流动注射氢化物发生-原子吸收光谱法测定食品中的无机砷

探讨并建立了流动注射氢化物发生-原子吸收光谱(FI-HAAS)法测定食品中无机砷的样品前处理方法.该法简便快捷,用6种国家标准参考样品进行考察,分析结果可靠.     

氢化物发生-原子吸收光谱法测定食盐中微量铅

食盐中铅测定采用萃取-原子吸收光谱法，方法使用有机试剂，操作也复杂。采用石墨炉原子吸收光谱法直接测定，氯化钠干扰很大。本文提出氢化物发生-原子吸收光谱法测定食盐中铅。采用WHG-102A2型流动注射氢化物发生器与原子吸收光谱仪配合，载气压力作为自动化能源，流动注射方     

流动注射氢化物发生-原子吸收光谱法测定中药中的微量砷

探讨了流动注射氧化物发生-原子吸收光谱法测定微量砷的最佳条件,建立了中药中微量砷的流动注射氧化物发生-原子吸收光谱分析方法。砷的检出限为0.59μg/L,线性范围为0～30μg/L,线性回归方程为A=0.02228c 6.282×10~(-3),相关系数r=0.9992,相对标准偏差为2.6％～4.4％,回收率为91％～103％。方法操作简便、快速,灵敏度及自动化程度高。     

流动注射-氢化物发生-原子吸收光谱法测定中草药中砷

中草药样品经硝酸-高氯酸-硫酸消化处理后,在酸性条件下用硫脲和抗坏血酸将砷(Ⅴ)还原为砷(Ⅲ),然后再以硼氢化钾为还原剂,稀盐酸为载液,用流动注射氢化物发生原子吸收光谱法测定砷含量.砷的质量浓度在1.6～32.0 μg·L-1范围内与其吸光度呈线性关系,检出限(3s/k)为0.32 μg·L-1.用此方法分析了3种草药样品,砷的测定值的相对标准偏差(n=6)在5.1%～8.1%之间,加标回收率在91.4%～106.1%之间.     

流动注射-氢化物发生-原子吸收光谱法测定香烟接装纸中的痕量铅

研究了流动注射-氢化物发生-原子吸收光谱法测定香烟接装纸中铅含量的分析方法.讨论了氢化物发生的最佳条件,方法的回收率为95%～104.5%,检出限可达0.22 ng/mL,线性范围在0～50 ng/mL,线性回归方程为y=0.012x 0.0106,相关系数γ=0.9997,相对标准偏差在1.2%～3.3%.     

氢化物发生-原子吸收光谱法测定食品中铅、镉、汞

提出了一种顺序流动注射-氢化物发生-原子吸收光谱分析方法。食品样品经硝酸-高氯酸（4＋1）混合酸消化,以硼氢化钾为还原剂,盐酸溶液为载流,用氢化物发生-原子吸收光谱法测定食品中铅、镉和汞含量的方法。在优化的试验条件下,铅、镉和汞的质量浓度分别在一定的范围内与其吸光度呈线性关系,检出限（3s/k）分别为0.20,0.04...     

中成药中微量汞的流动注射-冷原子吸收测定方法研究

研究了流动注射氢化物发生-原子吸收光谱法测定微量汞时的最佳条件,建立了中成药中微量汞的流动注射.冷原子吸收光谱分析方法。测定中成药中汞的检出限为2.7×10-9,线性范围0-60μg·L-1,相对标准偏差小于5％,加标回收率为95％-98％。方法操作简便、快速、灵敏、自动化程度高,应用于实际中成药样品中微量汞的测定,结果满意。     

氢化物发生-原子吸收光谱法测定粗铜中砷、锑、铋

氢化物发生-原子吸收光谱法具有分析速度快、灵敏度高、准确度高、分离效率高、设备简单、运行成本低等特点,已广泛应用于工业、农业、医药、卫生、食品、环境等领域[1-4]。但对于利用氢化物发生-原子吸收光谱法测定粗铜中砷、锑、铋等元素的方法未     

微波消解-流动注射-氢化物发生-原子吸收法测定中药材中的汞和砷

建立了用微波消解处理样品,流动注射-氢化物发生-原子吸收法检测中药材中汞和砷含量的方法。汞在0.002～0.02mg/L浓度范围内线性良好,检出限为0.0004mg/L;砷在0.02～0.16mg/L浓度范围内线性良好,检出限为0.001mg/L,汞和砷的线性相关系数均大于0.9999;汞、砷的回收率分别为85.0%～93.8%、89.4%～102.0%,相对标准偏差分别为5.5%和4.1%。     

流动注射氢化物发生原子荧光光谱法测定土壤中铅

土壤中铅的测定,以往多用石黑炉[1]或氢化物发生[2]原子吸收光谱法,本文通过试验表明,应用流动注射氢化物发生原子荧光光谱法测定,使方法更为简便、快速,结果准确可靠.     

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%).     

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.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.