火焰原子吸收光谱法直接测定食用菌中的铅和镉

采用火焰原子吸收法直接测定了食用菌中铅和镉的含量。方法灵敏、准确，测定时无须富集、萃取，操作简便，快速，铅和镉的相对标准偏差分别在3．3％～7．3％和3．1％～7．5％之间。回收率在94％～106％和95％～105％之间；检出限为0．016mg/L和0．008mg/L。     

微波消解冷原子荧光法测定市售猪肉中的痕量汞

采用微波消解，冷原子荧光法测定了猪肉中的痕量汞。汞的回收率在90．7％～98．8％之间；相对标准偏差（RSD）2．62％；检出限为0．010μg/mL；线性范围0～12μg/mL。     

石墨炉原子吸收分光光度法测定茶叶中的铅

采用石墨炉原子吸收分光光度法测定了产自福建等地茶叶中的铅含量。方法的线性范围为0—80μg/L，回收率达91．7％-101．5％，相对标准偏差1．47％-3．88％。茶样检测结果表明，铅合格率为92．0％；不同茶类铅含量前3位由高到低依次为绿茶，乌龙茶，红茶；各类茶铅含量平均值为1．069mg／kg。     

同时测定癌症病人血液中锌镉铅铜的微分脉冲阳极溶出伏安法

用微分脉冲阳极溶出伏安法同时测定癌症病人血液中的锌、镉、铅和铜，以为癌症与这4种微量元素在血液中含量的相关性研究提供实验数据；癌症病人血液用硝酸-高氯酸消化，消化后的白色固体加水溶解，以0．100mol/L硫酸铵为底液，在三电极体系中进行测定，以峰电位定性，峰电流定量；用该法测定了3种癌症病人血液中的锌、镉、铅和铜，相对标准偏差为2．9％—3．3％(n＝6)，加标回收率为98％—110％；该法不用除氧、干扰少、分辨率好、准确度高，适用于临床血液中锌、镉、铅和铜的测定和研究。     

石墨炉原子吸收光谱法测定蔬菜中铅、镉的含量

选择8种新鲜蔬菜，用硝酸-高氯酸消解后以石墨炉原子吸收光谱法测定其中铅、镉的含量。对测定的工作条件和样品的预处理方法进行了探讨。铅、镉的线性回归方程分别为A=0．00062c 0．004，A=0．00366c 0．0350。测定结果的相对标准偏差分别为5．99％、5．33％，回收率分别为88．5％、107％，检出限分别为2．24、0．472μg/kg。     

流动注射-氢化物发生原子发射光谱法测定板蓝根中的有害元素

使用流动注射-氢化物发生-电感耦合等离子体原子发射光谱联用技术同时测定中药板蓝根中微量有害元素砷、铅、镉和汞的含量。对影响分析信号的主要工作条件进行了选择和优化。砷、铅、镉和汞的检出限分别为0．51、1．5、0．33和0．25μg／L;其回收率分别为98%、101%、103％和108％。本法用于中药板蓝根中微量有害元素的分析,结果满意。     

微波消解-电感耦合等离子体原子发射光谱法测定电子电气产品陶瓷和玻璃中的铅、镉、铬和汞

采用微波消解技术，将电子电气产品中陶瓷和玻璃样品用HNO3-氟硼酸-H2O2在210℃的温度下加热约Ih溶解后，用全谱直读ICP—AES同时测定电子产品中陶瓷和玻璃里的铅、镉、铬和汞，方法的检出限为0．0015～0．012μg／mL。方法的回收率和精密度分别为90．5％～97．5％和0．16％-3．74％。可用于电子电气产品中陶瓷和玻璃里铅、镉、铬和汞的日常检验。     

ICP-MS法测定PVC-U饮水管材(件)中的痕量铅、镉、锡、汞

采用电感耦合等离子体质谱(ICP—MS)法测定硬聚氯乙烯(PVC—U)饮水管材(件)中的痕量铅、镉、锡、汞，对影响测量结果的因素进行了分析。利用该法测定铅、镉、锡、汞的检出限分别为0.0028、0．0025、0．0052、0．0033μg/L，回收率为84．60％～94.30％，测定结果的相对标准偏差小于4．23％。     

断续流动注射-催化原子荧光光谱法测定碘

基于碘对亚砷酸-硫酸铈的催化反应，断续流动进样，用氢化物发生．原子荧光光谱法直接测定As(Ⅲ）的浓度变化，建立了微量碘间接测定的方法。在实验条件下，碘离子的线性范围为0．80μg/L；相对标准偏差为2．3％；检测限为4μg/L．加标回收率为92．5％-98．2％。测定结果与硫氰酸铁-亚硝酸催化动力学法相比具有很好的一致性。     

石墨炉原子吸收分光光度法测定大气颗粒物中的镉

将大气颗粒物样品采集在有机滤膜上(或滤筒中)，用硝酸、高氯酸消解，以石墨炉原子吸收分光光度法测定其中镉的含量。在0．00～8．00μg/L范围内对镉的质量浓度与吸光度数据进行回归，得线性方程为A：0．016 0．041X，相关系数r=0．9991，回收率为90％～94％，测定结果的相对标准偏差为2．1％～7．5％，检出限为0．366μg/L，该方法适用于大气和固定污染源排气中镉的测定。     

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.