Relationship between the density of supercritical CO<Subscript>2</Subscript> + ethanol binary system and its critical properties

The dependent relation between temperature and pressure of supercritical CO₂+ ethanol binary system under the pressure range from 5 to 10 MPa with the variety of densities and mole fractions of ethanol that range from 0 to 2% was investigated by the static visual method in a constant volume. The critical temperature and pressure were experimentally determined simultaneously. The PTρ figures at different ethanol contents were described based on the determined pressure and temperature data, from which pressure of supercritical CO₂ + ethanol binary system was found to increase linearly with the increasing temperature. P-T lines show certain convergent feature in a specific concentration of ethanol and the convergent points shift to the region of higher temperature and pressure with the increasing ethanol compositions. Furthermore, the effect of density and ethanol concentration on the critical point of CO₂ + ethanol binary system was discussed in details. Critical points increase linearly with the increasing mole fraction of ethanol in specific density and critical points change at different densities. The critical compressibility factors Z_c of supercritical CO₂ + ethanol binary systems at different compositions of ethanol were calculated and Z _c -ρ figure was obtained accordingly. It was found from Z _c -ρ figure that critical compressibility factors of supercritical CO₂ unitary or binary systems decline linearly with the increasing density, by which the critical point can be predicted precisely.     

Photochemical thallimetric oxidations-estimation of formic acid

A simple, rapid and convenient redox method has been developed for the estimation of formic acid. Formic acid is photochemically oxidized with thallium(III) in the presence of bromide as catalyst, and the thallium(I) formed is determined by titration with potassium bromate. The procedure can also be used for the estimation of thallium(III) with formic acid as reductant.     

Alternative mobile phases for the reversed-phase high-performance liquid chromatography of peptides and proteins

The use of a high content of acetic acid as mobile phase additive for the reversed-phase high-performance liquid chromatography (RP-HPLC) of several proteins and extracts of biological tissues was evaluated for a divinylbenzene (DVB)-based stationary phase, and the separations obtained with acetic acid gradients in acetonitrile, isopropanol or water were compared with classical polypeptide RP-HPLC on silica C4 with trifluoroacetic acid (TFA)-acetonitrile. The separation patterns for recombinant derived interleukin-1 beta (IL-1 beta) on the C4 column eluted with TFA-acetonitrile and the DVB column eluted with acetic acid-acetonitrile were similar, but only the polymeric column was able to separate the components present in an iodinated IL-1 beta preparation. Neither eluent had any harmful effect on the biological activity of IL-1 beta isolated after RP-HPLC. Several standard proteins could be separated when the polymeric column was eluted with acetic acid gradients in acetonitrile, isopropanol or water and, although the separation efficiency with acetic acid in water was lower than that in combination with classical organic modifiers, insulin, glucagon and human growth hormone (hGH) were eluted as sharp, symmetrical peaks. The recoveries of insulin and hGH were comparable for all three mobile phases (80-90%). The separation patterns obtained from a crude acetic acid extract of a normal and a diabetic, human pancreas analysed using acetic acid gradients with or without organic modifiers were found to be similar and comparable to those obtained on a silica C4 column eluted with an acetonitrile gradient in TFA. The principal differences resulted from the use of different UV wavelengths (215 nm for TFA-acetonitrile, 280 nm for acetic acid). Acetic acid extracts of recombinant derived hGH-producing Escherichia coli were separated on the DVB column eluted with an acetic acid gradient in water. Although the starting material was a highly complex mixture, the hGH isolated after this single-step purification was surprisingly pure (as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis). Consequently several (pure) polypeptides and complex biological samples were separated on a polymeric stationary phase eluted with acetic acid gradients in water without the use of organic modifiers.     

Synthesis, Structure, and Antimicrobial Activity of Complexes of Pt(II), Pd(II), and Ni(II) with the Condensation Product of 2-(Diphenylphosphino)benzaldehyde and Semioxamazide

Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation.     

Volumetric Properties of the Ternary System 1,4-Dioxane + Butyl Acrylate + Ethyl Acrylate and Its Binary Butyl Acrylate + Ethyl Acrylate at 298.15 K

Densities of the ternary system 1,4-dioxane + butyl acrylate + ethyl acrylate and its binary butyl acrylate + ethyl acrylate have been measured in the whole composition range, at 298.15 K and atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter. The calculated excess molar volumes of the binary system are positive and were correlated with the Redlich–Kister equation and with a series of Legendre polynomials. Several models were used to correlate the ternary behavior from the excess molar volume data of their constituent binaries and were found equally good to fit the data. The best fit was based on a direct approach, without information on the component binary systems.     

Photochemical reactions of W(CO)6 with hydrosilanes: synthesis, spectroscopic characteristic, and crystal structure of W(CO)3(η-PhSiHPh2)

Photolysis of W(CO)₆ in the presence of Ph₃SiH in n-heptane leads to the formation of the first tricarbonyl(η⁶-triphenylhydrosilane)tungsten complex W(CO)₃(η⁶-PhSiHPh₂) (1) in good yield (ca. 70%). The molecular structure of the new tungsten-silane compound was established by single-crystal X-ray diffraction studies and characterized by IR, UV-Vis, ¹H, ¹³C{¹H}, and ²⁹Si{¹H} NMR spectroscopy.     

Dynamic light scattering and cryogenic transmission electron microscopy investigations on metallo-supramolecular aqueous micelles: evidence of secondary aggregation

Metallo-supramolecular diblock copolymers consisting of a polystyrene (PS) block connected to a poly(ethylene oxide) (PEO) block by a bis(terpyridine)ruthenium complex (PS₂₀-[Ru]-PEO _y ) were used to prepare aqueous micelles. The length of the PS block was kept constant, while two PEOs of different molecular weight were used. The resulting hydrated micelles and aggregates were characterized by a combination of cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering measurements. The results were compared to those obtained for a covalent counterpart (PS₂₂-b-PEO₇₀). Cryogenic transmission electron microscopy allowed visualization of the PS core of the micelles. Moreover, the aggregates result from clustering of individual micelles.     

Sampling procedure and a radio-indicator study of mercury determination in whole blood by using an AMA 254 atomic absorption spectrometer

A sampling procedure appropriate for the determination of mercury in whole blood was tested by using both inactive controls and a ¹⁹⁷Hg mercury radio-indicator. To exclude the influence of the instrumental device (an AMA 254 single-purpose mercury atomic absorption spectrometer) on the determination of mercury in whole blood, the function of the instrument was checked by using rat blood with metabolised ¹⁹⁷Hg. The measurement procedure was found to be free of errors. However, the study showed that the material used for the sampling vessels is a crucial parameter for obtaining accurate analytical results. The stability of solutions and samples was tested towards polyethylene (PE) and polypropylene (PP) vessels. PE displayed a time-dependent increase in the mercury content both in the samples and in the blood control material. The probable cause of this increase was direct contamination from the material of the vessel and/or diffusion of mercury from the environment through the vessel walls related to a strong complexing affinity of the sample matrix. This assumption was confirmed by supplying the vessels with the complexing agent Na₂EDTA (0.05 mol L^–1). Commercial PP vessels for blood sampling (Sarstedt S-Monovette Metall Analytik) did not give rise to statistically significant variations in mercury content in the samples and blood control material over a 30-day period.     

Transition metal coordination polymers with polycarboxylic acid as bridging ligands: Synthesis and structure characterization of [Fe(μ4-bta)0.5(phen)(OH)]<Subscript>n</Subscript>

A new 2D (two-dimensional) coordination polymer, [Fe(μ4-bta)o.5(phen)(OH)]_n (1), has been hydrothermally synthesized with FeCl₃ 6H₂, Na₄bta (h₄bta = 1,2,4,5-benzentetracarboxylic acid), 1,10-phen (1,10-phenanthroline) and H₂O as raw materials. The crystals of the compound belong to monoclinic P2₁/n space group, a = 1.0129(2) nm, b = 0.9265(2) nm, c = 1.5696(3) nm, β=91.37(3)°V=1.4721(5) nm³,Z=3, final R₁=0.0292, wR ₂=0.0798 for 2572 [/>2σ(/)] observed reflections. The result of structure determination shows that in the compound each bta ligand is connected with four Fe³, forming a new μ4-coordination mode. Four deprotonated carboxylic groups of bta link to Fe³ ions alternatively through monodentate and bidentate coordination fashion, constructing 2D layer network. The measurement of variable temperature magnetic susceptibility indicates that there exist antiferromagnetic interactions between Fe³ ions in the compound. The TGA spectrum displays relatively fine thermal stability of the compound. In addition, IR and UV-Vis spectra of compound 1 have also been measured.     

Solid-state pH nanoelectrode based on polyaniline thin film electrodeposited onto ion-beam etched carbon fiber

An ultramicro pH sensor has been constructed based on a thin polyaniline film that was electrochemically deposited onto a carbon fiber nanometer-size electrode. The substrate nanoelectrodes were fabricated using ion-beam conically etched carbon fibers with tip diameters ranging ca. from 100 to 500 nm. The polyaniline film was deposited from HCl solution containing the aniline monomer by cycling the potential between −0.2 and +1.0 V. The electromotive force (emf) signal between the pH sensitive polyaniline-coated nanoelectrode and an Ag/AgCl reference electrode was linear over the pH range of 2.0-12.5 with a slightly super-Nernstian slope of ca. −60 mV/pH unit. Response times ranged from several sec at pHs around 7 up to 2 min at pH 12.5. The proposed pH nanoelectrode displayed high ion selectivity with respect to K⁺, Na⁺, Ca²⁺, and Li⁺, with log K_H,M values around −12 and has a working lifetime of about 20 days. Key parameters important for the pH nanoelectrode performance, including polyaniline film preparation, selectivity, response time, temperature dependence, relative coating thickness, stability, and reproducibility, have been characterized and optimized. The performance of the pH nanoelectrode was examined by measuring the pH of several real samples including body fluids (serum, urine) and low ionic strength water samples (rain, deionized and tap water). The results agreed very well with those obtained by using commercial glass pH electrodes. The proposed pH nanoelectrode demonstrated attractive properties and seems particularly promising for use under physiological conditions.