Studies on the liquid-liquid extraction and ion and precipitate flotation of Co(II) with decanoic acid

The liquid-liquid extraction, ion and precipitate flotation of Co(II) from chloride media of 1·10^–4M initial Co(II) concentration and =0.1 have been investigated using decanoic acid and the results are compared. Organic solvents used were chloroform in the case of liquid-liquid extraction and ethanol (used as a solvent for the collector and a frother) in the case of flotation. From the results it appears that liquid-liquid extraction takes place through the formation of the complex: (CoR₂)₂(HR)₂ but flotation occurs through the formation of a surface active product which has the empirical formula CoR₂. The effects of pH and of decanoic acid concentration on the three separation processes were also investigated and the results discussed. Good agreement was observed between the experimental precipitate flotation curves and the theoretical curve calculated from the data published for Co(II) hydrolysis.     

Selenomethionine contents of NIST wheat reference materials

Values of the total selenium and selenomethionine (Semet) content of four wheat-based reference materials have been obtained by gas chromatography-stable isotope dilution mass spectrometry methods. The total Se method is an established one, and the results obtained with it are consistent with previously-assigned values. The Semet method (previously reported by our laboratory) is based on reaction with CNBr. Our data indicate that the four wheat samples (wheat gluten, durum wheat, hard red spring wheat, and soft winter wheat), though having a 30-fold range in total Se content, all have about 45% of their total Se values in the form of selenomethionine. Investigation of the CNBr-based method suggests that additional experiments are needed to verify that all selenomethionine in the wheat samples is accounted for, but also indicates that the values obtained are within 15% of the true values. As the form in which Se occurs in foods and dietary supplements is important from a nutritional perspective, adding information about Se speciation to total Se values in appropriate reference materials makes these materials more valuable in relevant analytical work.     

Effect of Ba and Bi doping on the synthesis and sintering of Ge-based apatite phases

Recently, high oxide ion conduction has been observed in the apatite-type systems La_9.33+x(Si/Ge)₆O_26+x/2, with conductivities approaching and even exceeding that of yttria-stabilized zirconia. The Ge-based phases have been reported to suffer from Ge loss and undergo irreversible structural changes on sintering at the high temperatures required to obtain dense pellets. In this paper we discuss doping studies (Ba, Bi for La) aimed at stabilizing the hexagonal apatite lattice to high temperature, and/or lowering the synthesis and sintering temperatures. The results show that doping with Ba helps to stabilize the hexagonal lattice at high temperatures, although Ge loss appears to still be a problem. Conductivity data show that, as previously reported for the Si-based systems, non-stoichiometry in the form of cation vacancies and/or oxygen excess is required to achieve high oxide ion conduction in these Ge-based systems. Neutron diffraction structural data for the fully stoichiometric phase La₈Ba₂Ge₆O₂₆ shows that the channel oxygen atoms show little anisotropy in their thermal displacement parameters, consistent with the low oxide ion conductivity of this phase. Bi doping is shown to lower the synthesis and sintering temperatures, although the presence of Bi means that these samples are not stable at high temperatures under reducing conditions.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, April 10–12, 2003     

QSPR Modeling of the Reactivity Parameters of Monomers in Radical Copolymerizations

For a series of monomers, QSPR test analysis is performed by optimizing the correlation weights of the local invariants of molecular graphs representing monomer structures in order to construct models of the reactivity parameters of monomers Q and e. This approach may be used as a tool in reactivity predictions for monomers for which no experimental data on Q and e are available.Original Russian Text Copyright © 2004 by A. A. Toropov, V. O. Kudyshkin, N. L. Voropaeva, I. N. Ruban, and S. Sh. Rashidova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 994–998, November–December, 2004.     

Determination of the thiol redox state of organisms: new oxidative stress indicators

This study describes a new methodology by which the concentrations of non-protein (NP) thiols glutathione (GSH), cysteine (CSH), N-acetylcysteine (AcCSH), and protein (P) thiols (PSH), as well as the contribution of these components to symmetric and mixed disulfides (NPSSR, NPSSC, NPSSCAc, PSSR, PSSC, PSSCAc, PSSP) can reliably be measured. The methodology consists of a strict sequence of methods which are applied to every sample. Free thiols at any given state of the procedure are measured by Ellmans assay, the CSH fraction is measured by its unique response in the ninhydrin assay, AcCSH is selectively measured with ninhydrin after enzymatic deacylation, proteins are separated from non-protein thiols/disulfides by precipitation with trichloroacetic or perchloric acid, disulfides are reduced into free thiols with borohydride, mixed disulfides between a protein and a non-protein component are measured by extracting the non-protein thiol from the protein pellet after borohydride treatment, and protein thiols/disulfides are measured after resolubilization of the protein pellet.When this method was applied to animal and fungal tissue, new molecular indicators of the thiol redox state of living cells were identified. The findings of the present study clearly show that the new parameters are very sensitive indicators of redox state, while at the same time the traditional parameters GSH and GSSG often remain constant even upon dramatic changes in the overall redox state of biological tissue. Therefore, unbiased assessment of the redox state also requires explicit measurement of its most sensitive thiol indicators.Electronic Supplementary Material Supplementary material is available in the online version of this article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

Synthetic diamond electrodes: Photoelectrochemical behavior of vacuum-annealed undoped polycrystalline diamond films

The photocurrent and photopotential for undoped polycrystalline diamond film electrodes prepared by chemical vapor deposition and annealed in vacuum at 1500–1640°C are measured. The metal-like samples (annealed at 1630°C) have a negligible photosensitivity. Judging from the positive sign of the photopotential and the cathodic direction of the photocurrent, the material under study formally behaves as a p-type semiconductor. The photoeffects are presumably caused by structure defects, in particular, the dislocations in diamond crystallites formed close to intercrystalline boundaries during the high-temperature annealing.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 343–349.Original Russian Text Copyright © 2005 by Pleskov, Krotova, Ralchenko, Khomich, Khmelnitskii.     

Study on analysis of153Sm-EDTMP stability in vitro and vivo by HPLC

The behavior of¹⁵³Sm-EDTMP in vitro and vivo is analyzed by the size exclusion HPLC. The experimental results show that EDTMP amounts have an obvious effect on the stability in vitro and uptake of¹⁵³Sm-EDTMP in the liver. HPLC analysis of urine sample indicates that¹⁵³Sm-EDTMP es excreted in the original form. The behavior in vivo of¹⁵³Sm-EDTMP containing 4 μg is similar to that of¹⁵³Sm-EDTMP containing 50 μg EDTMP at 1 h post-injection.     

Enzymatic kinetic of cellulose hydrolysis

The ethanol effect on the Trichoderma reesei cellulases was studied to quantify and clarify this inhibition type. To determine inhibition parameters of crude cellulase and purified exoglucanase Cel7A, integrated Michaelis-Menten equations were used assuming the presence of two inhibitors: cellobiose as the reaction product and ethanol as a possible bioproduct of cellulose fermentation. It was found that hydrolysis of cellulose by crude enzyme follows a model that considers noncompetitive inhibition by ethanol, whereas Cel7A is very slightly competitively inhibited. Crude cellulase is much more inhibited (K _iul=K _icl=151.9 mM) than exoglucanase Cel7A (K _icl=1.6 × 10¹⁵ mM). Also, calculated inhibition constants showed that cellobiose inhibition is more potent than ethanol inhibition both for the crude enzyme as well as exoglucanase Cel7A.