稻植株、糙米、稻壳、土壤和田水中的杀螟丹气相色谱-火焰光度检测(GC-FPD)方法。样品中的杀螟丹使用稀盐酸提取,然后在碱性条件下使用氯化镍(NiCl₂)将其衍生为沙蚕毒素,最后采用在线连接的支撑液液萃取(SLE)和固相萃取(SPE)进行萃取和富集。在优化好的条件下,杀螟丹在5种空白样品中低、中、高3种添加浓度的回收率为80.0%~114.4%,相对标准偏差(RSD)小于13.7%,表明所建立的方法具有良好的准确度和精密度。将所建立的方法用于大田条件下杀螟丹的残留动态分析,为建立杀螟丹的最大残留限量(MRL)提供参考,同时也可对农药施用技术的安全性进行评价。