Simultaneous Determination of Platinum and Palladium by Second Derivative Spectrophotometry Using 3-(2'-Thiazolylazo)-2, 6-Diaminopyridine as Chromophore Ligand

ABSTRACT

A second derivative spectrophotometric method has been developed for the determination of palladium and platinum in mixtures. The method is based on the formation of the platinum and palladium complexes with 3-(2-thiazolylazo)-2, 6-diaminopyridine, (2, 6-TADAP), in the presence of 1.7 M perchloric acid solution, upon heating at 90° C for 30 min and on the subsequent direct derivative spectrophotometric measurement. The zero-crossing approach and the graphic method were used for determination of platinum and palladium, respectively. Each analyte was determinated in the presence of one another in the ranges 8.9×10^-7 -3.1×10^-5 M for platinum and 4.6×10^-7 - 6.8×10^-5 M, for palladium. The detection limits achieved (3a) were found to be 2.7×10^-7 M of platinum and 1.4×10^-7 M of palladium. The relative standard deviations were in all instances less than 1.0%. In this work is included a study of effect of interferents and the application of the proposed method in synthetic mixtures.     

衍生气相色谱-质谱法测定水中氯代酸性除草剂

采用H2SO4加入法改变了酸性除草剂在水中的存在状态,对碱性活化点的存在与消除进行了分析,同时对不同试剂的萃取效率进行了对比,建立了衍生气相色谱-质谱法测定水中10种氯代酸性除草剂的方法。化合物检出限均低于10.0 ng/L,回收率范围为60%～120%。     

A new Cu(II)-5-(4-sulphophenylazo)-8-aminoquinoline complex used for copper determination in presence of gold and silver in water and mineral samples

In this work, a characterization of reagent chromophere 5-(4-sulphophenylazo)-8-aminoquinoline [SPA] by IR and ¹H RMN was carried out and a pK_a value of 3.55 ± 0.03 was found as well. An 1:2 stoichiometry for the Cu(II)-SPA complex was determined at pH 9 by Job and molar ratio methods. A value of 1.4 × 10¹⁴ for the stability constant was also found. Based on the formation of this complex a new method for the copper determination in presence of gold and silver was developed by derivative spectrophotometry using a previous preconcentration on solid phase. In this method, the analytical measures were executed directly in the solid phase containing the complex. The Cu(II) reacts with the reagent chromophere SPA previously retained in the anionic exchange DEAE Sephadex A25. In this determination, the first derivative at 605 nm was used. The quantification range was between (3.2 ± 0.3 × 10⁻¹) × 10⁻⁸ and (94.4 ± 0.9) × 10⁻⁸ mol L⁻¹ (3.2 ± 0.3 × 10⁻¹) × 10⁻⁸ , and (94.4 ± 0.9) × 10⁻⁸ mol L⁻¹. The repeatability expressed as RSD was between 1.1 and 2.0%. The method was applied successfully for the copper determination in mineral residuals and natural water samples. The results were consistent with those provided by ICP-mass spectrometry.     

Thermodynamic derivative properties and densities for hyperbaric gas condensates: SRK equation of state predictions versus Monte Carlo data

The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, a_ij, and three expressions of the crossed terms of the repulsive parameter, b_ij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of a_ij and b_ij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations.     

Effects of diclofenac on EPC liposome membrane properties

In this work the interaction of a non-steroidal anti-inflammatory drug (NSAID), diclofenac, with egg yolk phosphatidylcoline (EPC) liposomes, used as cell-membrane models, was quantified by determination of the partition coefficient. The liposome/aqueous phase partition coefficient was determined by derivative spectrophotometry, fluorescence quenching, and measurement of zeta-potential. Theoretical models based on simple partition of the diclofenac between two different media, were used to fit the experimental data, enabling the determination of K_p. The three techniques used yielded similar results. The effects of the interaction on the membranes characteristics were further evaluated, either by studying membrane potential changes or by effects on membrane fluidity. The liposome membrane potential and the size and size-homogeneity of liposomes were measured by light scattering. The effects of diclofenac on the internal viscosity or fluidity of the membrane were determined by use of spectroscopic probes—a series of n-(9-anthroyloxy) fatty acids in which the carboxyl terminal group is located at the interfacial region of the membrane and the fluorescent anthracene group is attached at different positions along the fatty acid chain. The location of the diclofenac on the membrane was also evaluated, by fluorescence quenching using the same series of fluorescent probes. Because the fluorescent anthracene group is attached at different positions along the fatty acid chain, it is possible to label at a graded series of depths in the bilayer. The interactions between the drug and the probe are a means of predicting the location of the drug on the membrane.     

氢化松香及其衍生物的制备研究进展

氢化松香是重要的天然可再生资源松香的深加工产品之一,在电子、食品、医药等领域有着重要的用途。本文介绍了氢化松香的主要组分、氢化松香国内外工业化生产历程及氢化松香制备工艺,特别是由贵金属钯和非贵金属镍为催化剂的制备工艺的研究现状;对近年来氢化松香和二氢枞酸衍生物,主要是以氢化松香为整体的衍生物的制备研究进行了综述,并对氢化松香及其衍生物研究前景进行了展望。     

交流示波极谱法中if～E曲线的研究（Ⅱ）：if～E曲线的理论公式

提出利用i_f～E曲线代替常用的dE/dt～E曲线的新的交流示波极谱法,并研究了该法的基本理论,推导出i_f～E曲线的理论公式。     

柱前衍生-气相色谱-电子捕获法同时检测水体中的9种全氟羧酸

建立了柱前衍生-气相色谱-电子捕获(GC-ECD)法同时测定水中PFBA、PFPeA、PFHxA、PFHpA,PFOA,PFNA,PFDA,PFUnA及PFDoA等(全称见正文)9种全氟羧酸(Perfluorinated carboxylic acids,PFCAs).使用2,4-二氟苯胺(2,4-Difluoroaniline,2,4-DFA)为衍生剂,N,N'-二环己基碳二亚胺(N,N'-Dicy-clohexylcarbodiimide,DCC)为脱水剂,与PFCAs形成酰胺衍生产物,衍生产物通过TR-5毛细管色谱柱分离,并以ECD检测器进行检测.对全氟羧酸衍生化过程中2,4-DFA和DCC用量、衍生反应溶剂、反应温度、反应时间等条件进行了优化,得出最佳衍生化条件.结果表明,在最优实验条件下,9种PFCAs衍生产物的线性相关系数＞0.99,检出限为0.62～ 1.38 μg/L,相对标准偏差RSD为1.3％～7.5％.应用本方法对城市污水中全氟类羧酸进行了分析,城市污水中存在以PFPeA、PFHpA和PFOA为主的痕量PFCAs化合物,实际样品的加标回收率在84.4％ ～ 120.9％之间.本方法稳定、可靠、成本低,能够满足水样中多种全氟羧酸的同时检测的要求,可为水体中全氟化合物的污染评价提供技术支持.