高通量研磨-X射线荧光光谱法测定不同植源性食品中硒含量北大核心

为了提高食品的样品检验效率,采用高通量研磨制备样品,利用X射线荧光光谱法对食品中硒含量进行检测。重点研究了样品含水率、样品颗粒粒径、研磨条件、检测条件等因素对检测结果的影响。结果表明:样品干基含水量小于20%,样品颗粒粒径小于100μm;高通量研磨条件为装样量3 g,频率30 Hz,研磨3 min;高精度X射线荧光光谱仪检测条件为检装样量0.2 g,PP膜压紧,检测90 s时的情况下,硒的检出限0.01 mg/kg,仪器的精密度小于5%,与粉碎法进行对比,相对偏差在-10.37%~8.05%。说明高通量研磨-X射线荧光光谱法检测食品中硒含量的方法快速、准确,可以满足批量样品现场检测分析需求。     

高频红外碳硫仪测定地球化学样品中有机碳

利用高频红外碳硫仪，建立盐酸预处理-红外吸收法测定地球化学样品中有机碳含量的分析方法。对样品的称取量、助熔剂的添加量、盐酸溶液的体积分数等条件进行了优化。高频红外碳硫分析仪专用陶瓷坩埚经过1 200℃高温处理后，能够有效降低空白值。优化后的分析条件为：确定称样量为50 mg，使用体积分数为40%的盐酸溶液，选择0.5 g纯铁屑和1.5 g钨粒作为助熔剂；对土壤和水系沉积物等不同类型的地球化学样品进行6次测定，选择国家一级标准物质作为实验对象，其检测结果的相对误差为0.23%～3.63%，相对标准偏差为0.592%～4.551%，符合《多目标区域地球化学调查规范》规定，满足分析测试要求。该方法测定结果准确、稳定，流程短、操作简单，适用于地球化学样品中有机碳含量的测定。     

高频燃烧红外吸收法测定铅精矿中的硫

利用高频燃烧红外吸收碳硫仪测定铅精矿中的硫含量。低硫含量(S<5%)铅精矿样品直接称样测定;高硫含量(S>5%)铅精矿样品添加稀释剂后称样测定。对样品称样量、助熔剂类型及用量等条件进行了研究,获得最佳分析条件。通过空白实验测得方法检出限为0.0010%,利用铅精矿有证标准物质进行精密度和准确度验证,方法的标准偏差在0.295%~1.3%之间,结果表明该方法精密度高、准确度好,能够满足铅精矿中硫含量的快速准确测定。     

全自动汞分析系统在土壤总汞测定中的应用

应用Hydra C全自动汞分析系统对土壤中总汞量的测定进行了研究。土壤样品经研磨并通过孔径0.15mm筛。称取一定量的样品(0.1g)置于样舟中,直接由氧气(载气)自动送入仪器的热解炉中,经干燥(300℃),热解(800℃)和催化还原(600℃)后进入金汞齐化器选择性吸收汞。然后加热汞齐释出汞蒸气,通过吸收池,用原子吸收光谱法在波长253.65nm处测得其吸收值。采用土壤标准物质由仪器自动制备汞含量在30.0ng以内以及30.0~300.0ng范围内的高、低浓度两条标准曲线。用2个含汞样品进行分析,得到测定结果的相对标准偏差(n=6)均小于2.0%。在无样品及称有0.1g样品条件下,分别进行10次测定,测得仪器和方法的检出限(3s)依次为0.022,0.082ng。对7件土壤样品分别用本法与原子荧光光谱法测定其汞量,经t检验法检验,表明两组数据间无显著差异。     

高频红外碳硫仪测定土壤、水系沉积物和矿石中的硫

应用高频红外碳硫分析仪对土壤、水系沉积物、镍矿石及铅锌矿石样品中的硫含量进行测定.通过优化样品称样质量和助熔剂添加量,建立了适合分析不同样品中硫含量的最佳方法:氧气流量为2.8 L/min,土壤和水系沉积物等低硫含量样品称样质量为0.050 g,镍矿石和铅锌矿石等高硫含量样品称样质量为0.030 g,纯铁助熔剂添加质量...     

高频燃烧-红外分析仪测定海洋沉积物的总碳含量

应用高频红外分析仪测定海洋沉积物的总碳含量。于坩埚中预置纯铁屑0.2g,准确称取沉积物样品50.0 mg置于坩埚中,再加入纯铁屑0.2g,使其与样品充分混匀,再加入钨粒1.6g,使其均匀覆盖在样品上面。加入的铁屑与钨粒起了助熔剂的作用。以下按仪器工作条件进行通氧燃烧和测定。按所提出的分析条件测定了两种标准物质(GBW 07364和GBW 07366)中的总碳量,测定结果与认定值相符,测定值的相对标准偏差(n=10)分别为2.3%,1.8%。该方法的检出限(3s)为0.000 4%。应用此方法测定了18种海洋沉积物样品中的总碳量,并用元素分析仪对这些样品进行了校对试验,结果表明两方法的测定结果基本相符。     

改性污泥与无烟煤成浆性的研究

采用阴离子表面活性剂萘磺酸钠甲醛缩合物、聚羧酸钠作为分散剂,考察了不同污泥用量时污泥煤浆的成浆性能。结果表明,当污泥(干基)添加量为煤质量的4%时,成浆浓度超过60%,随着污泥用量的提高,污泥煤浆的成浆浓度降低。污泥加入后,浆体的稳定性增强,污泥比例越高,产生沉淀的时间延长。当污泥(干基)添加量为煤质量的4%时,产生沉淀的时间超过160h,与使用稳定剂效果相当。使用不同添加剂制备的污泥煤浆均呈假塑性。污泥疏松的絮状结构,蜂窝状的外表面,强大的吸水性是造成污泥煤浆成浆浓度下降,稳定性增加的主要原因。     

污泥/钛铁矿复合吸附剂的制备及其吸附Cr(Ⅵ)研究

以城市污水处理厂剩余污泥为原料,添加微量钛铁矿,采用氯化锌活化法制备复合吸附剂,并考察了其对含Cr(Ⅵ)废水的处理效果。研究表明:钛铁矿添加量1.5%、氯化锌浓度3 mol/L、固液比1∶2、活化温度550℃和活化时间40 min时,复合吸附剂碘吸附值可达523.24mg/g,比表面积为285.003 m2/g,相对于不添加钛铁矿的纯污泥吸附剂分别提高了27.95%和43.08%;吸附Cr(Ⅵ)废水研究表明,当pH为1.5、吸附剂用量为4 g/L、吸附时间为120 min时,吸附率可达99.17%,吸附量为12.4 mg/g。     

氧弹燃烧法测定固体的分解焓

以碳酸钡分解焓测定为例,探讨了用氧弹热量计测定固体分解焓的方法,建立了固体分解焓氧弹法测定技术。准确称取一定量的测试样品和基准物质,均匀混合后压片,放入氧弹中充入高压纯氧,然后将测试样品在氧弹中完全灰化,并记录燃烧前后时间与量热计温度变化数据,将测试数据用自编的氧弹燃烧法数据处理系统进行分析。结果表明,用氧弹燃烧法测定固体的分解焓是可行和可靠的,对进一步拓展用氧弹法测定煤炭、污泥、饲料、建筑材料等材质的热值具有参考价值。     

氢化物发生-原子荧光光谱法测定木薯干及其发酵产物酒精中铅量

提出了用氢化物发生-原子荧光光谱法测定木薯干及其发酵产物(主要指用木薯干发酵所产生的酒精)中铅量的方法。其中木薯干样品系用硝酸-高氯酸(4+1)的混合酸在微波消解仪中作消解处理,将所得溶液蒸发至近干后,用盐酸(1+19)溶液溶解残渣。先后加入铁氰化钾溶液及草酸溶液分别消除铜(Ⅱ)及铁(Ⅲ)、钼(Ⅵ)、镍(Ⅱ)所引起的干扰。然后按所优选的条件用氢化物发生-原子荧光光谱法测定溶液中铅(Ⅱ)量。测得铅(Ⅱ)的质量浓度在1~280μg.L-1范围内与相应的峰面积测量值之间呈线性关系,其检出限(3S/N)为5μg.L-1(对木薯干样品)及1μg.L-1(对酒精样品)。以木薯干和酒精为基体添加标准溶液,木薯干和酒精的平均加标回收率分别为97.9%和93.8%,测定结果的相对标准偏差(n=8)依次为2.68%及2.14%。     

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

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.