氟化电热蒸发—ICP—AES直接测定生物试样中痕量镧

采用聚四氟乙烯（ＰＴＦＥ）为氟化剂，以悬浮体制样ＥＴＶ－ＩＣＰ－ＡＥＳ直接测定固体生物试样中的难熔稀土元素Ｌａ，研究了粒度效应和Ｌａ的氟化蒸发行为。在优化实验条件下，方法的检出限为２．０ｎｇ／ｍＬ，相对标准偏差为４．５％。该方法简便、灵敏，无需进行化学前处理，可用于固体生物试样的直接分析，分析结果与参考值吻合。     

氟化电热蒸发－ICP－AES直接测定生物试样中痕量镧

采用聚四氟乙烯（ＰＴＦＥ）为氟化剂，以悬浮体制样ＥＴＶ－ＩＣＰ－ＡＥＳ直接测定固体生物试样中的难熔稀土元素Ｌａ，研究了粒度效应和Ｌａ的氟化蒸发行为。在优化实验条件下，方法的检出限为２．０ｎｇ／同ｍＬ，相对标准偏差为４．５％。该方法简便、灵敏，无需进行化学前处理，可用于固体生物试样的直接分析，分析结果与参考值吻合。     

氢化物发生(HG)-ICP-AES测定中药漏芦中微量砷、锑、铋的研究

提出氢化物发生等离子体原子发射光谱（ＨＥ－ＩＣＰ－ＡＥＳ）值接测定中药漏芦中微量Ａｓ、Ｓｂ、Ｂｉ的方法。对影响分析信号的主要工作条件进行了选择和优化,对干扰元素及消除方法进行了考察。方法的检出限Ａｓ、Ｓｂ、Ｂｉ分别为２．７、３．４、２．８ｎｇ／ｇ,精密度（ＲＳＤ）为２．１％～５．０％,试样加入平均回收率为９２．５％～１０６．５％,本法用于中药漏芦的分析,结果满意。     

聚三氟氯乙烯化学改进剂在电热蒸发(ETV)-ICP-AES直接测定生物试样中微量钛的应用

本文首次提出以聚三氟氯乙烯（ＰＴＦＣＥ）为化学改进剂，应用于悬浮体制样ＥＴＶ－ＩＣＰ－ＡＥＳ直接测定固体生物试样中微量钛。实验采用５％ＰＴＦＣＥ，促进Ｔｉ的蒸发。方法的绝对检出限为２ｐｇ（按５σ计），ＲＳＤ为２．６％（ｎ＝５）。该法用于直接测定ＧＢＷ０８５０５茶叶粉末样品中的Ｔｉ，结果与参考值吻合，回收率为９７．３～１０５．４％。     

氟化电热蒸发／电感耦合等离子体原子发射光谱中的基体效应研究

本文系统研究了氟化电热蒸发／电感耦合等离子体原子发射光谱（ＥＴＶ－ＩＣＰ－ＡＥＳ）测定难熔元素的基体效应。与常规气动雾化（ＰＮ）－ＩＣＰ－ＡＥＳ中的基体效应比较，氟化ＥＴＶ－ＩＣＰ－ＡＥＳ中的基体效应更小。对难熔基体元素，由于基体和待测元素与氟化剂之间的竞争反应，随着基体浓度的增加，待测元素谱线强度降低；对常见基体元素，由于热循环中基体与待测元素之间的选择挥发，对待测元素的蒸发和传输过程无明显影响     

氟化电热蒸发（ETV）—ICP—AES直接测定生物试样中不同挥发性元素…

本文以聚四氟乙烯（ＰＴＥＥ）悬浮体为氟化剂，对悬浮体制样ＥＴＶ－ＩＣＰ－ＡＥＳ直接测定生物试样中不同挥发性元素钼、铜和镉的蒸发行为，影响因素及分析性能进行了比较研究，得出了相应的规律性。在选定实验条件下，本法测定Ｍｏ，Ｃｕ和Ｃｄ的检出限分别为０．４３、４．２和１４１ｎｇ／ｍＬ，ＲＳＤ分别为３．８％、４．２％和２．２％。提出的方法已应用于ＣＲＭ２８１生物标样分析，结果与参考值吻合。     

氟化电热蒸发（ETV）－ICP－AES直接测定生物试样中不同挥发性元素的比较研究

本文以聚四氟乙烯（ＰＴＥＥ）悬浮体为氟化剂，对悬浮体制样ＥＴＶ－ＩＣＰ－ＡＥＳ直接测定生物试样中不同挥发性元素锡、铜和镉的蒸发行为，影响因素及分析性能进行了比较研究，得出了相应的规律性。在选定实验条件下，本法测定ＭＯ，Ｃｕ和Ｃｄ的检出限分别为０．４３、４．２和１４１ｎｇ／ｍＬ，ＲＳＤ分别为３．８％、４．２％和２．２％。提出的方法已应用于ＣＲＭ２８１生物标样分析，结果与参考值吻合。     

电热蒸发进样电感耦合等离子体原子发射光谱（ETV－ICP－AES）联用技术研究

本文采用国产部件组装了一套ＥＴＶ－ＩＣＰ－ＡＥＳ仪器体系，对装置的连接及操作参数进行优化。深入系统地考察了分析物的蒸发过程和传输过程，提出了难熔元素的蒸发和传输机理。研究了ＥＴＶ－ＩＣＰ－ＡＥＳ中基体效应，提出了以聚四氟乙烯为氟化剂，氟化辅助ＥＴＶ－ＩＣＰ－ＡＥＳ测定难熔元素的新方法，应用于环境和生物标样中痕量元素分析，获得满意结果。     

聚三氟氯乙烯化学改进剂在电热蒸发（ETV）—ICP—AES直接测定生物试样…

本文首次提出以聚三氟氯乙烯（ＰＴＦＣＥ）为化学改进剂，应用于悬浮体制样ＥＴＶ－ＩＣＰ－ＡＥＳ直接测定固体生物试样中微量钛，实验采用５％，ＰＴＦＣＥ，促进Ｔｉ的蒸发，方法的绝对检出限为２ｐｇ（按５σ计），ＲＳＤ为２．６％（ｎ＝５），该法用于直接测定ＧＢＷ０８５０５茶叶粉末样品中的Ｔｉ，结果与参考值吻合，回收率为９７．３～１０５．４％。     

氟化电热蒸发－等离子体原子发射光谱直接测定生物试样中铜的研究

本文采用聚四氟乙烯（ＰＴＦＥ）为氟化剂，以悬浮体制样，ＥＴＶ－ＩＣＰ－ＡＥＳ直接测定生物固体粉末试样中的中等挥发性元素铜。详细研究了试样粒度对分析信号强度的影响，考察了铜在该技术中的蒸发行为以及影响氟化蒸发的主要因素，在优化的实验条件下，本法测定铜的检出限为４２ｐｇ，相对标准偏差为４．５％（ｎ＝１０，Ｃｕ浓度为０．２μｇ／ｍＬ），本法简单、快速、所得结果与参考值吻合很好。     

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.     

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%).     

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.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

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.