氯硝安定的电分析化学特性研究

用线性扫描、循环伏安、脉冲极谱、计时库仑和计时电位等方法研究了氯硝安定的电分析化学特性。在ＰＨ７．３０的缓冲溶液申，氯硝安定在－０．５５（Ｐ：）和－１．２０Ｖ处产生两个示波极谱波．利用ｐ１可测定痕量氯硝安定。线性范围为５．０×１０－８～１．０×１０－４ｍｏｌＬ－１，检测下限为３．０×１０－９ｍｏｌ·Ｌ－１。所提出的方法用于血清中氯硝安定测定，结果满意。     

Tetralone Esters as Intermediates for the Synthesis of Podophyllotoxin Derivatives Via Cyclopropanation of Chalcones

Cyclopropyl ester (8a-f) were synthesized by the cyclopropanation of chalcones (7a-e) in dry benzene using powdered sodium in 80-85% yield. Preparation of tetralone ester (4a-e), an intermediate for the synthesis of podophyllotoxin derivatives by Lewis acid (SnCl₄) catalyzed cyclization of (8a-e) is also described here.     

Kinetics and mechanism of electropolymerization of m-aminophenol

The kinetics and mechanism of electropolymerization of m-aminophenol (mAP) has been investigated in acetonitrile (AN) and methanol (MeOH) media. The rate of polymerization is found to be proportional to [mAP] (current)^0.5 at moderate current densities; at higher current densities, the rate of polymerization is independent of current density. A suitable mechanism has been proposed and the rate equation is derived to explain the observed factors. Rotating disc voltametry revealed that at low current densities, the rate of polymerization is charge controlled, while at high current densities it is diffusion controlled. The physicochemical characteristics of AN make it a better solvent than MeOH. © 1993 John Wiley & Sons, Inc.     

Direct determination of uranium in seawater by laser fluorimetry

A method for estimation of uranium in seawater by using steady state laser flourimetry is described. Uranium present in seawater, in concentration of approximately 3 ng ml⁻¹ was estimated without prior separation of matrix. Quenching effect of major ions (Cl⁻, Na⁺, SO₄⁻, Mg⁺, Ca⁺, K⁺, HCO₃⁻, Br⁻) present in seawater on fluorescence intensity of uranium was studied. The concentration of phosphoric acid required for maximum enhancement of fluorescence intensity was optimized and was found to be 5%. Similarly the volume of concentrated nitric acid required to eliminate the quenching effect of chloride and bromide completely from 5 ml of seawater were optimized and was found to be 3 ml. A simple equation was derived using steady state fluorescence correction method and was used for calculation of uranium concentration in seawater samples. The method has a precesion of 1% (1 s, n = 3). The values obtained from laser fluorimetry were validated by analyzing the same samples by linear sweep adsorptive stripping voltametry (LSASV) of the uranium-chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) complex. Both the values are well in agreement.     

Electrical conductivity of heat treated polyacrylonitrile and its copper halide complexes

The electrical conductivity of polyacrylonitrile homopolymer and polymer complexes of acrylonitrile (PAN) with CuCl₂, CuBr₂, and Cul₂ was measured at different temperatures. It was found that the electrical conductivity increased with temperature. Cyclic voltammetry was used for measuring the shift of the reduction peaks upon heat treatment of the polymer complexes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3057–3062, 1999     

Voltammetric quantification and speciation of mercury compounds

The use of a carbon paste electrode modified with a thiolic resin for the determination of inorganic mercury and organomercury compounds, present simultaneously in a sample, is described. The compounds are first preconcentrated at the electrode surface by means of a purely chemical reaction with the modifier on the electrode surface. The high affinity of the modifier for the mercury compounds ensures low limits of detection and determination. Differentiation between several mercury species is possible by control of the reduction potential applied to the working electrode. This selective reduction results in the formation of atomic mercury at the electrode surface which can be determined with a very high sensitivity by means of its re-oxidation wave in cyclic voltammetry. Optimization of the instrumental parameters and evidence for the reduction processes are discussed. Analysis of inorganic mercury in the presence of methylmercury, with a detection limit of 4 μg Hg 1⁻¹, and of methylmercury in the presence of inorganic mercury, with a detection limit of 2 μg Hg 1⁻¹, is described in detail. In both cases the preconcentration time is 6 min. Other organomercury species can also be quantified. Application of the method to environmental aquatic samples is discussed.     

Reduction of Triple-Charged Chromium Ions on Indium Cathode in Alkaline Sulfate Solutions

The problem of how the surface coverage of an indium electrode with chromium adatoms formed during the discharge of Cr(III) ions affects electrolytic evolution of hydrogen in alkaline solutions is studied using linear and cyclic voltametry. The method used permits stating that, in alkalinized media, the chromium deposition abruptly decelerates due to the formation of a hydroxide film on the electrode surface. Based on the results obtained, it is assumed that this film consists of mixed Cr(III)- and Cr(II)-containing hydroxo compounds (of the chromite type) and coadsorbed Cr_n clusters formed in the course of electrolysis.