Quantitative Determination of Cationic and Nonionic Surfactants in Aqueous Solutions of Their Mixtures by Capillary Zone Electrophoresis

A method based on capillary zone electrophoresis is developed for a quantitative determination of cationic (dodecylpyridinium bromide) and nonionic (Triton X-100) surfactants absorbing in the UV region. The effect of the pH and ionic strength of the solution on the output time and shape of the resultant peaks is studied, and the optimal conditions of the analysis are determined. For both surfactants, the analytical signal (the area of the peak on the electrophoregram) is found to linearly depend on the concentration. It is established that the presence of a second surface-active component does not affect the signal of the surfactant analyzed; thus, surfactants may be quantitatively determined in both individual and mixed solutions. The method of capillary zone electrophoresis is shown to be applicable for determining the CMCs of surfactants.     

AAS determination of trace elements in high-purity gold after matrix separation by solvent extraction

Summary A method is described for the determination of 20 trace elements in gold of a qualification of about 4–5 N. The matrix is separated by solvent extraction into methylethylketone/chloroform and the trace elements are determined in the aqueous phase by AAS (flame or graphite furnace). The procedure is optimized as to minimize the number of contamination sources.     

Kerr constants of some nitrogen-containing heterocycles

The molecular Kerr constants [ (mK₂)] were measured for pyridine, 2- and 4-methylpyridines, quinoline, and acridine in dioxane. The molecular moments of pyridine and 4-methylpyridine are directed along the axis of maximum polarizability. The B = B₁₂—B₁ values for dilute solutions of azaaromatic compounds in dioxane are proportional to T^–2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 974–976, July, 1971.     

Calcium- und Magnesiumtrennung von Mn, Fe, Al und Ti mit chelatbildendem Harz, Tri?thanolamin und Oxalat

Zusammenfassung Die verhältnismäßig schnell durchführbare Trennung des Calciums und Magnesiums von Mn, Fe, Al und Ti erfolgt durch deren selektive Sorption an dem Iminodiacetatgruppen enthaltenden Kationenaustauscher Dowex A-1 aus alkalischer Lösung, die Triäthanolamin und Citrat enthält. Es erwies sich, daß Mn(III), Fe(III) und Al bei pH>13±0,5 Komplexe bilden, die am Kationit nicht haftenbleiben. Titan verbleibt als Citratkomplex in Lösung. Magnesium wird mit alkoholischer Ammoniumoxalatlösung eluiert, Calcium mit 0,3 N HCl. Die Bestimmung von Ca, Mg und Mn erfolgt komplexometrisch.Entwickelt wurden zwei Varianten der Methode: für die Analyse von Eisenerzen, Manganerzen und Agglomeraten, sowie von Silicaten.

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Separation of calcium and magnesium and of both ions from Mn, Fe, Al and Ti using chelate resin, triethanolamine and oxalat

The method is based on the selective sorption of Ca²⁺ and Mg²⁺ on a cation-exchange resin with iminodiacetic groups from alkaline solution containing triethanolamine and alkali metal citrates. In solution with pH>13±0.5 Mn(III), Fe(III) and Al(III) form complexes with triethanolamine, which are not sorbed by the cation-exchange resin. Titanum(IV) forms citrate complexes and also remains in the solution. Magnesium is eluted with alcoholic solution of ammonium oxalate, calcium with 0.3 N hydrochloric acid. The determination of calcium and magnesium in the corresponding eluates as well as that of manganese in the solution is carried out complexometrically.Two variants of the method are described: for the analysis of iron ores, manganese ores, agglomerates and for silicates.

     

Synthesis and Physicochemical Properties of d- and f-Metal Complexes with Alloxan

Fifteen d- and f-metal complexes with alloxan were synthesized. Complexes of two types, in which alloxan exists in mono- or diinozed form, were found to be formed, depending on the synthesis conditions (solvents and pH of solutions). Physicochemical properties of alloxanates were studied by IR, X-ray photo electron, and electronic absorption spectroscopies. The alloxan molecule was calculated using the PPP method. The structures of complexes synthesized were suggested.     

Organic-inorganic hybrid materials based on N=C=O functionalised silan modified with titanium and zirconium

This work investigates the influence of the precursor trimethylsilil isocyanate on the sol-gel synthesis of hybrid materials. The obtained Si−O−C−N network is additionally modified by titanium and zirconium alcoxypropoxides in the range of 10 to 30 wt. %. The structure of the obtained hybrid materials before and after pyrolysis up to 1100°C was investigated by methods of XRD, FTIR and ²⁹Si MAS NMR. We established that the hybrid structure was stable up to 600°C based on IR study. The structural transformation of the hybrid materials into oxycarbonitrogen system started at 800°C. The network of the hybrids modified by titanium remained stable and amorphous up to the final temperature of the pyrolysis (1100°C) compared to the gels modified by more than 10 wt.% Zr. It was confirmed by XRD analysis that the last mentioned are nanocomposite materials, built from carbooxynitrogen vitreous matrix and ZrO₂-nanocrystals (tetragonal). The NMR method verified the presence of heterometallic bonds (Si−O−Ti and Si−O−Zr) and Q₄, ZrQ₃ or TiQ₃, NSiO₃ and D structural units in the gels.     

Flow injection on-line sorption preconcentration of platinum in a knotted reactor coupled with electrothermal atomic absorption spectrometry

A flow injection on-line sorption preconcentration method for the electrothermal AAS determination of platinum has been developed. The pyrrolidine dithiocarbamate complexes of either Pt⁴⁺ or Pt²⁺, formed in 0.7 mol L^–1 HNO₃, are on-line adsorbed on the inner walls of a PTFE knotted reactor and subsequently eluted with methanol. An enhancement factor of 112 and a detection limit (3 σ) of 10 ng L^–1 along with a sampling frequency of 21 h^–1 are achieved with a 90 s preconcentration time at a sample flow rate of 8.8 mL min^–1. The relative standard deviation is 2.5% for 0.4 μg L^–1 Pt. The method has been applied to the determination of platinum in blood samples. Received: 6 October 1997 / Revised: 26 November 1997 / Accepted: 3 December 1997     

Reactions of 2,3,5-trichloro-4,4-ethylenedioxy-2-cyclopentenone with some ambident nucleophiles. Sterically loaded functionalized 6-azabicyclo[3.1.0]hex-5-enes

2,3,5-Trichloro-4,4-ethylenedioxy-2-cyclopentenone reacted with sodium azide in tetrahydrofuran to give the expected 3-azido derivative which was converted into 1,3-dichloro-4,4-ethylenedioxy-6-azabicyclo-[3.1.0]hex-5-en-2-one and 3-amino-2,5-dichloro-4,4-ethylenedioxy-2-cyclopentenone on heating in chloroform. The reaction of 2,3,5-trichloro-4,4-ethylenedioxy-2-cyclopentenone with potassium thiocyanate, depending on the conditions, afforded the corresponding 3-thiocyanato derivative or symmetric sulfide. Treatment of the title compound with hydroxylamine resulted in opening of the dioxolane ring with simultaneous formation of oxime via replacement of chlorine at the neighboring sp ²-carbon atom.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1569–1573.Original Russian Text Copyright © 2004 by Shavaleeva, Ivanova, Usmanova, Akhmetvaleev, Miftakhov.     

The Role of Surfactants in the Formation of Highly Dispersed Iron–Zirconium Oxide Composites with Uniform Pores

The effects of the nature and concentration of surfactants and the preparation conditions on the genesis of iron–zirconium composites with a [Fe³⁺]/[Zr⁴⁺] ratio of 0.123 were studied. The effect of surfactants on the physicochemical properties of precipitates is determined by the conditions of synthesis. The amount of surfactants retained by the precipitate at pH 3 is about an order of magnitude greater than at pH 9. The thermolysis of samples synthesized at acidic pH is accompanied by the dehydration and dehydroxylation of iron–zirconium composites as well as by the decomposition and destruction of surfactants. In the latter processes, compounds or their fragments capable of reducing some phases are removed in a stepped-up manner. The specific surface area of oxide systems formed in this way is at most 100–150 m²/g. In the pH range corresponding to the complete precipitation of the components, highly dispersed single-phase and uniformly porous composites are formed. The choice of a surfactant, its fraction, and preparation conditions enables the preparation of oxides with specific surface areas of 100–400 m²/g. The average pore diameter of the samples ranges from 3.0 to 27.0 nm, and the total pore volume ranges from 0.20 to 0.38 cm³/g.     

Metastable high-spin states in chemical ionization in hydrocarbon combustion

The chemical ionization mechanism for HCO ₂ ⁺ is considered from MINDO/3 CI calculations and ones on the spin-orbit interaction elements, which has been employed in examining the sections of the potential-energy surfaces along the reaction coordinates in the formation of HCO ₂ ⁺ and HCO ₂ ⁺ .Karaganda University. Translated from Teoreticheskaia i ksperimental'naya Khimiya, Vol. 27, No. 6, pp. 672–677, November–December, 1991. Original article submitted April 24, 1989.