Calorimetric determination of solubility of water in pectin and physical state diagram of a pectin-water system

For the mixtures of pectin of different esterification degrees and water, heat capacities in the range of 80–320 K have been measured, and DTA measurements have been carried out in the range 80–450 K. The effect of water on the physical transitions of pectin has been studied, and the solubility of water in pectins of different esterification degrees at the temperature of melting of a liquid component has been determined. On the basis on the experimental data, the physical state diagram of the pectin-water system has been constructed and analyzed for the whole range of component concentrations within a wide temperature interval.     

Comparison of analytical techniques to quantify malondialdehyde in milk powders

Several analytical methods were compared to quantify malondialdehyde (MDA) in milk powders. Modified thiobarbituric acid (TBA) methods, using either visible spectrophotometry (direct absorbance reading or after third derivative transformation of the spectrum) or HPLC, required derivatisation at elevated temperature, which appeared to catalyse artefactual MDA formation and thus overestimate the MDA content. In contrast to the TBA derivatisation method, the measurement of MDA as the dinitrophenylhydrazone derivative by HPLC or as the phenylhydrazone product by GC-MS with a deuterated internal standard resulted in lower estimates in the ranges of 2-17- and 3-30-fold, respectively; apparently due to the milder derivatisation conditions. The estimates of MDA determined by both HPLC-UV and GC-MS techniques result in lower values which are similar in magnitude even though the GC-MS technique is more sensitive.     

Sorption of Uranium from Sulfuric Acid Leaching Solutions by Strongly Basic Anion Exchangers

The equilibrium and kinetic characteristics of uranium sorption from simulated sulfuric acid leaching solutions by AMP, Lewatit K 6367, Purolite A 500, Purolite A 600, and AM-p gel-like and porous strongly basic anion exchangers were studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 736–740.Original Russian Text Copyright © 2005 by Kolomiets, Troshkina, Sheremet’ev, Konopleva.     

Tribological properties of polytetrafluoroethylene modified with fullerene black in dry sliding friction

The effect of fullerene black introduced (after extraction of light fullerenes from the black with toluene) into polytetrafluoroethylene F-4 on its wear resistance and antifriction properties in sliding over steel at contact pressures in the range 0.2–2.0 MPa was studied.     

Reaction of 1,1,3,3-tetramethyldisiloxane with p-substituted acetophenones in the presence of platinum and rhodium complexes

Hydrosilylation of p-substituted acetophenones XC₆H₄COCH₃ (X = H, Me, MeO, HO, F, Cl, NO₂) with 1,1,3,3-tetramethyldisiloxane in the presence of rhodium and platinum complexes was studied. The Pt(II) complexes are less active but more selective catalysts of hydrosilylation of acetophenones. Six new 1-(1-arylethoxy)-1,1,3,3-tetramethyldisiloxanes were prepared.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1804–1811.Original Russian Text Copyright © 2004 by Zuev, de Vekki, Kuchaev, Vorobev, Skvortsov.This revised version was published online in April 2005 with a corrected cover date.     

Umbellactal, a novel diterpenoid from the Formosan soft coral Xenia umbellata

Umbellactal, isolated from the soft coral Xenia umbellata, is an unprecedented diterpenoid. The structure of umbellactal was established by extensive analysis of spectroscopic data.     

Analysis of 19-norandrosterone in human urine by gas chromatography–isotope-dilution mass spectrometry: method adopted by LGC for participation in the Comité Consultatif pour la Quantité de Matière (CCQM) Pilot Study P68

The method used at LGC for analysis of “total” 19-norandrosterone (19-norandrosterone glucuronide plus “free” 19-norandrosterone) in urine for the Comité Consultatif pour la Quantité de Matière Pilot Study (CCQM-P68) is described. The analytical method used was a modified version of the method developed at the National Measurement Institute of Australia, which used a hydrolysis and derivatisation procedure first described by the German Sports University. This method is routinely used by World Anti-Doping Agency-accredited laboratories for sports drug testing. The main modifications made to the method were the use of 19-norandrosterone glucuronide as a calibration standard and 19-norandrosterone glucuronide-d4 as an isotopically labelled internal standard, and the use of a bench-top quadrupole gas chromatograph–mass spectrometer. The results produced by LGC (2.14 ± 0.15 ng g⁻¹ expanded uncertainty, coverage factor k = 2) were in excellent agreement with those from other participating national metrology institutes and thus further validates the exact-matching isotope-dilution mass spectrometric procedures used at LGC for a wide range of reference measurement applications, including measurement of ng g⁻¹ levels of steroids in a biological matrix.     

Viscous flow of aqueous solutions of copper sulfate in the temperature range 20–50°C

Apparent molar volume, enthalpy of activation, and Gibbs energy of viscous flow of aqueous copper sulfate solutions were calculated from experimental data. The concentration dependences of the above parameters were analyzed from the standpoint of structural transformations. Original Russian Text V.N. Tseluikin, N.D. Solov’eva, O.G. Nevernaya, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 10, pp. 1747–1749.     

The unusual cyclic products from tetra- and penta-peptides of α-methylalanine

Tetra- and pentapeptides of α-methylalanine give with PCl₅, SOCl₂ etc. intermediates which, with or without loss of amino adds, lead to bi- and tricyclic products containing imidazole and piperazine rings through different routes.     

4-(<Emphasis Type="Italic">N,N</Emphasis>-Dialkylthiocarbamoylthio)-5-nitropyrimidines as new potential nitric oxide donors

On heating at pH 6.86, 4-(N,N-dialkylthiocarbamoylthio)-5-nitropyrimidines are transformed into dithiolopyrimidines, which are either oxidized to bis(4-dialkylthiocarbamoylpyrimidin-5-yl) disulfides or converted into 4,6-diamino-5-nitropyrimidine derivatives with carbon disulfide elimination. The direction of the reaction is determined by the nature of a substituent in position 2 of pyrimidine and the bulk of the thiocarbamate substituent. Mechanistic schemes for these processes were proposed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2777–2783, December, 2005.