高频红外碳硫分析仪测定石膏矿中的三氧化硫

利用高频红外碳硫仪对石膏矿中三氧化硫含量的测定进行了研究,取得了较好的结果.方法检出限为0.003 0%.用石膏标准样品(GBW03109a,GBW03110)进行分析,测定值与认定值相符,测定值的相对标准偏差(n=9)在0.32%~0.81%之间.使用石膏标准样品(GBW03111)进行本法与国标硫酸钡重量法做比对试验,测定结果无显著性差异.加标回收率为96.4%~104.0%.     

电感耦合等离子体质谱法测定重晶石中的微量元素

重晶石样品(0.200 0~0.250 0g)经氢氟酸(6mL)、盐酸(3mL)和硝酸(1mL)溶样,蒸干,最后用盐酸(1+3)溶液4mL溶解残渣,加水定容至100mL。采用电感耦合等离子体质谱法测定其中锶、铝、钙、镁、钾、钠、铜、铅、锌等9种微量元素的含量。用一级标准物质(GBW07811、GBW 07814、GWB 07812)绘制标准曲线,以铼为内标物。方法的检出限在2.2×10-7~1.51×10-6之间。方法用于实样分析,测定值的相对标准偏差(n=10)在2.2%~3.8%之间。应用此方法分析了4种重晶石标准物质(GBW 07813、GBW 07815、GBW 07816、GBW 07817),所得测定值与认定值相符。用标准加入法做方法的回收试验,测得回收率在90.0%~120%之间。     

石墨炉原子吸收光谱法测定矿石中铂、钯、铑、铱

矿石样品铂、钯、铑和铱经铅试金富集,所得金属合粒用硝酸-盐酸溶解,用石墨炉原子吸收光谱法测定矿石样品中铂、钯、铑和铱的含量。在优化的石墨炉工作条件下测得:铂的质量浓度在20～150μg.L-1、钯在15～120μg.L-1、铑和铱在6～100μg.L-1范围内与其吸光度呈线性关系,检出限(3s/k)依次为4.6,4.0,1.5,1.5μg.L-1。方法用于分析了2种矿石国家标准物质(GBW 07341、GBW 07342),测定结果与认定值相符。方法的回收率在87.6%～105.5%之间。测定值的日内和日间相对标准偏差(n=7)分别在2.8%～3.6%和3.5%～4.7%之间。     

基于五元助熔剂的高频-红外吸收法测定硅铁中碳、硫含量

以EMIA-820V型高频-红外碳硫分析仪为测量仪器,采用W,Sn,Fe,M o和Ni混合的五元助熔剂法对硅铁中C,S的含量进行了测定。通过对分析电流、称样量、助熔剂配比等条件实验的优化,确定了最佳分析条件为:分析电流175 m A,称样量0.106~0.156g,助熔剂配比W 1.2 g+Sn 0.5 g+Fe 0.5 g+M o 0.045 g+Ni 0.05 g。结果熔样后坩埚光滑无飞溅,数据精密度RSD7.0%,测定范围为C:0.0030%~0.025%,S:0.0030%~0.025%。本方法相比国标方法实现了碳、硫同时测定,扩大了碳、硫测定的含量范围。本法可满足硅铁合金中碳、硫量的日常分析,且为硅铁合金中碳、硫量分析的国家标准修订提供依据,为多元助熔剂法的应用提供参考。     

电感耦合等离子体质谱法测定工业纯铁中13种元素

工业纯铁样品用盐酸、硝酸、氢氟酸微波消解,消解液用水定容至100.0mL,采用电感耦合等离子体质谱法测定上述溶液中硼、镁、钙、钛、铬、镍、铜、锆、铌、锡、锑、铅、铋等13种元素的含量。采用内标法定量,13种元素的线性范围均为0.000 10%~0.015 00%,检出限(3s)为0.24~0.66μg·L^-1。用标准加入法做方法的回收试验,测得回收率为84.0%~106%。方法应用于纯铁标准样品(GBW 01401b、GBW 01402g、SRM 2167、YSBC 11247-2007)的分析,测定值与认定值相符,测定值的相对标准偏差(n=6)为0.80%~9.6%。     

管式炉直接燃烧-红外吸收光谱法同时测定硅铁中碳和硫量

提出了管式炉直接燃烧-红外吸收光谱法测定硅铁中碳、硫含量的方法。对试验条件进行了优化,选择氧化铜(1.5g)为助熔剂,样品称样量为0.2～0.3g,碳和硫的分析时间为60s。方法的检出限为硫0.001%,碳0.004%。分析了标准样品(BH1917-1)进行准确度及精密度试验,测定结果与认定值相符,碳和硫测定值的相对标准偏差(n=10)分别小于4%和8%。     

石墨炉原子吸收光谱法测定土壤中的银

建立石墨炉原子吸收光谱法测定土壤中的银。样品经王水溶液(1+1)水浴溶解,用体积分数为10%的盐酸溶液定容于50 mL比色管中,以7%硫脲为基体改进剂,采用石墨炉原子吸收光谱法与校准曲线测定同批样品溶液的吸光度,从校准曲线查得样品溶液中的银量。在优化的实验条件下,校准曲线方程为y=–0.139 66x~2+0.532 03x+0.0013,相关系数为0.9999,方法检出限为0.006μg/g。用该方法测定国家标准物质GBW07448,GBW 07456,GBW 07306,GBW 07312,测定值与推荐值基本一致,相对误差为–0.4%～2.3%,测定结果的相对标准偏差为1.01%～3.67%(n=6)。该方法操作简便、快捷,满足水系沉积物及土壤中银测定的质量要求,适合批量检测。     

高频燃烧–红外吸收法测定石墨及其制品中的硫含量

建立高频燃烧–红外吸收法测定石墨及其制品中的硫含量。结合高频红外碳硫分析仪器特点,试验确定了方法的实验条件:试样粉碎至2.5 mm以下颗粒状,所有试样均为干燥状态,称样量控制在0.200 0~0.300 0 g之间,助熔剂为纯铁和钨粒,助熔剂添加顺序为纯铁+样品+钨粒。采用该方法对石墨标准样品进行测定,测定结果与标准值相符合,测定结果的相对标准偏差为0.86%~1.96%(n=10)。该法可用于石墨及其制品中硫含量的测定。     

沉淀分离-密闭消解-电感耦合等离子体质谱法测定铬铁矿中铂族元素EI北大核心CSCD

建立了沉淀分离-密闭消解-电感耦合等离子体质谱法测定铬铁矿中铂族元素的新方法。采用硫磷混酸溶样(1:2,V/V),以硫酸肼为还原剂,实现了硫脲对包括Os在内的全部铂族元素的沉淀富集,沉淀经密闭溶样技术快速消解后接ICP-MS测定。试验中筛选出HBr来消除Os的记忆效应,并考察了Os在王水介质中的稳定性。结果表明:铂族6个元素的线性相关系数均在0.999以上,对标准物质GBW07292平行测定6次的相对标准偏差(RSD,n=6)在2.7%~8.4%之间,方法检出限(3σ)在0.055~0.21ng/g,采用国家一级标准物质GBW07201,GBW07202,GBW07292进行方法验证,测定值与认定值基本一致。     

电感耦合等离子体质谱法测定铅锌矿区土壤中微量元素

铅锌矿区土壤样品经高压密闭消解罐消解处理,采用电感耦合等离子体质谱法测定其中铬、砷、镉、镍、铜、锰、锌、钴和铅等9种微量元素的含量。通过加入盐酸降低硫对铜测定的干扰,运用干扰方程校正光谱干扰,用内标校正消除基体影响。砷的检出限(3s)为1×10-4mg·g-1,其余8种元素的检出限(3s)均为1×10-5mg·g-1。9种元素的回收率在90.1%~109.1%之间。方法用于土壤标准物质(GBW 07401、GBW 07404、GBW 07406)分析,测试结果与标准值相吻合。     

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.     

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.     

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.     

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.     

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.     

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.     

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.