酸度对氢化物发生-原子荧光光谱法测定砷镉汞铅硒的影响

对用氢化物发生-原子荧光光谱法测定砷、镉、铅、汞、硒五元素时,溶液酸度对相关元素荧光强度的影响进行了试验,并提出了测定各元素时的最佳条件,所述酸度实际是指原子化前试液的综合酸度。试验结果表明,测定铅的溶液酸最严格,应控制在cHNO30．20～0．22 mol·L-1之间,与此相比,测定镉的酸度范围较宽,可允许在cHCl 0．20～0．31 mol·L-1范围内。而对砷、硒、汞的测定,酸度的影响最小,依次在cHCl>0．1 mol·L-1,cHCl>0．12 mol·L-1及cHNO3>0．16 mol·L-1的酸度条件下均能获得满意结果。     

CVG-ICP-AES法测定饮用天然矿泉水中痕量铅和汞

自制化学蒸气发生器并建立了KBrO3KBr K3Fe(CN)6HCl KBH4的CVG ICP AES同时直接测定饮用天然矿泉水中痕量铅和汞的方法,该方法提高了灵敏度,改善了检出限。方法的检出限分别为0.7μg·L-1(Pb220.353nm),0.1μg·L-1(Hg184.950nm),相对标准偏差分别为0.8%～7.8%(Pb)和0.5%～6.2%(Hg);回收率分别为90.0%～100.0%(Pb)和92.8%～108.0%(Hg)。方法完全能满足饮用天然矿泉水中痕量铅和汞的分析。     

原子簇化合物的结构规则与化学键性质

本文从形成双中心键,三中心键和四中心键时,成键与相应的反键之间数目关系的三个基本假定出发,推导出封闭型、巢型和网型硼烷的Wade规则及其分子中双中心键、三中心键和四中心键的具体数目。进而将Wade规则推广,使之适用于包括具有戴帽结构的杂硼烷和推广到用B原子稠合成的稠合型硼烷。最后用于讨论过渡金属羰基化合物和具有密堆积型过渡金属羰基化合物的结构规则。     

氢化物发生-原子荧光光谱法测定人血液中铅砷汞镉

现代社会的人类活动使环境受到一定的污染，其中重金属污染对人体健康有一定影响。本法采用氢化物发生一原子荧光光谱法（HGAFS）测定铅、砷、汞和镉，方法具有检出限低、精密度好等优点。     

两次双波长分光光度法测定铅和汞

基于卟啉试剂ＴＡＰＰ与Ｐｂ￣（２＋）、Ｈｇ￣（２＋）在碱性介质中有灵敏的显色反应，建立了两次双波长分光光度法同时测定Ｐｂ、Ｈｇ的新方法，摩尔吸光系数分别为４．５９×１０￣５和４．３２×１０￣５ｍｏｌ￣（－１）·ｃｍ￣（－１）·Ｌ；可同时测定１：５～１０：１范围内的Ｐｂ和Ｈｇ，用于水中Ｐｂ和Ｈｇ的同时测定，结果满意。     

原子荧光光谱法测定新疆薰衣草中的铅、砷和汞

采用原子荧光光谱法对新疆不同产地薰衣草样品中的铅、砷和汞3种重金属元素的含量进行了测定。结果表明,测定薰衣草中的铅、砷和汞元素的线性范围分别在0.1~20μg·L-1、0.5~50μg·L-1和0.1~10μg·L-1之间,检出限分别为0.05μg·L-1、0.03μg·L-1和0.05μg·L-1,相对标准偏差(RSD)≤3.03%(n=6),各元素的加标回收率在97.0%~103.0%之间。该方法快速、简便、数据准确可靠。     

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...     

微波消解-原子吸收光谱法测定口红中的铅、汞

建立了微波消解–原子吸收光谱法测定口红中铅、汞的方法。以微波消解装置进行口红样品预处理,以石墨炉原子吸收光谱法进行铅含量测定,以冷原子吸收光谱法进行汞含量测定。铅在0.00～2.50 mg/L范围内的线性方程为y=0.022 3x+0.000 8,r=0.999 3,检出限为0.003 mg/L。汞在0～500 ng/L范围内的线性方程为y=400.12x+52.3,r=0.999 9,检出限为6 ng/L。铅、汞测定结果的相对标准偏差分别为0.87%～2.6%,0.65%～2.41%(n=6),加标回收率分别为121%～126%,100%～102%。该方法以单消解方式进行样品前处理,再以该消解液分别进行两种元素含量分析,可提高分析效率,适用于化妆品中金属含量分析。     

微波消解-氢化物发生-原子荧光光谱法同时测定土壤及生物样品中铅和汞

应用氢化物发生-原子荧光光谱法测定了土壤及生物样品中铅和汞。样品用硝酸4mL及过氧化氢1mL按微波消解仪的工作参数进行消解,消解后溶液定容至25mL供测定。用30g·L-1柠檬酸溶液和硝酸(1+99)溶液的混合液作载流,根据铅(Ⅱ)离子的反应和试液对酸度的要求,选用含15g·L-1硼氢化钾,10g·L-1铁氰化钾和20g·L-1氢氧化钾的混合溶液作为还原剂。方法的检出限(3s/k)为0.512μg·L-1(铅)和0.067μg·L-1(汞)。应用此方法分析了3种实样并进行加标回收试验,测得回收率分别在91.0%~97.0%(铅)和88.0%~95.5%(汞)之间。     

氢化物原子荧光法同时测定虫草中的痕量铅和汞

采用断续流动氢化物发生器,以碱性铁氰化钾为氧化剂,在柠檬酸介质中使铅和汞分别产生铅烷和汞蒸气。采用氢化物发生原子荧光法同时测定痕量铅和汞。考察了共存元素的干扰情况,在选定最佳工作条件下测得铅和汞的检出限分别为3.00×10-4μg/mL和3.00×10-5μg/mL,相对标准偏差分别为2.3%和1.0%(n=11)。将该法应用于虫草中痕量铅和汞的同时测定,加标回收率分别为94.5%和95.3%。     

The Nature of Bonding in IrC

Thetheoreticalstudyofsmallmoleculescontainingtransitionmetalatomsisoneofthemostactiveareasinquantumchemistry'becauseofthemanyimportantmaterialsandcatalyticapplicationsofthetransitionmetalsandalsotheirimpoytanceinbiology.Therehavebeenveryextensivestudiesonfirstandsecondrowtransitionmetalhydrides"',oxides4-6andthetransitionmetaldimers7-9.Buttheoreticalstudiesonthethirdrowtransitionmetalcompoundsareratherscarceg-11.Iridiumisanimportantelementforcatalyticreactions,andtheknowledgeoftheinteractionbe…     

过渡金属络合物成键本质分析的常用方法

过渡金属络合物中过渡金属与配体间所形成的化学键的成键本质,可以在理论化学基础上,采用定量的方法进行分析。本文重点以铁羰基络合物为例,对常用的分析方法,如自然键轨道方法(NBO)、电荷分解分析(CDA)、分子中的原子(AIM)拓扑分析方法以及ETS和EDA能量分解方法等,在应用中的优缺点进行了分析和评述。借助于这些方法提供的电荷、能量和电子密度等配分项可以深刻认识和理解过渡金属-配体间形成的化学键的成键本质。     

1,4-二氧六环和氨分子氢键团簇的从头算

在不同基组水平上,对１,４－二氧六环和氨分子氢键团簇体系进行了从头算分子转道法研究,优化得到中性团簇,离子团簇和碎片离子（质子化团簇离子和非质子化团簇离子）平衡几何构型,研究结果表明：中性团簇最稳定构型为Ｒ－ＨＮ２－ＨＮＮ２（Ｒ：１,４－二氧六环）,离子团簇由于发生质子转移,其构型与中 团簇有较大的淡同,两类碎片离子Ｒ（ＮＨ３）＋和Ｒ（ＮＨ３）Ｈ＾＋与中性团簇Ｒ（ＮＨ３）的结构也有所不同     

Electron‐Deficient Triborane and Tetraborane Ring Compounds: Synthesis,Structure, and Bonding

Electron‐deficient small boron rings are unique in their formation of σ‐ and π‐delocalized electron systems as well as the avoidance of “classical” structures with two‐center‐two‐electron (2c,2e) bonds. These rings are tolerant of several skeletal electron numbers, which makes their redox chemistry highly interesting. In the past few decades, a range of stable compounds have been synthesized with various electron numbers in their B₃ and B₄ cores. The electronic structures were evaluated by quantum‐chemical calculations. On the other hand, the chemistry of these rings is still very much underdeveloped, being generally limited to the protonation and redox reactions of individual systems. The linkage of several B₃ and/or B₄ ring systems should give compounds with attractive electronic properties, thus leading the way to novel boron‐based materials. By summarizing important experimental and theoretical results, this Review intends to provide the basis for the exploration of the chemistry of these rings and, in particular, their integration into larger molecular architectures.     

Clusters of Valence Electron Poor Metals—Structure,Bonding, and Properties

Metals in low oxidation states are capable of forming metal–metal bonds. An attempt has been made to classify the numerous phases and structures occurring in such metal-rich systems of valence electron poor metals in some sort of order from a rather general point of view. With this purpose in mind, clusters of these elements, their different types of interconnections, and their condensation via shared metal atoms, which finally leads to extended M? M bonded structures, are described. Interstitial atoms play an important role in stabilizing electron deficient clusters, and can actually lead to the loss of all M? M bonds. Surprising similarities emerge between apparently very different systems as the metal-rich oxides of alkali metals, the oxides, halides, and chalcogenides of d transition metals, and the halides and carbide halides of the lanthanoids.     

Iodine(III) Derivatives as Halogen Bonding Organocatalysts

Hypervalent iodine(III) derivatives are known as versatile reagents in organic synthesis, but there is only one previous report on their use as Lewis acidic organocatalysts. Herein, we present first strong indications for the crucial role of halogen bonding in this kind of catalyses. To this end, the solvolysis of benzhydryl chloride and the Diels–Alder reaction of cyclopentadiene with methyl vinyl ketone served as benchmark reactions for halide abstraction and the activation of neutral compounds. Iodolium compounds (cyclic diaryl iodonium species) were used as activators or catalysts, and we were able to markedly reduce or completely switch off their activity by sterically blocking one or two of their electrophilic axes. Compared with previously established bidentate cationic halogen bond donors, the monodentate organoiodine derivatives used herein are at least similarly active (in the Diels–Alder reaction) or even decidedly more active (in benzhydryl chloride solvolysis).     

Computational Study of Hydrogen Bonding in Substituted Phenol‐Acetonitrile‐Water Clusters

The calculations for a water‐acetonitrile‐substituted phenols system and the comparison with the experimental parameters will be given. Here we study change in the nature of the interactions into the system with donor and acceptor electron substituents on the phenolic ring, the structures, relative energies and harmonic frequencies. The conformers showed a significant difference in the OH and CN band shift depending on the type of the hydrogen bond formed and the position of the substituent on the phenolic ring. The cyclical hydrogen bonds between water‐acetonitrile and substituted phenol OH are important evidence of the relative stability in the system under study.     

Highly Active Halogen Bonding and Chalcogen Bonding Chloride Transporters with Non-Protonophoric Activity

Synthetic anion transporters show much promise as potential anti-cancer agents and therapeutics for diseases associated with mis-regulation of protein anion channels. In such applications high activity and anion selectivity are crucial to overcome competing proton or hydroxide transport which dissipates cellular pH gradients. Here, highly active bidentate halogen bonding and chalcogen bonding anion carriers based on electron deficient iodo- and telluromethyl−triazole derivatives are reported. Anion transport experiments in lipid bilayer vesicles reveal record nanomolar chloride transport activity for the bidentate halogen bonding anion carrier, and remarkably high chloride over proton/hydroxide selectivity for the chalcogen bonding anionophore. Computational studies provide further insight into the role of sigma-hole mediated anion recognition and desolvation at the membrane interface. Comparison with hydrogen bonding analogues demonstrates the importance of employing sigma-hole donor motifs in synthetic anionophores for achieving both high transport activity and selectivity.     

Bonding Analysis of Square-Antiprismatic and Fused Square-Antiprismatic Copper(I)-Selenium Clusters

The electronic structure of the Cu_2(4n+2)Se_4n+2(PH₃)₈ (n = 1–4) D _4h series of model clusters has been analyzed by means of density functional theory calculations. The fused square antiprismatic structure of the metal framework is found to be always preferred over the fused cuboctahedral one because it reinforces the Cu-P bonds. Thus, the presence of the terminal phosphine ligands tends to strengthen the Cu...Cu (d¹⁰...d¹⁰) bonding by mixing bonding combinations of the vacant Cu 4s and 4p orbitals into the occupied 3d combinations. The calculations indicate that the compounds corresponding to n = 3 and 4 should be easily two-electron-reduced, leading to stable dianionic species.     

Tuning the Halogen Bonding Strength of Cyclic Diaryliodonium Salts

Diaryliodonium(III) salts have recently received increasing interest as a new class of strong halogen bonding noncovalent organocatalysts. Even though this utilization of their Lewis acidity has only been investigated in few studies, their high potential in comparison to classical monovalent iodine based XB donors has become very apparent. So far, only acyclic and cyclic five-membered core structures have been used, and titration studies have shown the latter to be superior in terms of binding constants towards Lewis bases. Herein, we now compare the Lewis acidity and activity of these five-membered iodolium salts with those of six-membered iodininium derivatives. X-Ray structural analyses, ITC measurements and the reaction kinetics of a Ritter-type solvolysis reaction in wet acetonitrile (a typical halogen bond donor benchmark reaction) all demonstrate that iodolium salts are stronger halogen bond donors and catalysts than iodininium salts. Subsequently, we were able to improve the activity of both core structures significantly by introducing electron-withdrawing substituents.