铬(Ⅵ)-硫脲体系的极谱吸附波及其用于土壤中总铬和有效铬(Ⅵ)的测定

在稀硫酸介质中，在加热条件下．铬（Ⅵ）氧化硫脲的产物在单扫示波极谱仪上产生一灵敏的吸附波，峰电位为-0．33V（vs.SCE），检出限为0．1μg／L．铬（Ⅵ）浓度在0．2～200μg／L范围内与峰电流呈线性关系。本法用于土壤中总铬和有效铬（Ⅵ）的测定，结果满意。     

血清蛋白-荧光素复合物单扫极谱波与应用

在0．08mol／L的HAc中，荧光素与牛血清白蛋白(BSA)或人血清白蛋白(HSA)相互作用形成复合物。复合物使荧光素在-0．58V(vs．SCE)处的还原峰电流增大，峰电流的增大值与加入的BSA或HSA的浓度在一定的范围内呈线性关系。BSA在2—24μg／mL范围内呈线性关系，检出限为1μg／mL；HSA在2—22μg／mL范围里呈线性关系，检出限为0．8μg／mL。应用该法测定了人血清蛋白样品，结果令人满意。     

单扫描极谱法测定果、蔬中有机磷农药残留量

提出了在0．40mol/L氢氧化钠底液中对碱解后的有机磷农药进行单扫描极谱测定的方法。于起始电位－0．30V（vs SCE)进行阴极化扫描时有产生一灵敏导数波,峰电位为－0．53V（vs SCE)。并获得了辛硫磷残留量检测的最佳条件。在此条件下检测有机磷农药的线性范围分别为：辛硫磷0．12－160μg/mL,甲基对硫磷0．5－200μg/mL,水胺硫磷0．20－160μg/mL,甲胺磷0．1－1．0ng/mL,氧化乐果0．09－160μg/mL。     

单扫描示波极谱法连测五味子、榛蘑中的铜和锌

研究了在HCl-KSCN底液中用单扫描示波极谱法连续测定五味子、榛蘑中铜和锌的方法。在此底液中,铜、锌分别在-0．42V(vs．SCE)、-1．03V(vs．SCE)处产生一敏锐的二阶导数波,检出限分别为0．005、0．01μg／mL,线性范围分别为0．01～8．00μg／mL,0．01～10．00μg／mL。应用本方法测定了五味子、榛蘑中的铜和锌,方法回收率为96．5％～101．8％。     

血清白蛋白的铅(Ⅱ)-抗坏血酸络合吸附波法测定

在pH9．2的H3BO3-NaOH缓冲溶液中,血清白蛋白使铅(Ⅱ)-抗坏血酸络合物在-0．51V(vs．SCE)处的络合吸附波电流降低,电流降低值与加入的牛血清白蛋白(BSA)或人血清白蛋白(HSA)的浓度在一定范围内呈线性关系。BSA在2～38μg／mL范围内,HSA在2～35μg／mL范围内呈线性关系,检出限均为1μg／mL。应用该法测定了人血清样品中蛋白质的含量,结果令人满意。     

锑(Ⅲ)-溴邻苯三酚红导数示波极谱法测定锌浸出液中的锑

在pH2．5的硫酸介质中，锑(Ⅲ)与溴邻苯三酚红生成的络合物产生一个灵敏的导数极谱波，其导数波峰值电位为-0．56V(vs．SCE)，线性范围0．0l～0．5μg／mL，许多离子不干扰测定，不需要分离与富集，直接测定锌浸出液中不同含量的锑。     

铅与呋喃甲酰基吡唑啉酮、联吡啶三元配合物吸附波的研究

在pH=3．51的HAc-NaAc介质中,测得1-苯基-3-甲基4-(α-呋喃甲酰基)吡唑啉酮-5(HPMαFP)与2,2′-联吡啶(dipy)合铅三元配合物的灵敏极谱波(-0．73 V(vs．SCE))。铅浓度在0．002～9×10-6 g／mL范围内与峰电流分段呈良好的线性关系,检测下限为2．0×10-9 g／mL。采用多种电化学方法研究了极谱波的性质和电极反应机理。结果证明,-0．73 V处的极谱波为多元配合物吸附波,峰电流由中心离子Pb2 还原产生。根据直线法测得多元配合物组成为n(Pb2 ):n(dipy):n(HPMαFP)=1:1:1,表观稳定常数为5．06×106。体系用于粗盐、蔗糖和化妆品中铅测定,标准回收率为99．3％～100．4％。     

极谱法检测碳酸锂药片中锂

Li+在p H 10.5 B-R缓冲溶液中能抑制钙指示剂和H2O2形成络合物,1.0×10-4mol/L钙指示剂和1.2%的H2O2在0.16 mol/L的B-R缓冲溶液中,于起始电位-0.0 V(vs.SCE),峰电位(Ep)-0.628V(vs.SCE)处产生一灵敏的极谱还原波,Li+能与H2O2和钙指示剂结合使络合物的峰电流下降,该波的二阶导数峰电流(Ip")与Li+质量浓度在0.8~800μg/m L范围内呈良好的线性关系,检出限为0.3146μg/m L。回收率为94.4%~102.9%。方法已用于碳酸锂片中Li+的测定,并讨论了其机理。电极反应物是钙指示剂和H2O2的络合物。     

线性扫描极谱法检测环境水样中四环素

基于四环素在pH=5.5的柠檬酸-柠檬酸钠缓冲溶液中可产生一灵敏的还原峰,建立了一种测定四环素的极谱新方法。在优化条件下,于起始电位-0.9 V(vs.SCE),峰电位-1.4V(vs.SCE),四环素浓度分别在0.1~30、30~90μg/mL范围内与峰电流呈现良好的线性关系,检出限为0.0024μg/mL。该方法直接用于环境水样中四环素的检测,回收率为97.8%~102.9%。用线性扫描极谱法研究了检测体系的电化学行为,证明了极谱波为不可逆还原吸附波,并讨论了电极反应机理。     

单扫描示波极谱法测定针剂中头孢呋辛钠含量

在稀HCl介质中,头孢呋辛钠在滴汞电极上于-0.47V(vs.SCE)处产生一灵敏的极谱还原峰,头孢呋辛钠在6～600μg/mL范围内与其峰电流呈线性关系。据此,建立了用单扫描示波极谱法测定药物中头孢呋辛钠含量的新方法。方法检出限为0.35μg/mL。该法用于实际药品测定,相对标准偏差(RSD)为0.45%～0.97%(n=8),加标回收率为98.04%～103.64%。     

Solid-supported [2+2+2] cyclotrimerizations

The transition-metal-catalyzed [2+2+2] cyclotrimerization of a diyne and an alkyne provides a convergent route to highly-substituted aromatic rings. This reaction possesses distinct drawbacks, especially low chemo- and regioselectivities, which hamper its application in combinatorial synthesis. These problems have been solved by the development of solid-supported [2+2+2]-cycloaddition reactions. If conducted on a solid-support, this reaction enables rapid combinatorial access to diverse sets of carbo- and heterocyclic small-molecule arrays. The scope of this methodology has been investigated by examining different immobilization strategies, different diyne precursors, and a variety of functionalized alkyne reaction partners. Overall, isoindoline, phthalan, and indan libraries were assembled in good to excellent yields and with high purities.     

Alkenes in [2+2+2] Cycloadditions

Participation of alkenes and allenes in [2+2+2] cycloaddition reactions has attracted much attention recently. This version of the well‐established alkyne cyclotrimerization renders interesting products, such as cyclohexadienes and other polycycles, through cascade processes. Many mechanistic variations are observed when using certain metal complexes as catalysts. The frequent generation of stereogenic centers has prompted the development of efficient asymmetric versions. This Minireview summarizes the efforts reported to date on the use of double bonds as partners in [2+2+2] cyclotrimerizations.     

Intracellular Ruthenium-Promoted (2+2+2) Cycloadditions

Metal-mediated intracellular reactions are becoming invaluable tools in chemical and cell biology, and hold promise for strongly impacting the field of biomedicine. Most of the reactions reported so far involve either uncaging or redox processes. Demonstrated here for the first time is the viability of performing multicomponent alkyne cycloaromatizations inside live mammalian cells using ruthenium catalysts. Both fully intramolecular and intermolecular cycloadditions of diynes with alkynes are feasible, the latter providing an intracellular synthesis of appealing anthraquinones. The power of the approach is further demonstrated by generating anthraquinone AIEgens (AIE=aggregation induced emission) that otherwise do not go inside cells, and by modifying the intracellular distribution of the products by simply varying the type of ruthenium complex.     

A photoionization study of the charge transfer reactions: Xe+ + O2 → O+2 + Xe and O+2 + Xe → Xe+ + O2

Photoionization mass spectrometer techniques have been employed to study the charge transfer reactions: Xe⁺ + O₂ → O⁺₂ + Xe and O⁺₂ + Xe → Xe⁺ + O₂. The results show the reaction of Xe⁺(²P_{$\text{3}\text{2}$}) ions with O₂ molecules is much more efficient than the reaction of Xe⁺(²P_{$\text{1}\text{2}$}) ions with O₂ molecules. The charge transfer reaction of O⁺₂ ions with Xe atoms was detected for O⁺₂ ions in the a ⁴Π_u state.     

Formal [(2+2)+2] and [(2+2)+(2+2)] nonconjugated dienediyne cascade cycloadditions

[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.     

Studies on Synthetic Inorganic Ion Exchangers-III Quantitative Separations of Mg2+ -Pb2+, Zn2+ - Pb2+ Cu2+ - Pb2+, Al3+ - Pb2+, Zn2+ - Cd2+, and Mg2+ - Cd2+ on Lead Antimonate Columns

Abstract

A new inorganic ion exchanger, lead antimonate has been synthesized having an Pb:Sb ratio of 1:5 and cation exchange capacity of 1.46 mequiv./g. It is fairly stable in water and dilute solutions of acids, bases and salts. Ion distribution studies on twenty metal ions have been determined on this gel at pH 1,2,3 and 5. The following mixtures have been separated: Mg²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Cu²⁺ - Pb²⁺, Al³⁺ - Pb²⁺, Zn²⁺ - Cd²⁺ and Mg²⁺ - Cd²⁺. Mg²⁺ and Al³⁺ were removed with 0.4 M ammonium nitrate, Cu²⁺ and Zn²⁺ with 0.4 M ammonium nitrate + 0.1M nitric acid (1:1), Pb²⁺ with 0.5M nitric acid and Cd²⁺ with 0.25M nitric acid. A tentative structure of this material is proposed on the basis of chemical analysis, pH titrations, thermogravimetry and IR spectrophotometry.     

Tethered 2 + 2 + 2 cycloaddition reactions of cobalt-cycloheptyne complexes

Cycloheptyne-dicobalt hexacarbonyl complexes, substituted by propargylic ether functions, undergo 2 + 2 + 2 cycloaddition reactions with alkynes to give tricyclic benzocycloheptanes; an all-intramolecular version of this transformation is also possible.     

Rhodium‐Catalyzed [3+2+2] and [2+2+2] Cycloadditions of Two Alkynes with Cyclopropylideneacetamides

It has been established that a cationic rhodium(I)/H₈‐binap complex catalyzes the [3+2+2] cycloaddition of 1,6‐diynes with cyclopropylideneacetamides to produce cycloheptadiene derivatives through cleavage of cyclopropane rings. In contrast, a cationic rhodium(I)/(S)‐binap complex catalyzes the enantioselective [2+2+2] cycloaddition of terminal alkynes, acetylenedicarboxylates, and cyclopropylideneacetamides to produce spiro‐cyclohexadiene derivatives which retain the cyclopropane rings.