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71.
《Biomedical chromatography : BMC》2018,32(2)
A gas chromatography–tandem mass spectrometry method was developed and validated to simultaneously determine boscalid and fludioxonil in grape and soil samples. These samples were extracted with 10 mL of acetonitrile and purified using a mixed primary secondary amine/octadecylsilane sorbent. The method showed good linearity (R2 > 0.99) in the calibration range 0.005–2 μg/mL for both pesticides. The limits of detection and quantification for the two analytes in grape and soil were 0.006 and 0.02 mg/kg, respectively. Fungicide recoveries in grape and soil were 81.18–92.11% for boscalid and 82.73–97.67% for fludioxonil with relative standard deviations of 1.31–10.31%. The established method was successfully applied to the residual analysis of boscalid and fludioxonil in real grape and soil samples. The terminal residue concentrations of boscalid and fludioxonil in grape samples collected from Anhui and Guizhou were <5 mg/kg (the maximum residue limit set by China) 7 days after the last application and 1 mg/kg (the maximum residue limit set by USA) 14 days after the last application. These results could provide guidance for the proper and safe use of boscalid and fludioxonil in grape and help the Chinese government to establish an MRL for fludioxonil in grape. 相似文献
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73.
利用“每课一题”这个教学环节从已有知识中提取基本原理,并应用于新知识的学习;提取学生的问题编制习题,让学生暴露产生问题的根源并从根本上解决。探讨了每课一题的必要性及其基本类型。 相似文献
74.
Talat Baran 《高分子科学杂志,A辑:纯化学与应用化学》2018,55(3):280-287
To maintain catalytic performance of any catalyst for a long time, the selection of support material is a very important parameter for heterogeneous catalytic systems, and this performance makes the catalyst valuable. In view of its low cost and availability, silica can be considered as a good support material for transition metal ions in the cross coupling reactions. Therefore, this study describes i) silica-gel based palladium catalyst with a long-term catalytic performance, ii) rapid, simple, economic, and green procedure which was developed for Suzuki reactions. The catalyst showed superior reusability (ten runs) and catalytic efficiency against coupling reactions under mild conditions (50°C, 5 min and air atmosphere). Moreover, the catalyst gave partially good reaction yields with aril chlorides which have poor activity in coupling reactions. In addition, an excellent turnover number (TON: 66000) and frequency (TOF: 825000) were obtained using very small catalyst loading (1.5 × 10?3 mol %). This paper concludes that silica-gel based Pd(II) catalyst and the protocol of synthesis of biaryls were suitable for coupling reactions. 相似文献
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76.
Qing-Ping Mei Yi-Ke Tang Tai-Fu Li Li-Zhong Yao Qiong Yang Heng-Jian Zhang 《Analytical letters》2018,51(8):1176-1193
The calibration model of near-infrared (NIR) spectra established using the Kalman filter-partial least square (partial least squares combined with a Kalman filter) method can be adapted to outdated equipment, environmental changes, external samples, and other applications. However, the variance of the measurement noise estimation for NIR spectrum measurements cannot be easily obtained using Kalman filter-partial least squares; therefore, the variance in the measurement noise is often assumed to be zero for the Kalman filter-partial least square calibration model, which affects the stability of the model. In this study, the measured input and output data were used effectively, and the gamma test method for estimating the measurement noise variance was used to improve the stability of the Kalman filter-partial least square calibration model. First, an accurate estimation of the measurement noise variance was obtained, and accurate modeling was then performed using Kalman filter-partial least squares. Finally, 600 abandoned drilling fluid samples were used to confirm the validity of the proposed method. The Kalman filter-partial least square and gamma test-Kalman filter-partial least square methods are compared. Testing of external samples 401–600 demonstrated that the stability of the Kalman filter-partial least square model decreased. The root mean square error of the prediction of the Kalman filter-partial least square model was 27.135, which was worse than that of the gamma test-Kalman filter-partial least square model (20.307). The validation results show that the proposed method has better stability in tracking the evolution of the NIR spectrometer’s measurement state. 相似文献
77.
Dr. Qaisar Nadeem Dr. Giuseppe Meola Dr. Henrik Braband Robin Bolliger Dr. Olivier Blacque Daniel Hernández-Valdés Prof. Dr. Roger Alberto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(3):1213-1216
The labeling of (bio)molecules with metallic radionuclides such as 99mTc demands conjugated, multidentate chelators. However, this is not always necessary since phenyl rings can directly serve as integrated, organometallic ligands. Bis-arene sandwich complexes are generally prepared by the Fischer–Hafner reaction. In extension of this, we show that [99mTc(η6-C6R6)2]+-type complexes are directly accessible from water and [99mTcO4]−, even using arenes incompatible with Fischer–Hafner conditions. To unambiguously confirm the nature of these unprecedented 99mTc complexes, their rhenium homologous have been prepared by substituting naphthalene ligands in [Re(η6-C10H8)2]+ with the corresponding phenyl groups. The ease with which highly stable [99mTc(η6-C6R6)2]+ complexes are formed under standard labeling conditions enables a multitude of new potential imaging agents based on commercial pharmaceuticals or lead structures. 相似文献
78.
Polychlorodibenzo-p-dioxins, polychorodibenzofurans and “dioxin-like” polychlorinated biphenyls are widespread persistent organic pollutants sharing a similar toxicological pathway mediated by the aryl-hydrocarbon receptor (AhR). Since the confirmatory method for their measurement at trace levels in complex matrices (using isotopic dilution and gas chromatography-high resolution mass spectrometry) remains time and cost-consuming, growing efforts of the scientific community have been focused on the development of screening approaches, including AhR mediated assays. Unfortunately, AhR ligands are highly diverse and agonistic/antagonistic effects can be observed on procedural blanks and/or sample extracts. In this study, the influence of solvent grade quality on the response of a DNA-binding AhR mediated assay used for screening dioxins has been investigated. Our results demonstrated a very critical impact of this parameter with both strong agonistic and antagonistic effects observed for any tested solvent lot. A small silver nitrate silica column removed partly these interfering compounds and then can be recommended as final purification step. Some preferable grades can be identified and selected in order to guarantee the best possible performances. However, it appears necessary to test every new lot, even if a grade appeared previously compliant. 相似文献
79.
80.
Fandong Meng Genhui Xu Baowei Wang Xinbin Ma. School of Chemical Engineering Technology Tianjin University Tianjin China . Luoyang Petrochemical Engineering Corporation Luoyang ChinaManuscript received March revised Apr 《天然气化学杂志》2002,(Z1)
This article describes a process for the synthesis of diethyl oxalate by a coupling reaction of carbon monoxide, catalyzed by palladium in the presence of ethyl nitrite. The kinetics and mechanism of the coupling and regeneration reaction are also discussed. This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation. 相似文献