火焰原子吸收光谱法测定铜原尾矿中铅量的研究

铜原尾矿中硅含量较高,针对这一特性,本文提出了试样采用饱和氟化氢铵、盐酸、硝酸溶解,在5%的硝酸介质中,于原子吸收光谱仪上,使用空气—乙炔火焰进行铅的测定,建立了铜原尾矿中铅的测定方法。研究结果表明铅的质量浓度在0.05～3μg/mL范围内与吸光度A有良好的线性关系,方法的相对标准偏差0.92%到2.39%,加标回收率96.0%到106.0%,方法以三倍的空白溶液11次测定值的标准偏差作为检出限,检出限0.08μg/mL。     

火焰原子吸收光谱法测定铜原尾矿中的铅

铜原尾矿中硅含量较高,针对这一特性,提出了试样采用饱和氟化氢铵、盐酸、硝酸溶解,在硝酸(5%)介质中,于原子吸收光谱仪上,使用空气-乙炔火焰进行铅的测定,建立了铜原尾矿中铅的测定方法。研究结果表明铅的质量浓度在0.5~3μg/mL范围内与吸光度A有良好的线性关系,方法的相对标准偏差0.92%~2.4%,加标回收率96.0%~106.0%,方法以3倍的空白溶液11次测定值的标准偏差作为检出限,检出限为0.08μg/mL,方法准确、可靠。     

电感耦合等离子体发射光谱法测定镍铜合金中高含量硅

采用电感耦合等离子体发射光谱（ICP-AES）法对镍铜合金中高含量硅进行了测定.方法对样品的溶解和仪器测量条件以及共存元素干扰进行了系统的研究,选定了仪器的最佳测定条件,硅分析线为251.611 nm,内标元素线为371.029 nm.样品以硝酸为主加盐酸溶解,加氢氟酸控制温度溶解硅,在仪器最佳条件进行测量,并与经典化学法（重量法）结果对照一致.硅元素含量在1%~5%范围回收率为99%~102%,RSD为0.77%.     

电感耦合等离子体原子发射光谱法测定钨钢中硅、锰、磷、铬、镍、铜、钼、钒和钨

采用电感耦合等离子体原子发射光谱法测定钨钢中硅、锰、磷、铬、镍、铜、钼、钒和钨的含量。试样用盐酸、柠檬酸铵、硝酸溶解。基体效应采用基体匹配法消除。硅、锰、磷、铬、镍、铜、钼、钒、钨的分析谱线依次为288.158,257.610,177.495,267.716,213.604,327.396,204.598,310.230,239.709nm。9种元素的质量分数在一定的范围内与其发射强度呈线性关系,方法的检出限(3s)在0.000 3%~0.004 8%之间。方法用于两种标准物质的测定,测定结果与认定值相符,测定值的相对标准偏差(n=5)在0.74%~2.1%之间。方法的回收率在95.0%~107%之间。     

火焰原子吸收光谱法测定铜原矿尾矿中的镉

采用盐酸、氢氟酸、硝酸、高氯酸分步溶解的方式对具有硅、铁含量高等特性的铜原矿尾矿样品进行溶解。在体积分数为5%的盐酸介质中,利用原子吸收光谱法,采用扣除背景方式对样品溶液进行测定。样品溶解较完全,共存元素对镉的测定基本无干扰。方法重现性较好,准确度较高。相对标准偏差在2.3%~8.3%,加标回收率在96.7%~105%,标准样品分析结果与标准值基本一致。能满足日常分析检测的需要。     

ICP-AES法测定镍铬铝钇硅合金中的铝、钇、硅

建立电感耦合等离子体发射光谱测定镍铬铝钇硅合金中铝、钇、硅含量的方法。采用盐酸–硝酸(6∶1)混合酸溶解样品,通过基体匹配消除基体镍的干扰,铝、钇、硅的分析谱线分别为394.401,371.029,251.611 nm。铝、钇、硅的质量浓度分别在1.00～30.00,1.00～20.00,1.00～30.00 mg/L范围内与其发射强度呈良好的线性,线性相关系数均大于0.999,检出限分别为0.013,0.002,0.064 mg/L。加标回收率为94.60%～103.51%,测定结果的相对标准偏差均小于2%(n=11)。该方法快速、稳定,可用于实际生产中镍铬铝钇硅中铝、钇、硅元素的测定。     

容量法快速准确地测定硅铁中硅的要点

硅氟酸钾容量法测定硅铁中硅含量比质量法快速 ,且准确度也能达到要求。因此采用硅氟酸钾容量法较为实用。但由于容量法中溶样、沉淀、洗涤、滴定等过程复杂 ,往往一步控制不严造成试验数据超过允许误差。通过反复试验 ,掌握了以下快速准确测定硅的几个要点 :( 1 )硝酸和氢氟酸分解硅铁时 ,滴加氢氟酸一定要逐滴加入 ,且边滴边摇 ,使反应逐步完成。( 2 )加硝酸钾饱和液使硅氟酸沉淀时 ,一定要控制硅氟酸钾沉淀的酸度为 1 5%～ 2 5% (体积分数 ) ,沉淀温度在 2 5°C以下。夏天 ,在加饱和硝酸钾溶液时 ,应先把塑料烧杯直接放到盛有冷水的盘子…     

多孔硅/硝酸钆复合材料制备与表征

多孔硅/硝酸钆复合材料因具有爆炸能量高和环境危害小等特点而受到世界各国广泛关注.采用电化学阳极氧化法制备新鲜多孔硅并滴加硝酸钆形成复合材料,表征其化学组成与结构.结果表明,当电解液HF与EtOH体积比为1∶1、电流密度为50mA·cm-2、阳极氧化时间为30min时,形成的多孔硅孔隙率较大,适宜与硝酸钆形成复合材料;与新鲜多孔硅相比,滴加硝酸钆乙醇溶液的多孔硅在1675、1534、1382和1217cm-1出现了4个新的吸收峰,结合N1s和Si2p结合能有明显化学位移的现象,表明硝酸钆乙醇溶液与多孔硅之间存在相互作用,结构中有-NH2形成,表面Si-Hx键被氧化为si-O键;当电火花触发时,观察到多孔硅/硝酸钆复合材料爆炸现象.     

复合熔剂熔融-电感耦合等离子体原子发射光谱(ICP-AES)法测定萤石中钾、钠、硅、铁、磷

采用四硼酸锂+偏硼酸锂复合熔剂,高频熔融炉熔融,硝酸浸取方式溶解萤石,用已知含量萤石标准物质制作标准工作曲线,用ICP-AES法联合测定萤石中钾、钠、硅、铁、磷组分含量。选择两条谱线进行分析,方法检出限在0.001～0.22mg/L,样品检测5次的相对标准偏差小于9.3%,测定值与证书值相吻合。     

电感耦合等离子体发射光谱法测定高纯铝中硅

建立电感耦合等离子体发射光谱(ICP-AES)法测定高纯铝中硅元素的分析方法。样品采用碱溶法进行预处理,以氢氧化钠溶液溶解,再加入盐酸、硝酸酸化。选取了硅251.611 nm分析谱线进行分析。硅的质量分数在0.001%~0.01%范围内与光谱强度具有良好的线性关系,线性相关系数为0.9991。该方法检出限为0.00012%,测定结果的相对标准偏差不大于10.2%(n=8),加标回收率为93.2%~104.2%。该方法操作简便,测定结果准确、可靠,适用于快速检测高纯铝中硅元素,具有推广价值。     

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%.     

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.     

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.     

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%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

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.     

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.