微波等离子体发射光谱法同时测定特色南药中多种元素

特色南药样品利用硝酸微波消解后,在优化的还原剂浓度下,采用多模式样品导入系统和微波等离子体原子发射光谱法(MP-AES)对样品溶液中Al,As,Hg,Ca,Cu,Cr,Pb,Zn等17种元素进行同时分析,考察了其在特色南药材中的含量。结果表明,MP-AES对目标元素有较好的检出限,2种标准物质的分析结果与ICP-MS分析结果及标准值一致,其中可蒸气发生元素(As,Hg,Sb和Se等)未检出。方法对金属元素的检出限为0.05~0.53μg/g,对于氢化物可蒸气发生元素和Fe的检出限为0.93~5.40μg/g。通过该方法进行测定,发现南药样品中Cd和Cu含量低于中国药典的限值,而Cr和Pb含量明显高于欧洲草药材的限值,As和Hg需优化方法降低检出限后方可用于样品质量控制。本方法检出限较低,线性范围较宽,分析结果准确、快速,可进行多元素同时分析,能满足对南药材中多种元素的分析要求。     

微波消解-电感耦合等离子体质谱(ICP-MS)法同时测定畜禽粪便中7种重金属元素

粪便样品干燥、研磨后,称取0.25 g样品,加入8 mL硝酸,采用微波消解方法进行前处理.采用KED模式消除质谱干扰,采用内标校正消除非质谱干扰(Ge作为Cu、Zn、Cr的内标,Bi作为Hg和Pb的内标,Rh作为As和Cd的内标),建立了可同时测定畜禽粪便中Cu、Zn、Cr、As、Cd、Pb、Hg 7种重金属元素的微波...     

ICP-MS测定紫菜中的总砷

采用电感耦合等离子体质谱(ICP-MS)法,对紫菜中的微量元素砷进行了测定。用HNO3-H2O2混合体系分解样品,通过在线加入内标元素校正基体效应和接口效应,通过EPA 200.8干扰校正方程校正质量数干扰。校正曲线的相关系数大于0.999 9,As的检出限(3σ)为0.021μg.L-1,样品分析结果的相对标准偏差3.7%(n=6),加标平均回收率为96.0%。通过测定贻贝标准物质GBW 08571验证了该方法的准确性。     

高压微波消解-电感耦合等离子体质谱(ICP-MS)法测定小米样品中铜铅锌镉铬镍砷

准确测定小米中的重金属对控制和提高食品安全具有非常重要的意义。采用高压微波消解法,以HNO₃-H₂O₂体系处理样品,选择⁵²Cr、⁶⁰Ni、⁶³Cu、⁶⁶Zn、⁷⁵As、¹¹¹Cd、²⁰⁸Pb为测量同位素,采用He气模式的碰撞反应池技术测定Cr和As,采用仪器自带干扰校正公式对Cd的测定结果进行校正,建立了电感耦合等离子体质谱(ICP-MS)法测定小米样品中Cu、Pb、Zn、Cd、Cr、Ni、As的方法。重点对溶样条件进行了优化,结果表明在优化的实验条件下,校准曲线的相关系数均不小于0.999,检出限为0.000 5～0.01μg/g,测定下限为0.002～0.4μg/g。按照实验方法对小米成分分析标准物质中Cu、Pb、Zn、Cd、Cr、Ni、As平行测定12次,各元素测定值与认定值基本一致,相对标准偏差(RSD)均在7.0%以内。采用实验方法对蔚县小米样品进行分析,结...     

等离子体质谱-氧气碰撞池技术测定复杂基体样品中痕量砷和硒

本实验采用氧气碰撞/反应池技术促使分析物生成氧化物离子,避开原来的双电荷离子干扰.同时采用负的动能歧视效应来改善氧化物离子的通过率,对在新的谱线位置上出现同量异位素干扰辅以数学校正方法.实验发现, 有机试剂的增敏效应同样适合于As和Se的氧化物离子,1%甲醇溶液用于改善As和Se的分析灵敏度.在解决这类样品中微量As和Se的分析难题上,本方法显示了很好的效果,检出限为:As 0.0045μg/L, Se 0.0062μg/L,背景等效浓度:As 0.022μg/L,Se 0.025μg/L,分析结果的误差在标准物质的允许误差范围内,极大改善了实际样品分析结果的准确度.     

铑靶康普顿散射校正XRF测定铝用碳素材料中的微量元素

通过对常用粘结剂中杂质元素含量的测定,选择硬脂酸做粘结剂,研磨压片制备样品,用X射线荧光光谱仪(XRF)测定铝用炭素阳极材料中硫、钒、钠、钙、硅、铁、镍、钛、铝、镁、磷、铅、锌、铬、锰含量的元素含量。通过实验确定了最佳的样品和粘结剂比例为12 g炭素试样加入2 g硬脂酸,研磨时间为20 s。测定铅元素时,选择一点法扣除背景,通过谱线强度数据确定使用PbLβ1做分析线。用铝用炭素阳极材料系列标准样品制作校准曲线,用铑靶康普顿散射内标校正铁、镍、铅、锌、铬、锰等元素,其余元素用经验系数法校正。样品精密度试验表明,样品中各元素测定结果的相对标准偏差(RSD,n=11)一般在8%以下,最高的钠元素和钛元素也在10%左右,未知样品的检测结果与标准结果没有显著性差异。     

高效液相色谱-电感耦合等离子体质谱测定蟾酥中铜、砷、镉、汞、铅含量及砷化学形态

建立了微波消解-电感耦合等离子体质谱(ICP-MS)测定蟾酥中Cu、As、Cd、Hg、Pb等元素含量的分析方法,检出限为0.28～5.7 μg/L,元素加标回收率均在91.5%～115%.用1.2 mol/L HCl浸提蟾酥中的As形态,利用高效液相色谱(HPLC)与电感耦合等离子体质谱(ICP-MS)联用技术对蟾酥样品中的As化学形态进行了初步探讨,发现其中As主要以有毒的无机As(Ⅴ)形态存在,并讨论了形态分析的方法及结果.本方法适用于蟾酥中药样品质量控制和安全评估的要求.     

电感耦合等离子体质谱法测定垃圾焚烧飞灰中重金属的研究

基于全自动消解仪优化程序,以HNO3-HF-HClO4消解体系消解飞灰样品,通过选择合适的待测同位素以及干扰元素校正方程校正质谱干扰,建立了全自动消解-电感耦合等离子质谱法（ICP-MS）测定飞灰样品中铍、钒、铬、锰、镍、铜、锌、镉、铅等9种元素的新方法。该方法采用嵌片技术和碰撞模式消除基体干扰,采用单一内标103Rh进行信号漂移校正,9种元素校准曲线的线性相关系数均大于0.999,方法检出限在0.01~0.3 μg/g之间。该方法用飞灰标准物质SRM1633C进行验证,平均RSD在0.54%~2.38%之间,加标回收率为85%~120%,各元素的测定值与标准值吻合。该分析方法具有较好的准确度和精密度,适合垃圾焚烧产生飞灰样品中全量金属的测定。     

微波消解-电感耦合等离体子质谱法(ICP-MS)同时测定畜禽粪便中7种重金属元素

粪便样品干燥、研磨后,称取0.25 g样品,加入8 mL硝酸,采用微波消解方法进行前处理。采用KED模式消除质谱干扰,采用内标校正消除非质谱干扰(Ge作为Cu、Zn、Cr的内标,Bi作为Hg和Pb的内标,Rh作为As和Cd的内标),建立了可同时测定畜禽粪便中Cu、Zn、Cr、As、Cd、Pb、Hg 7种重金属元素的微波消解-电感耦合等离子体质谱法。方法线性相关系数均在0.9995以上,检出限为0.005~0.305μg/L,加标回收率为83.6%~112%,相对标准偏差为0.70%~5.6%。方法灵敏度、准确度和精密度高,实用性强,适用于同时检测畜禽粪便中多种重金属元素,对畜禽粪便的科学还田具有指导意义。     

X射线荧光光谱法测定土壤和水系沉积物等样品中碳、氮、氟、氯、硫、溴等42种主次和痕量元素

采用粉末压片制样,用X射线荧光光谱法测定土壤、水系沉积物等样品中C、N、F、S、Cl、Br、Na、Mg、Al、Si、P、K、Ca、Ti、Mn、Fe、Co、Ni、Cu、Zn、Pb、Ga、As、Rb、Sr、Y、Zr、Nb、Th、U、Ba、La、Ce、Nd、Ge、Yb、W、Hf、Sc、Sn、Mo、Cs等42种元素。着重研究了C、N、F、S和Cl等元素的测量条件和存在问题;并研究了痕量元素的背景选择和谱线重叠校正的问题。方法的检出限,精密度和准确度绝大多数能满足覆盖区多目标地球化学调查样品的质量要求。     

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.     

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%).     

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.     

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.     

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.     

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.