Dissipation Behavior and Acute Dietary Risk Assessment of Thiamethoxam and Its Metabolite Clothianidin on Spinach

Thiamethoxam and its metabolite clothianidin residues pose a potential threat to human health. This study aims to investigate the residue behavior and acute dietary risk assessment of thiamethoxam and clothianidin on spinach. Thiamethoxam and clothianidin were extracted using a quick, easy, cheap, effective, rugged, safe (QuEChERS) method and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). At spike levels from 0.01 to 5 mg kg⁻¹, the average recoveries of both analytes were in the range of 94.5–105.5%, with relative standard deviations (RSDs) of 3.8–10.9%. The dissipation behavior of thiamethoxam followed first-order kinetics, with half-lives of ≤1.6 days. Clothianidin appeared readily as a plant metabolite with highest level exhibited during 3 to 5 days after application. Temperature and light may be two main factors for degradation of thiamethoxam. Besides, acute risk assessment of thiamethoxam and clothianidin was evaluated with risk quotients (RQs) <100%, which suggested a low health risk for all consumer groups of Chinese residents.     

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。     

Simultaneous determination of residues of thiamethoxam and its metabolite clothianidin in tobacco leaf and soil using liquid chromatography‐tandem mass spectrometry

A simple analytical method was developed to simultaneously determine thiamethoxam and its metabolite, clothianidin, in fresh tobacco leaf, soil and cured tobacco leaf using liquid chromatography with tandem mass spectrometry. Thiamethoxam and clothianidin in tobacco and soil samples were extracted with acetonitrile containing 0.1% formic acid and purified using an NH₂‐SPE column. The optimized method provided good linearity with coefficients of determination R² ≥ 0.9981. The limits of detection and quantification were between 0.006–0.12 and 0.02–0.4 mg/kg, respectively. Intra‐ and inter‐day recovery assays were used to validate the established method. The average recoveries of thiamethoxam and clothianidin in fresh tobacco leaf, soil and cured tobacco leaf were 75.04–100.47%, 75.86–86.40% and 89.83–99.39%, respectively. The intra‐ and inter‐day relative standard deviations were all <9%. The developed method was successfully applied for the analysis of thiamethoxam and clothianidin residues in actual tobacco and soil samples. The results indicated that the established method met the requirements for the analysis of trace amounts of thiamethoxam and clothianidin in fresh tobacco leaf, soil and cured tobacco leaf.     

Occurrence of neonicotinoids in guttation liquid of maize – soil mobility and cross-contamination

Movement of clothianidin (CLO) and thiamethoxam (TMX) applied as maize seed dressing or pre-emergence spray application was determined in different soil types. Uptake of these neonicotinoids in plants emerging from coated or non-coated seeds was characterised via guttation liquid measurements. Applied in spray at a recommended dosage of 16.5 µmol/L, TMX and CLO occurred in the guttation liquid at peak concentrations of 1.82 and 1.63 mg/L, respectively, in plants in sandy soil and at 20–40% lower levels in plants in clay or loam soils. Peak emergence was substantially higher (above 100 mg/L) in the guttation liquid of plants emerging from neonicotinoid-coated seeds at dosages of 4.87 and 2.07 µmol per seed for CLO and TMX, respectively, strongly influenced by soil type. CLO and TMX levels in plants emerging from non-coated seeds in the proximity of neonicotinoid-coated seeds were demonstrated: cross-contamination may occur by uptake through soil from neighbouring plants. CLO appeared in the guttation liquid of plants emerging from non-coated seeds in proximity to coated ones at a peak concentration (approximately 53 mg/L) in 15 days corresponding to one-fifth of the levels in plants emerging from CLO-coated seeds; CLO concentrations gradually decreased to the same levels (6.6 ± 0.3 mg/L) after 24 days. A similar trend was observed for non-coated seeds near TMX-coated ones, with a gradual increase of TMX in 17–18 days, the levels in the guttation liquid of plants emerged from non-coated seeds (approximately 123 mg/L) corresponding to two-thirds of the levels in plants emerging from TMX-coated seeds. TMX concentrations dropped to the same levels in plants emerging from non-coated and coated seeds by day 20, and CLO occurred as a metabolite. To our knowledge, this is the first scientific record of neonicotinoid levels in guttation liquid of plants emerged from non-coated maize seeds.     

高效液相色谱法检测噻虫嗪-氟虫腈悬浮剂

采用高效液相色谱法测定农药复合制荆120 g/L噻虫嗪-60 g/L氟虫腈悬浮荆.采用ODS C18反相色谱柱(150 mm×4. 6 mm i. d. ,5μm),乙腈一水(体积比为4∶6)为流动相,用紫外检测器在240 nm波长下,对试样中的噻虫嗪和氟虫腈进行分离和定量检测.噻虫嗪、氟虫腈的平均回收率分别为99. 0%～102. 0%、96. 0%～104. 0%,测定结果的相对标准偏差分别为0. 5%、1. 6%(n=6).     

Development and validation of a fully automated online-SPE–ESI–LC–MS/MS multi-residue method for the determination of different classes of pesticides in drinking,ground and surface water

The present work describes a fully automated method based on online solid phase extraction–liquid chromatography–tandem mass spectrometry for the determination of different classes of pesticides, including acidic and polar pesticides and six thiamethoxam metabolites. Sample preconcentration was performed by extracting 4 mL of the sample with a single styrene-divinylbenzene polymer. Elution of the compounds was done within the high performance liquid chromatography gradient and tandem mass spectrometry determination was performed in the selected reaction monitoring mode, by recording 1–3 transitions per compound. The overall pretreatment and analysis time per sample was less than 15 min. Method validation was performed in drinking, ground and surface water. For nearly all compounds a recovery between 70% and 120% could be achieved. The limit of detection ranges from 1.2 to 18 ng/L in drinking water and 3.0 to 23 ng/L in ground and surface water. The correlation coefficients for a calibration range of 0.05–2 µg/L are between 0.9915 and 0.9999. The limit of quantification (LOQ) for all compounds lies below the required limit of 0.1 µg/L, to fulfil the Council Directive 98/83/EC. Most of the compounds easily reach an LOQ below 0.05 µg/L.     

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.