Analysis of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction combined with gas chromatography

A novel method was developed for the determination of captan, folpet, and captafol in apples by dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD). Some experimental parameters that influence the extraction efficiency, such as the type and volume of the disperser solvents and extraction solvents, extraction time, and addition of salt, were studied and optimized to obtain the best extraction results. Under the optimum conditions, high enrichment factors for the compounds were achieved ranging from 824 to 912. The recoveries of fungicides in apples at spiking levels of 20.0 μg kg⁻¹ and 70.0 μg kg⁻¹ were 93.0–109.5% and 95.4–107.7%, respectively. The relative standard deviations (RSDs) for the apple samples at 30.0 μg kg⁻¹ of each fungicide were in the range from 3.8 to 4.9%. The limits of detection were between 3.0 and 8.0 μg kg⁻¹. The linearity of the method ranged from 10 to 100 μg kg⁻¹ for the three fungicides, with correlation coefficients (r ²) varying from 0.9982 to 0.9997. The obtained results show that the DLLME combined with GC–ECD can satisfy the requirements for the determination of fungicides in apple samples. Figure Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD) allows satisfactory determination of fungicides in apple samples     

有机催化不对称Mannich反应

有机催化的不对称合成反应是目前研究最为活跃的领域之一.不对称Mannich反应是合成光学活性β-氨基羰基化合物的有效手段.目前报道的催化不对称Mannich反应的有机催化剂主要有脯氨酸及其衍生物、手性磷酸、手性(硫)脲和金鸡纳碱衍生物等,取得了良好的催化活性和对映选择性.本文评述了各类有机催化剂在有机催化不对称Mannich反应中的应用研究进展,以及不对称诱导反应的机理、催化剂分子结构及反应条件对其催化活性和不对称诱导作用的影响.     

半平面问题远域辐射阻尼的时域边界元法模拟研究

辐射阻尼在岩石基坑爆破开挖、边坡稳定、结构抗震以及结构-地基动力相互作用等实际工程问题中具有重要意义.为了模拟半平面问题的远域辐射阻尼,以时域边界元法(TD-BEM)理论为基础,根据应力波在弹性介质中的传播特性,在时域内提出了一种新的单元,即自适应半无限边界单元,专门用于离散远域半无限边界.该单元外侧节点是一个始终处于应力波波前位置的动态节点,保证计算区域在任何情况下都恰好包含应力波的影响范围,从而模拟远域辐射阻尼.最后,分别采用近场和远场动力荷载作用下的弹性半平面算例进行验证,并将结果与有限元法FEM和常规TD-BEM结果进行综合对比.结果 表明,采用自适应半无限单元的TD-BEM满足半无限域的辐射条件,较好地解决了远域辐射阻尼的模拟问题,且在计算时间成本与常规TD-BEM几乎相同的前提下,具有更高的计算精度.     

微波辐射下离子液体催化一锅三组分反应合成3-{1-[2-(4-芳基噻唑-2-基)亚肼基]乙基}香豆素

在微波辐射下,以酸性离子液体甲基咪唑丙磺酸-三氟乙酸为催化剂,利用一锅法由乙酰香豆素、氨基硫脲和α-溴代芳乙酮三组分反应合成了系列3-{1-[2-(4-芳基噻唑-2-基)亚肼基]乙基}香豆素,反应时间短,操作简便,收率高(85%～95%),催化剂可回收循环使用,对环境友好.     

γ‐Irradiation Degradation of Methamidophos

The irradiation degradation of methamidophos in aqueous solutions by ⁶⁰Co‐γ rays was investigated. The effects of absorbed doses, saturated gas, and the additive of H₂O₂ on the degradation were also studied. The results showed that the oxidative radical, such as ·OH, played an important role in the irradiation degradation of methamidophos; while the reductive radicals, e^?_aq and ·H, had no contribution to the degradation. The degradation rate of methamidophos increased with the increase of the irradiation dosage. At certain irradiation dosage, methamidophos could be degraded completely. The degradation rate of methamidophos in the solution saturated with oxygen was higher than those saturated with other gases, which reached 100% when the absorbed dose was 8 kGy. H₂O₂ degraded methamidophos slowly when it was used alone, but could accelerate the degradation obviously when it was used with irradiation together.     

Novel method for the determination of five carbamate pesticides in water samples by dispersive liquid-liquid microextraction combined with high performance liquid chromatography

A novel method for the determination of five carbamate pesticides(metolcarb,carbofuran,carbaryl,isoprocard and diethofencard)in water samples was developed by dispersive liquid-liquid microextraction(DLLME)coupled with high performance liquid chromatography-diode array detector(HPLC-DAD).Some experimental parameters that influence the extraction efficiency were studied and optimized to obtain the best extraction results.Under the optimum conditions for the method,the calibration curve was linear in the c...     

金银花道地品与非道地品的FTIR光谱研究

利用FTIR光谱法分析了四个不同产地金银花的红外光谱图,对道地品(河南)和非道地品金银花进行了对比研究。结果表明,由于产地不同,其所含主要有效成分间的相对含量有所改变,反映在FTIR谱图上的吸收峰频率和形状都有所差异。四川产金银花与道地品的谱图从波数和吸收峰形状上都有较明显的差异,虽然山东产金银花与道地金银花齐名,但红外谱图也稍有差异。河北与山东产金银花谱图基本一致。道地品在1 734 cm-1处有一弱吸收,山东、河北两地在此处几乎无吸收;在1 522 cm-1处,道地品是一组弱小的吸收组峰,其他产地的吸收峰为强度略强的独立峰或分裂峰;在1 155～1 045 cm-1范围内,道地品的峰形较尖窄,山东、河北的吸收峰是较宽平的分裂峰。因此,利用FTIR光谱法不仅能快速、准确地鉴别道地药材,而且还可以用来监控药材的引种栽培,优良品种的提纯复壮。     

动力学分光光度法测定中药对超氧阴离子自由基的清除率

建立了一种利用动力学分光光度法测定中药对超氧阴离子自由基清除率的新方法。研究表明：当波长为520 nm、黄嘌呤氧化酶浓度为4×10-3 μg·mL-1,反应时间在2～7 min时,可得到最佳测定条件。在该条件下测得的抗坏血酸对超氧阴离子自由基的清除率与文献报道值一致。方法用于中药厚朴和杜仲的测定,它们对超氧阴离子自由基的IC₅₀分别为7.580和323.800 mg·L-1。     

Invariant sub-manifolds and modes of nonlinear autonomous systems

I.IntroductionIntheengineeringanalysis,themethodsoflinearmodeexpansionareusedtoapproximatethemotionofthenonlinearsystems(suchastheGalerkinmethods).Becauseoflackinggrounds,theresultsarenotreliable.Forthisreason,thestudiesofnonlinearmodesarouseconsiderableinterests.Buttherearemanydifficultiescausedbyitscomplexity.Manyscentistsandengineerspayattentiontothedefinitionandcomputationofnonlinearmodesthathavenotbeensolvedcompletely.Inthe60's,Rosenbergputforwardadefinitionofnonlinearmodesforconservati…     

Synthesis,Crystal Structure and Anti-TMV Activity of(Z)-4-[3-(4-Methyl-1,2,3-thiadiazol-5-yl)-3-(4-trifluoromethylphenyl)acryloyl]morpholine

The target compound(Z)-4-[3-(4-methyl-1,2,3-thiadiazol-5-yl)-3-(4-trifluoromethylphenyl)acryloyl]morpholine was synthesized by the nucleophilic substitution,Horner-Emmons reaction,ester hydrolysis,and condensation.Its structure was characterized by NMR,H RMS and single-crystal X-ray diffraction.The crystal of the target compound belongs to monoclinic system,space group P2₁ with a=11.5058(15),b=6.6626(10),c=23.184(3)?,V=1777.3(4)?³,Z=8,D_c=1.496 Mg/m³,F(000)=792 andμ=0.229 mm^–1.X-ray analysis indicated C–H....O intermolecular H-bonds in this crystal structure.The target compound exhibited 53%curative activity against TMV.