连续萃取法研究海湾养殖区沉积物中重金属形态

以连续萃取法研究海湾养殖区沉积物中重金属(Cd, Cu, Pb, Zn)的形态,将重金属分离为酸溶态、还原态、有机质结合态、硫化物结合态和残渣态.分别采用基体匹配法和内标法消除高盐基体对电感耦合等离子体光谱法(ICP-OES)和质谱法(ICP-MS)分析结果的影响.对海洋沉积物标准物质分析结果表明,样品稀释后测定值与标准值一致.比较了本连续萃取法和BCR法对沉积物样品中重金属形态的提取结果,并考察了萃取剂的选择性.实验表明,本方法可用于有机质污染和富营养化环境沉积物中重金属形态分析,特别是有机质结合态和硫化物结合态的分析.     

气相分子吸收法快速测定工业废水中硫化物

建立气相分子吸收法快速测定工业废水中硫化物的方法。水样经乙酸锌溶液固定后转化成硫化锌沉淀，硫化锌沉淀与盐酸反应转化成硫化氢，用载气将硫化氢气体载入气相分子吸收光谱仪的吸光管中，于202.6 nm波长处测定吸光度，吸光度与硫化物质量浓度之间的关系符合朗伯-比尔定律。硫化物质量浓度在0.02～10.0 mg/L范围内与吸光度线性关系良好，相关系数为0.999 6，方法检出限为0.005 mg/L。采用所建方法分别对水质硫化物标准样品、硫化物标准溶液和加标工业废水平行测定6次，测定值的相对标准偏差为1.3%～7.9%。对水质硫化物标准样品和硫化物标准溶液进行测定，测定值与标准值基本一致，相对误差为-5.0%～2.3%。含硫和不含硫工业废水实际样品的加标回收率分别为85.6%和80.1%。该方法快速、灵敏、准确，可用于工业废水中硫化物的检测。     

微波酸溶-电感耦合等离子体质谱测定土壤和沉积物中Be~(2+)

建立了微波酸溶电感耦合等离子体质谱(ICP-MS)测定土壤和沉积物中Be2+的分析方法。采用HNO_3-HCl-HF混酸体系微波消解土壤及沉积物样品,以电热板赶酸的方法对样品进行前处理。优化了仪器参数,采用在线内标法消除基体效应。方法的检出限为0.0029mg/kg。对土壤标准样品进行测定,结果都在标准值范围之内;对土壤及沉积物实际样品进行测定,相对标准偏差均小于5%,加标回收率分别在94.4%~115%和91.5%~113%范围之内。实验结果表明,建立的ICP-MS法与石墨炉原子吸收(GFAA)法对土壤的沉积物中Be~(2+)的测定无差异性。     

亚甲蓝光度法测定废水中硫化物

在环境分析中,硫化物指的是水溶性无机硫化物和酸溶性金属硫化物,包括溶解性的H2S、HS^-、S^2-和存在于悬浮物中的可溶性硫化物以及酸溶性金属硫化物。用亚甲蓝吸光光度法测定废水中硫化物时,由于废水中的还原性物质、带色物和悬浮物对测定有干扰,故测定前需使用适当的预处理方法将硫化物与干扰物质分离,无色透明、不含悬浮物的水样,可采用沉淀分离法进行预处理,     

水蒸气蒸馏返滴定法测定烟草及其制品中总挥发有机酸

烟草中总挥发酸含量与烟草质量密切相关，它对烟草的口味、刺激性和香气都有重要影响，烟草中挥发有机酸测定具有重要意义。总挥发酸的测定一般先在磷酸介质中水蒸气蒸馏分离，然后采用酚酞作指示剂氢氧化钠滴定。传统的水蒸气蒸馏装置蒸馏总挥发酸耗时长，精密度较差；挥发酸多数     

氧化与还原条件下伊通河长春区段沉积物重金属形态特征的对比研究

利用改进的Tessier连续萃取法研究了伊通河长春市自由大桥处不同深度沉积物样品在氧化及还原条件下Cu,Pb,Zn和Ni的形态变化规律,同时分析了沉积物样品中酸可挥发性硫(Acid volatile sulfide,AVS)和同时提取重金属(Simultaneous extract metals,SEM)的含量. 实验结果表明，样品经干燥、研磨处理后,Cu有机/硫化物结合态比例减少40%,锰氧化物结合态的比例显著增加; Pb,Zn和Ni 3种元素有机/硫化物结合态比例均略有下降,变化幅度小于Cu,并重新分配到不同的化学相中. 通过SEM中各金属含量与有机/硫化物结合态中金属含量的对比可知,还原性沉积物中Cu除了与硫化物结合外,很大一部分是以有机物形态存在的,Pb,Zn,Ni,Fe和Mn则主要以硫化物形态存在,各元素形态分析均不同程度地受到萃取剂的影响.     

微波消解ICP-MS测定海洋沉积物中微量元素

采用微波消解-电感耦合等离子体质谱(ICP-MS)法同时测定海洋沉积物中的Cr、Co、Ni、Cu、Zn、Cd、Pb7种微量元素。对微波消解酸体系和微波程序进行了优化,结果表明:由4 mL HNO3与2 mL HF组成的混合酸对沉积物消解效果好;阶段升温,最高温度200℃,消解30 min有着最佳的消解效果。采用本实验方法对7种不同类型的海洋沉积物标准物质进行了测定,测定结果与标准值一致。各元素的检出限在0.009~0.17 ng/g之间。该方法快速简便、准确度高,可用于海洋沉积物样品中多元素同时测定。     

改变相比/顶空气相色谱法测定水中苯的分配常数及其含量

推导了改变气液相比/顶空气相色谱法测定水中苯的分配常数及其含量的基本关系式。采用全挥发技术制备气体标样测定校正因子。通过测定3个不同相比的顶空浓度,计算顶空浓度倒数与相比之间的线性回归方程,测定了23 ℃时苯在纯水中的分配常数为5.878(亨利常数为0.170),与文献值的误差为5.22%。实际测定水样中苯的质量浓度为0.348 mg/L,与配制值0.357 mg/L的相对误差为2.52%。方法检出限可达3.5×10-3 mg/L。     

测定烟草中总挥发酸含量的正交试验研究

利用正交试验设计和单因素实验方法研究了烟草中总挥发酸的测定。结果表明,该项检测的最佳条件为:称取烟样2 g,调节蒸馏液的初始酸度pH3.0,蒸馏9~11 min接收馏出液400~500 mL,设置滴定终点pH 8.4。在此条件下对不同类型的烟叶进行测定,挥发酸含量差异明显。方法的相对标准偏差为2.36%~4.82%,不同烟叶样品的加标回收率为96.5%~107.0%。     

汽油馏分的硫化物形态分布研究

采用气相色谱和硫化学发光检测(GC-SCD)技术,经过对色谱条件的优化,建立了汽油馏分中硫化物形态分布的测定方法。用标准物质的保留时间辅以化学法脱除硫醇、硫醚的方法对107个硫化物进行了定性;标准硫化物保留时间重复测定结果的相对标准偏差(RSD)≤0.25%。用内标法对主要的硫化物和总硫含量进行了定量,方法的加标回收率为96%~115%;同一样品重复测定5次,含硫大于7 mg/kg的硫化物组分重复测定结果的RSD≤8.9%。所建立的方法可用于不同装置的汽油馏分的硫化物形态分布规律的研究。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).