Investigation on the thermal decomposition and flame retardancy of wood treated with a series of molybdates by TG–MS

A flame-retardant wood was prepared using a series of insoluble molybdates through the double bath technique. The flame retardancy of the wood samples was studied with the limiting oxygen index (LOI) method. The relationships between the flame-retardant performance and the thermal property of wood were studied by the thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), scanning electron microscopy (SEM), and the thermogravimetry–mass spectrometry (TG–MS) analysis methods. The results showed that the insoluble molybdates, which were precipitated into the wood by the double bath technique, can obviously improve the flame retardancy of wood. Similarly, the transition metal molybdates showed higher flame-retardant efficiency than the main group metal molybdates do, which probably due to the thermal barrier effect that Fe₂(MoO₄)₃ acts during the combustion of the samples. At the same time, Fe₂(MoO₄)₃ catalyzed the dehydration and carbonization reactions of wood, and caused an increase in the amount of char produced, and an improvement of the stability of the char residue. Moreover, the mass spectrometry results indicated that the excess transition metal ions speed up the deep decomposition of the char residue, and resulting in the smoldering of wood.     

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography-DAD detection for the determination of sulfonylurea herbicides in water samples

A new method for the determination of four sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl and chlorimuron-ethyl) in water samples was developed by dispersive liquid–liquid microextraction coupled with high performance liquid chromatography-diode array detector. Parameters that affect the extraction efficiency, such as the kind and volume of the extraction and disperser solvent, extraction time and salt addition, were investigated and optimised. Under the optimum conditions, the enrichment factors were in the range between 102 and 216. The linearity of the method was obtained in the range of 1.0–100 ng mL^?1 with the correlation coefficients (r) ranging from 0.9982 to 0.9995. The method detection limits were 0.2–0.3 ng mL^?1. The proposed method has been successfully applied to the analysis of target sulfonylurea herbicides in river, stream and well water samples with satisfactory results.     

Graphene-based solid-phase extraction combined with flame atomic absorption spectrometry for a sensitive determination of trace amounts of lead in environmental water and vegetable samples

Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using a column packed with graphene as sorbent was developed for the preconcentration of trace amounts of lead (Pb) using dithizone as chelating reagent prior to its determination by flame atomic absorption spectrometry. Some effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 10.0–600.0 μg L⁻¹ with a detection limit of 0.61 μg L⁻¹. The relative standard deviation for ten replicate measurements of 20.0 and 400.0 μg L⁻¹ of Pb were 3.56 and 3.25%, respectively. Comparative studies showed that graphene is superior to other adsorbents including C18 silica, graphitic carbon, and single- and multi-walled carbon nanotubes for the extraction of Pb. The proposed method was successfully applied in the analysis of environmental water and vegetable samples. Good spiked recoveries over the range of 95.3–100.4% were obtained. This work not only proposes a useful method for sample preconcentration, but also reveals the great potential of graphene as an excellent sorbent material in analytical processes.     

Brnsted酸性离子液体催化3,4-二氢嘧啶-2-酮衍生物的合成

以Brnsted酸性离子液体3-甲基咪唑丙烷磺酸-三氟乙酸作为催化剂,无溶剂条件下由芳香醛、乙酰乙酸乙酯和尿素合成了系列3,4-二氢嘧啶-2-酮衍生物.沸水浴中反应30～40 min,产物产率在81%～94%之间.该方法具有反应时间短、收率高、催化剂可回收重复使用等优点.产物结构经1H NMR,IR确证.     

超高效液相色谱-四极杆飞行时间质谱快速检测动物饲料中10种违禁精神药物

建立了测定动物饲料中三唑仑、艾司唑仑、硝西泮、地西泮、异丙嗪、氯氮平、唑吡坦、甲硫哒嗪、氯丙嗪和咪达唑仑10种违禁精神药物的超高效液相色谱-四极杆飞行时间质谱(UPLC-Q-TOF-MS)方法。样品经混合溶剂甲醇-0.1 mol/L HCl(9:1, v/v)振荡提取,再用MCX固相萃取柱净化处理后,采用UPLC-Q-TOF-MS分析检测。10种化合物在5～100 μg/L范围内均呈良好的线性关系,线性相关系数均大于0.99。本方法的硝西泮、唑吡坦和甲硫哒嗪的定量限(LOQ,以信噪比为10计)为8 μg/kg,三唑仑、艾司唑仑、地西泮、异丙嗪、氯丙嗪和咪达唑仑为10 μg/kg,氯氮平为20 μg/kg。3个添加水平(LOQ、2LOQ、4LOQ)的回收率试验结果表明,10种化合物的回收率在60.6%～108.5%范围内,相对标准偏差均小于10%。本方法可用于动物饲料中违禁精神药物的准确测定。     

Dispersive liquid-liquid microextraction combined with high performance liquid chromatography-fluorescence detection for the determination of carbendazim and thiabendazole in environmental samples

A rapid and sensitive method for the determination of carbendazim (methyl benzimidazole-2-ylcarbamate, MBC) and thiabendazole (TBZ) in water and soil samples was developed by using dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography with fluorescence detection. The water samples were directly used for the DLLME extraction. For soil samples, the target analytes were first extracted by 0.1 mol L⁻¹ HCl. Then, the pH of the extract was adjusted to 7.0 with 2 mol L⁻¹ NaOH before the DLLME extraction. In the DLLME extraction method, chloroform (CHCl₃) was used as extraction solvent and tetrahydrofuran (THF) as dispersive solvent. Under the optimum conditions, the enrichment factors for MBC and TBZ were ranged between 149 and 210, and the extraction recoveries were between 50.8 and 70.9%, respectively. The linearity of the method was obtained in the range of 5-800 ng mL⁻¹ for water sample analysis, and 10-1000 ng g⁻¹ for soil samples, respectively. The correlation coefficients (r) ranged from 0.9987 to 0.9997. The limits of detection were 0.5-1.0 ng mL⁻¹ for water samples, and 1.0-1.6 ng g⁻¹ for soil samples. The relative standard deviations (RSDs) varied from 3.5 to 6.8% (n = 5). The recoveries of the method for MBC and TBZ from water samples at spiking levels of 5 and 20 ng mL⁻¹ were 84.0-94.0% and 86.0-92.5%, respectively. The recoveries for soil samples at spiking levels of 10 and 100 ng g⁻¹ varied between 82.0 and 93.4%.     

有机小分子催化的不对称Strecker反应研究进展

有机小分子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Strecker反应是合成光学活性α-氨基酸衍生物的有效手段. 目前报道的催化不对称Strecker反应的有机催化剂主要有手性胍类、手性(硫)脲衍生物、氮-氧偶极化合物、手性Brønsted酸等, 取得了良好的催化活性和对映选择性. 对各类有机小分子催化剂在有机催化不对称Strecker反应中的应用研究进展, 以及催化剂结构与反应条件对催化活性和不对称诱导作用的影响进行了简要评述.     

超声辐射下硫酸催化合成1,1-二乙酸酯

在超声波辐射和硫酸催化下由芳香醛和乙酸酐反应合成了系列1,1-二乙酸酯衍生物. 以10 mol%硫酸为催化剂, 芳香醛和乙酸酐的物质的量比为1∶1.6, 25～30 ℃下反应10～15 min, 产物产率可达85.2%～98%. 产物结构经1H NMR和IR确证.     

Determination and study on degradation dynamics of fungicide validamycin a residue in soil using pre-column derivatization and capillary gas chromatography

A method for determining validamycin A residue in soil utilizing pre-column derivatization and gas chromatography was developed. Validamycin A was extracted from soil samples by 10% ammonia solution without additional clean-up step and then was derivatized with N,O-bis(trimethylsilyl)acetamide. Derivative of validamycin A was analyzed by gas chromatography on a capillary column. The method showed good linearity in the range of 4.4–142.0 mg/L (r ₂ = 0.9997). The average recoveries were 98.82 and 98.61% with relative standard deviations 1.95 and 2.87% at spiking levels 0.2 and 2.0 mg/kg, respectively. The limit of detection of validamycin A in soil was 0.2 mg/kg. The degradation dynamics of validamycin A in soil was studied. The result shows that validamycin A degradation in soil in the open field in Beijing suburb can be described by the equation c = 6.6109e ^−0.0196t ; the half-life is 35.4 h. The article is published in the original.     

原料奶、婴儿配方奶粉及酸奶中蛋白去除效果的研究

建立了毛细管电泳法分析α-乳白蛋白、β-乳球蛋白A及β-乳球蛋白B的方法,考察了不同浓度冰乙酸(HAc)及三氯乙酸(TCA)对原料奶、婴儿配方奶粉A和B及酸奶中蛋白的去除效果。结果表明,TCA去除蛋白效果优于HAc,不同样品所需TCA浓度不同:2g原料奶需3mL100g/LTCA;0.5g婴儿配方奶粉A和B分别需5mL10g/L及20g/LTCA;2g酸奶则需3mL20g/LTCA才能将蛋白完全沉淀。为原料奶、婴儿配方奶粉及酸奶等乳制品的样品前处理提供了有价值的参考。