X射线荧光光谱法测定钒铁合金中主次元素含量

用熔融制样法将钒铁合金样品在铂金坩埚中与四硼酸锂和偏硼酸锂熔融,熔体在铂金坩埚中自动成型,用X射线荧光光谱法测定钒铁合金中钒、硅、锰、铝和磷等主次元素含量。经试验求得熔融时,四硼酸锂、混合溶剂(四硼酸锂∶偏硼酸锂=67∶33)和样品的最佳质量比为30比5比1。各元素的检出限在12.4～51.2μg.g-1之间。方法用于标准样品分析,测定值与认定值相符。     

X射线荧光光谱(XRF)法测定绿泥石中镁、铝、硅、磷、钾、钙、钛、铁元素含量

建立了X射线荧光光谱法测定绿泥石中镁、铝、硅、磷、钾、钙、钛、铁元素含量的快速分析方法。以标准物质及标准物质与基准试剂氧化镁、氧化钙人工混合配制标样的方法建立标准工作曲线,重点讨论了熔剂和脱模剂的选取。最佳熔样条件：采用8.0g四硼酸锂和偏硼酸锂混合熔剂(质量比67: 33)+0.8g样品并添加溴化锂作为脱模剂,熔样温度1100℃,熔样时间10min。该方法相对标准偏差(n=12)均小于5.57%,绿泥石样品测定结果与化学法一致,硅酸盐标准物质测定结果均满足不确定度要求。     

X射线荧光光谱法测定钒钛磁铁矿中的主次量元素

采用X射线荧光光谱法测定钒钛磁铁矿中铁、钛、硅、铝、锰、钒、钙、镁等8种主次量元素。样品以四硼酸锂、偏硼酸锂和氟化锂(质量比为4.5比1比0.4)为熔剂,脱模所得熔块用于X射线荧光光谱分析。以GBW 07224、GBW 07225、GBW 07227、YSBC 19701-76、GSB 03-2584-2010、YSBC 19722-2011等6种标准物质和光谱纯二氧化硅、氧化钙、氧化铝、五氧化二钒、二氧化钛为基础制作校准曲线。优化了各元素的基体校正数学模型。各元素的检出限在3.79~39.06mg·kg-1之间。对钒钛磁铁矿标准样品GBW 07225重复测定10次,测得其相对标准偏差(n=10)在0.83%~2.9%之间。方法用于钒钛磁铁矿标准样品GBW 07225,GBW 07227的分析,所得结果与认定值相符。     

X射线荧光光谱法测定高铬型钒渣中主次组分北大核心CSCD

称取于750~800℃灼烧2h后的试样0.300 0g,置于盛有4.000 0g四硼酸锂、3.000 0g偏硼酸锂、0.500 0g碳酸锂的铂黄坩埚中,搅匀,加入300g·L-1溴化锂溶液0.5mL,在(1 050±20)℃熔融制片,采用X射线荧光光谱法测定高铬型钒渣中主次组分含量。采用钒渣标准样品和由标准样品加基准物质配制成的系列校准样品绘制校准曲线以消除基体效应,选择分析谱线并进行谱线重叠干扰校正。各组分的质量分数在一定范围内与荧光强度呈线性关系。方法用于分析高铬型钒渣样品,所得结果与滴定法、电感耦合等离子体原子发射光谱法的结果一致,测定值的相对标准偏差(n=10)在0.030%~7.3%之间。     

X射线荧光光谱法测定高铬型钒渣中主次组分

称取于750~800℃灼烧2h后的试样0.300 0g,置于盛有4.000 0g四硼酸锂、3.000 0g偏硼酸锂、0.500 0g碳酸锂的铂黄坩埚中,搅匀,加入300g·L-1溴化锂溶液0.5mL,在(1 050±20)℃熔融制片,采用X射线荧光光谱法测定高铬型钒渣中主次组分含量。采用钒渣标准样品和由标准样品加基准物质配制成的系列校准样品绘制校准曲线以消除基体效应,选择分析谱线并进行谱线重叠干扰校正。各组分的质量分数在一定范围内与荧光强度呈线性关系。方法用于分析高铬型钒渣样品,所得结果与滴定法、电感耦合等离子体原子发射光谱法的结果一致,测定值的相对标准偏差(n=10)在0.030%~7.3%之间。     

熔融制样-X射线荧光光谱法测定工业硅中总硅、二氧化硅和其他杂质组分

将四硼酸锂内衬坩埚熔融制样方法应用于X射线荧光光谱法测定工业硅中总硅、二氧化硅和其他杂质组分(铝、铁、钙、镁、钛)。在熔融制样前,样品(1.000 0g)经直接灼烧(700～750℃)计算灼减量并除去样品中碳。称取上述灼烧后的样品0.200 0g,与碳酸锂1.700g和600g·L~(-1)硝酸铵溶液0.1～0.3mL混匀后移入四硼酸锂内衬坩埚中,于710～720℃预氧化10～12min。将此经预氧化的混合物及其内衬坩埚一起转移至预置有3.000g硼酸的铂金坩埚中,加入400g·L~(-1)溴化铵溶液0.1～0.4mL,于熔样机中静置熔融8min,摇动熔融12min,冷却,脱模后即得样品的玻璃片。选取测定元素的氧化物,按0.200 0g称样量模拟制备了5个校准样片,各组分的质量分数在一定范围内与其对应的X射线荧光强度呈线性关系,提出了样品中二氧化硅含量的计算公式。方法用于5个工业硅样品的分析,测定结果与湿法分析测定值相符。     

熔融制样-X射线荧光光谱法测定直接还原铁中主次元素含量

应用熔融制样-X射线荧光光谱法测定了直接还原铁中主次元素的含量。样品置于铂金坩埚中,以四硼酸锂和偏硼酸锂为熔剂于1 050℃熔融20min,将熔化的样品倒入铂金模具中,所制得的片样用于X射线荧光光谱分析。以铁矿石标准物质GBW 07221等25种标准物质制作校准曲线,以固定理论α影响系数法校正基体效应。方法用于实际样品的分析,所得结果与其他方法测定值相符。测定值的相对标准偏差(n=10)在0.31%~16%之间。     

熔融法制样-X射线荧光光谱法测定锌精矿中主、次组分含量

应用X射线荧光光谱法测定了锌精矿中主次量组分(包括锌、硫、铁、硅、铅、铜、砷、银、镉、锡及锑)。锌精矿样品(0.6g)与6.3g四硼酸锂和3.2g硝酸锂置于铂-金坩埚中拌匀,先在500℃随即升至700℃灼烧10min,使样品中的硫离子预氧化为硫酸盐。硝酸锂与四硼酸锂生成四硼酸锂和偏硼酸锂混合物熔剂,在1 030℃熔融样品10min,将熔化的样品倒入样模中,冷却后脱模所得熔块用于X射线荧光光谱分析。对在预氧化及熔融过程中由于样品组成变化及质量的增加所造成的基体干扰,采用基于Sherman方程的可变理论α影响系数法进行校正。在所测定的元素中,锌和硫的校准曲线范围依次为27%～62%和10%～35%,两者的标准偏差均小于0.2%。应用所提出的方法分析了2个CRM(GBW 07168和SRM 113b),所得测定值与认定值一致。     

X射线荧光光谱法分析镁砂中的主次成分

采用镁砂标准样品作为校准样品,建立了熔融制样X射线荧光光谱法测定镁砂中MgO,Al2O3,SiO2,CaO,P2O5,Fe2O3的方法。采用熔融法为样品片和校准片的制备方法,选择四硼酸锂-偏硼酸锂(67+33)为助熔剂,1.00mL LiBr溶液为脱模剂,熔融温度为1 100℃,熔融时间20min。对镁砂样品测定的相对标准偏差(RSD)小于3%,对不同镁砂标准样品进行测定,方法的测定结果与认证值相吻合。     

X射线荧光光谱法测定煤灰成分的改进

样品以四硼酸锂和偏硼酸锂为熔剂,硝酸铵为氧化剂,溴化锂为脱模剂,采用玻璃状熔片法制样。选用标准样品及其标准样品间相混合配制的混合样品制作工作曲线,并以α系数和经验系数法校正元素谱线干扰和基体效应,用X射线荧光光谱法对煤灰中的二氧化硅、氧化铝、氧化铁、氧化钙、氧化镁、五氧化二磷、氧化钾、氧化钠、氧化钛、五氧化二钒、氧化锰和三氧化硫等12种主次组分进行测定。方法分析结果与化学法和电感耦合等离子体原子发射光谱法测定值相符;对同一样品按所建方法分别熔融制备10个熔片进行测定,各组分测定值的相对标准偏差(n=10)在0.06%～2.4%之间。     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.