石墨炉原子吸收光谱法测定生物样品中微量锗

采用钼酸铵浸渍处理石墨管 ,研究了苯基荧光酮为螯合剂 ,四氯化碳为萃取剂 ,N ,N 二甲基甲酰胺 (DMF)为反萃取剂的萃取富集锗的新方法 ,用硝酸镍作为基体改进剂 ,石墨炉原子吸收光谱法直接测定各种生物样品中微量锗。方法绝对灵敏度 (1%吸收 )为 1.67× 10 - 11g ,相对标准偏差 3.5 4 %～ 6.15 % ,回收率为 96%～ 10 2 %     

电热原子吸收光谱测定锗时钯的基体改进作用及在食品分析中的应用

本文建立了钯为基体改进剂,电热原子吸收法测定食品中微量锗的方法。该法的检测限为22×10~(-13)g,特征量为8×10~(-13)g。讨论了钯基体改进剂提高锗灵敏度和灰化温度的机理,认为主要是灰化阶段锗与钯在石墨管表面发生固相反应的结果。     

钨钽石墨管原子吸收光谱法直接测定土壤中痕量钕和钪

本文采用一种新型石墨管原子化器—钨钽石墨管,测定钕和钪。与普通热解涂层石墨管相比,灵敏度提高五倍多,1％吸收灵敏度钕为3.2×10~(-10)克,钪1.0×10~(-11)克;消除了记忆效应,提高了工作效率;原子化温度降低100多度,管的使用寿命延长1～3倍,达200次以上,测定精密度在5％以内;抗基体元素的干扰能力较好。土壤中20ppm以上的钕和200ppb以上的钪无需预分离富集,可以直接测定,结果与中子活化法一致。该方法简便、准确。     

氯化物发生原子吸收光谱法测定痕量镉、铅和镍——Ⅰ、装置及操作条件的选择

本文应用氯化物发生原子吸收光谱法这一新技术,在自行设计的装置上分别对镉、铅和镍进行了考察;选出了合适的操作参数。它们的测定灵敏度(1％吸收)分别为7×10~(-10)g、7×10~(-9)g和2×10~(-9)g;10次测定的相对标准偏差分别为6.0％、7.6％和8.0％。该方法装置简单,测定灵敏度较高,预计可测近40种元素。     

石墨炉AAS中气体直接进样技术的研究——氢化物法测定As、Sb、Bi、Sn、Ge和Pb

本文提出将气体样品经石墨炉的载气入口由载气直接引入石墨炉的技术,实现了石墨炉原子吸收光谱中气体样品的直接进样测定,并成功地应用于氢化物气体的分析,测定了砷、锑、铋、锡、锗和铅,其灵敏度为2.0×10~(-9)g～8.1×10~(-10)g;检出限为2.1×10~(-9)g～6.0×10~(-11)g;线性范围上限为30μg/1～400μg/1;精密度(R.S.D)为0.76%～2.4%。     

石墨炉原子吸收光谱法测定冶金材料中痕量钛

本文研究了不同石墨管测钛的特点,用热解石墨管测定钛灵敏度较高,并可消除某些共存元素的干扰。探讨了在高温石墨炉中钛的原子化机理,提出了TiO_2被碳还原的可能性。方法适用于测定冶金材料中痕量钛,测定钛的特征含量可达3.76×10~(-10)克/1%吸收,相对标准偏差为3.8%。该法准确、简便、快速。     

锗-苯基荧光酮-吐温-80-明胶增溶光度法测定人发中微量锗

在盐酸介质中,以苯基荧光酮为显色剂,吐温-80为表面活性剂,明胶为稳定剂,用增溶胶束分光光度法测定微量锗。探讨了测定微量锗的最佳显色条件和光度测定条件。配合物的最大吸收位于510 nm波长处,锗含量在0.5~10μg/50 mL范围内符合比耳定律,其摩尔吸光系数ε=1.18×105L.mol-1.cm-1,具有较高的灵敏度和选择性,用于人发中锗含量的测定,测定结果的RSD小于0.9%,加标回收率在95.9%~105.9%。     

聚乙烯吡啶化学修饰电极预富集-石墨炉原子吸收法测定酒石酸锑钾的研究

本文研究了聚乙烯吡啶(PVP)化学修饰电极预富集——石墨炉原子吸收法测定酒石酸锑钾的方法。结果表明,在 pH 为3.5的 HCl 介质中,酒石酸锑钾浓度在5.4×10~(-8)～2.2×10~(-6)g/ml 范围内,与吸光度值呈良好的线性关系。对1.1×10~(-6)g/ml 的酒石酸锑钾溶液平行测定9次,相对标准偏差为4.9%,最低检测限为1.6×10~(-8)g/ml。17种异离子及有机物不干扰测定,回收率在97～103%之间,结果令人满意。     

二甲氧基羟基苯基荧光酮光度法测定生物样品中锗

研究了二甲氧基羟基苯基荧光酮光度法测定锗。在H3PO4 介质中 ,TritonX 10 0存在时 ,锗与二甲氧基羟基苯基荧光酮形成 1∶2橙红色络合物 ,最大吸收在 5 0 5nm波长处 ,表观摩尔吸光系数为 1.8× 10 5L·mol- 1·cm- 1,并且具有灵敏度高、选择性好的特点。当锗含量在 0～ 7μg/2 5ml范围内符合比耳定律。已用于茶叶、党参和药物中锗的测定     

鲁米诺-AuCl4^- -H2O2体系化学发光反应的研究——-矿石中痕量金的测定

液相化学发光分析法是一种灵敏度很高的分析方法。有人曾用此法以测定痕量金,检测极限1×10~(-8)g/mL金,工作曲线的线性范围1×10~(-8)～1×10~(-7)g/mL金。本文首次提出并用自制液相化学发光分析仪(图1)研究了鲁米诺-AuCl_4~--H_2O_2液相化学发光体系,确定了用这一体系测定金的最佳条件,制定了测定的具体方法。检测极限4×10~(-11)g/mL金,工作曲线的线性范围1×10~(-10)～1×10~(-5)g/mL金,相对标准偏差     

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.