Effect of solvents having different dielectric constants on reactivity: A conceptual DFT approach

Conceptual density functional theory is exploited to understand the reactivity in a medium of solvents with increasing dielectric constants. Aprotic as well as protic solvents are used for this study. It is found that the global parameters, such as chemical potential and hardness, decrease from gas phase to solvent phase with increasing dielectric constant. However, it is observed that the Fukui functions of the reactive atoms increase significantly with the dielectric constants of the aprotic solvents while for the protic solvents the variation of the reactivity indices is insignificant. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Fluorine ion selective electrode for microdetermination of fluorine in organic compounds

A simple procedure is described for the decomposition of organic fluoro-compounds by a quartz oxygen flask, with auxiliary combustible adhesive paper and in combination with the fluorine ion selective electrode's new measuring technique. Polymers of high F content, fluorocarbons, and compounds of the ---CF₃ functional group can be quantitatively decomposed. The presence of N, Cl, Br, I, S, P, As, B, Si, K, Na, Hg, Mg, Al, Fe, Pb, Ag, Cu, and Zn do not interfere with the quantitative microdetermination of organic fluorine element. The absolute error is ±0.30%.     

Determination of stability constants of copper(II) complex of glycine in water + alcohol mixed solvents with ion selective electrode technique

The first stability constants (log beta(1)) of the copper(II) complex of glycine in water and in 13 water + alcohol (isopropanol, tert-butanol, 1,2-propylene glycol and glycerol) solvents have been determined at 25 degrees C and an ionic strength of 0.10, from pH and pCu measurements of cells containing copper(II) ion selective electrode. It has been shown that as the proportion of the alcohol increases, the stability constants become increasing positive in all of the mixed solvents examined. An almost linear relation between log beta(1) and the mole fraction of alcohol was found for the complex in aqueous solutions of isopropanol, tert-butanol and glycerol. The response of the copper(II) ion selective electrode in water and in water + alcohol mixed solvents was also investigated. The advantages of using an ion selective electrode to determine the stability constants in mixed solvents are discussed.     

Calcium ion selective membrane electrode

The calcium salts of the mono- and diesters of [4-(1,1,3,3-tetramethylbutyl)phenyl phosphoric acid] have been prepared, and the individual esters as well as mixtures of the esters have been used with several varieties of polyvinyl chloride to construct macro membrane electrodes selective to calcium ions. These electrodes have been calibrated by using solutions of CaCl₂ and Ca ion buffers. The mixed ester electrodes showed Nernstian response in the concentration range 10^-1 to 10^-7M; the diester electrodes showed Nernstian response down to 7.9 x 10^-8M. The detection limit of the mixed ester electrode was 10^-8M, whereas that of the diester electrode was 7.9 x 10^-9M. Contrary to these results, the monoester electrodes showed unsatisfactory behavior. The responses of both the mixed ester and diester electrodes to calcium ions were not affected by the presence of sodium, potassium, or other divalent ions. Only ferric and lanthanum ions showed interferences with the electrode response to calcium ions. p]The electrode response was independent of pH in the approximate range 5–8 at a CaCl₂ concentration of 10^-4M. As the Ca ion concentration was increased, the range of pH independence widened to approximately 4–8. The dynamic response time constant of the mixed ester electrode was in the range 0.7–1.5 sec, whereas that of the diester electrode was in the range 0.5–0.75 sec.     

Preparation and application of selenite ion selective electrode

A new selenite ion selective electrode using 4,6-dibromopiaselenole as active material, PVC as membrane matrix and dibutyl phthalate as plasticizer has been developed. An analytically useful potential change occurs from about 10(-6)-10(-1)M Se(IV), and the slope of the linear portion is -23.6 mV/10-fold change in Se(IV) concentration at a temperature of 21 degrees . The electrode shows fairly good selectivity for selenite ion over other anions and has been used for the successful determination of total selenium in human hair.     

Effect of the nature of organic solvents on their interaction with metal halides

The radioactive tracer technique was used for studying the extraction and predicting the best conditions of separation of arsenic halides by organic solvents of different nature. Sulphuric acid was found to enhance the extraction of arsenic halides. Extraction of AsI₃ increases in the order cyclohexane <CCL₄ toluene <o-xylene <CHCl₄ and is quantitative by benzene and nitrobenzene. For a given extraction increases in the order AsCl₃<AsBr₃< <AsI₃. Spectral measurements were made on some solvents; at maximum absorption there was a linearity between absorbance and AsI₃ concentration up to 2·10⁻⁴ M for o-xylene and to 2.5·10⁻⁴ M for nitrobenzene.     

Effect of the nature of organic solvents on their interaction with metal halides

Journal of Radioanalytical and Nuclear Chemistry - A systematic study has been carried out on the extraction of thallium halides with aromatic hydrocarbons, TBP and Amberlite LA2. Extraction has...     

Spectral parameters and Hamaker constants of silicon hydride compounds and organic solvents

Cyclopentasilane (CPS) and polydihydrosilane, which consist of hydrogen and silicon only, are unique materials that can be used to produce intrinsic silicon film in a liquid process, such as spin coating or an ink-jet method. Wettability and solubility of general organic solvents including the above can be estimated by Hamaker constants, which are calculated according to the Lifshitz theory. In order to calculate a Hamaker constant by the simple spectral method (SSM), it is necessary to obtain absorption frequency and function of oscillator strength in the ultraviolet region. In this report, these physical quantities were obtained by means of an optical method. As a result of examination of the relation between molecular structures and ultraviolet absorption frequencies, which were obtained from various liquid materials, it was concluded that ultraviolet absorption frequencies became smaller as electrons were delocalized. In particular, the absorption frequencies were found to be very small for CPS and polydihydrosilane due to σ-conjugate of their electrons. The Hamaker constants of CPS and polydihydrosilane were successfully calculated based on the obtained absorption frequency and function of oscillator strength.     

茜素S选择电极的研制和应用

本文报道了茜素S电极的研制和应用。比较了季铵盐、季鏻盐、碱性染料和邻二氮菲金属配合盐作为活性物质、各种介体溶剂以及活性物质在膜相中的含量对电极性能的影响。以三辛基甲基氯化铵制成的PVC膜型电极对茜素S在2×10~(-4)～5×10~(-7)M浓度范围内呈Nernstian响应,检测下限为2×10~(-7)M。测定了一些阴离子的选择系数,ClO_4~-,CNS~-,I~-以及能与茜素S配合的金属离子有明显干扰。报道了以茜素S电极为指示电极,用EDTA和茜素S为滴定剂滴定钪和稀土的情况。以茜素8电位滴定钪及钴-钐合金中的钐,都获得良好的结果。     

A potentiometric enzyme electrode for monitoring in organic solvents

A potentiometric enzyme electrode is described for monitoring reactions in organic solvents. By use of an enzyme deposited on magnetic particles which are attracted to the tip of the electrode by means of a magnetic field, it is possible to produce an electrode in which the enzyme can easily be exchanged. As an example, studies of the chymotrypsin-catalyzed ester synthesis in diisopropyl ether and in toluene at varying water contents are reported. The results are consistent with those obtained from batch experiments. Operational behaviour and signal stability of the system makes this kind of potentiometric enzyme electrode attractive for monitoring bioorganic processes.     

溶胶-凝胶法修饰的硫氰酸根离子选择性电极(ISE)的研究

报道了一种基于溶胶-凝胶技术的新型硫氰酸根电极,讨论了电极性能的影响因素.该电极有良好的能斯特响应,斜率为63 mV/pC,线性范围为1.0×10-2～6.0×10-6mol/L,检出限为4.0×10-6 mol/L,适宜的pH范围为3.4～7.1.     

溶胶-凝胶膜修饰碳酸根离子选择电极的研究

利用溶胶-凝胶技术包埋电活性物质,制备溶胶-凝胶膜修饰的碳酸根离子选择电极。探索了Sol-Gel膜修饰CO32-选择电极的制备方法、测试条件及共存物的影响。电极的线性范围1.0×10-1~1.0×10-5mol/L,相关系数R2=0.993,检测限8.9×10-6mol/L,响应斜率22.1 mV/pCO3。电极稳定性和重现性良好,用于实际样品测定,回收率95.9%~99.0%。     

The effect of aqueous organic solvents on the dissociation constants and thermodynamic properties of alkanolamines

The dissociation constants of protonated monoethanolamine and N-methyldiethanolamine have been determined in methanol–water, ethanol–water, and t-butanol–water solvents. The alcohol mole fractions were ranging from 0.2 to 0.95 and the temperatures from 283 to 323 K, 283 to 333 K, and at 298.15 K, respective to the different solvents. The experimental results are reported with the standard state thermodynamic properties. The basic strength of the protonated alkanolamine decreases with decreasing dielectric constant and increasing temperature of the solvent.     

Conducting polymer ion sensor electrodes-III. Potentiometric sulfide ion selective electrode

A new potentiometric sensor electrode for sulfide based on conducting polymer films is introduced. The electrode is formed by electrochemically depositing a film of poly(3-methylthiophene) and poly(dibenzo-18-crown-6) onto an alloy substrate. Different methods were used for the electrode preparations. The alloy used has a low melting point, which allowed its use for manufacturing a microsize version of this electrode. The electrode response is stable for 3 days. The working temperature range for this electrode is between 10 and 40 degrees C. The linear dynamic range is 1.0x10(-7)-1.0x10(-2) M and measures total sulfide concentration over a range of pH from 1 to 13. The polymer electrode showed high selectivity for sulfide in the presence of many common interfering anions. The electrode is useful for the measurement of total sulfide in biological environments and can be manufactured in the micron scale. Therefore, it will be useful for the measurement within biofilms.     

The role of PVC in ion selective electrode membranes

The behaviour of a solution of NaBPh₄ in a PVC membrane plasticized by di-octyl sebacate is compared with a solution of NaBPh₄ in pure liquid di-octyl sebacate. In the liquid the NaBPh₄ is present as ion pairs with ~ 0.2% of these dissociated in a 1 mM solution. By contrast in the membrane 1 mM solution is 74% dissociated. This difference in behaviour arises chiefly from the higher dielectric constant of the membrane phase.     

New metal complex systems as electrode active components of ion selective electrode membranes

New donor-acceptor 3d-transition metal complexes were synthesized and the cobalt and nickel complexes were studied by X-ray diffraction; CIF files CCDC no. 1516693 (III(Ni)) and 1516694 (III(Co)). The crystal structure details of the reactants were discussed. The proposed compounds were tested as the active components of ion selective electrode membranes for determination of thiocyanate ions. The selectivity of the SCN-SE with metal complex-based membranes depends on the ligand structure and the central metal ion type. The proposed electrode is suitable for determination of thiocyanate ions in the presence of sulfate, chloride, nitrate, nitrite, bromide, and iodide ions.     

Coated wire thorium ion selective electrode: Part I

Coated wire ion selective electrode for thorium ion selective potentiometry was developed. Thorium ion selective coated wire electrodes were prepared by depositing a membrane comprising of Aliquat-336 loaded with Th(NO₃)₆²⁻ ions and poly vinyl chloride in varying proportion. A linear near-Nernstian response with a slope of −29.5 ± 0.3 mV over thorium concentration range of 1 × 10⁻¹–3 × 10⁻⁵ M in constant total nitrate concentration of 6 M was obtained for the electrodes of almost all the composition studied. In spite of small drift in response potential from composition to composition, day to day as well as from electrode to electrode, the slope of potential response line was constant within experimental error. Moreover, the electrode once prepared could be conveniently used over a period of one and half month.     

Coated wire thorium ion selective electrode: Part II

Thorium ion selective coated wire electrode (Th-ISE) developed in this laboratory was investigated for interference from most likely impurity ions like Fe(III), U(VI), Ca(II) and Mg(II) and corresponding selective coefficient were obtained. The Th-ISE electrode was also used for the end point detection of Th-EDTA titration for Th determination in the range of 3–6 mg and the accuracy and the precision of the results obtained was within ±0.5%.