Speciation of butyltins in fish and sediment by means of gas chromatography with flame photometric detection

A modified method for the determination of tributyl-, dibutyl-, and monobutyl-tin in fish and sediment samples is proposed. The samples are digested with hydrochloric acid and the butyltin compounds are extracted into a tropolone solution in pentane and pentylated by a Grignard reaction. The products are cleaned up by washing with a sodium hyrdoxide solution, dried over sodium sulphate, concentrated by evaporation and analysed by gas chromatography with flame photometric detection, using an interence filter at 610 nm. Problems peculiar to the fish and sediment samples are overcome by this improved clean-up procedure. The limit of detection for tributyltin in fish is 0.04 m?g g^?1 and the reproducibility at 0.06 μg g^?1, expressed as the relative standard deviation, is 6.8%. Contaminated sediment samples were found to contain the mixed methylbutyl-tin compounds Me₂BuSn⁺ and MeBu₂Sn⁺.     

The synthesis and reactivity of ferrocenyloxy)-2-tetrahydropyran

Ferrocenylboronic acid was prepared in good yield via the base hydrolysis of ferrocenylboron dibromide. The ferrocenylboronic acid was converted into hydroxyferrocene which was treated with 2,3-dihydropyran to give (ferrocenyl oxy)-2-tetrahydropyran. Lithiation of this pyran gave the corresponding 2-lithiated ferrocene, which was used to prepare some 1,2-disubstituted ferrocenes including 1-carboxy-2-acetoferrocene (“ferrocenyl-aspirin”).     

Electron transport properties of MgB<Subscript>2</Subscript> in the normal state

We report measurements of the resistivity, ρ, and the Seebeck coefficient, S , of a MgB₂ sintered sample, and compare S with theoretical calculations based on precise electronic structure calculations. ρ is fitted well by a generalized Bloch-Grüneisen equation with a Debye temperature Θ _R of 1050 K. S is given by the sum of a diffusive and a phonon drag term and the behavior in the temperature region T _c < T < 0.1Θ _R follows the relationship AT+BT³. The phonon drag term indicates a strong electron-phonon interaction. The diffusive term, compared with calculations, suggests that σ bands give the main contribution to the Seebeck effect. Received 16 November 2001 and Received in final form 21 December 2001     

Speciation and GC retention indices of some organotin compounds in water

Analytical methods have been developed for the quantitative determination of Bu₄Sn, Bu₃Sn⁺, Bu₂Sn²⁺, BuSn³⁺, Me₃BuSn, Me₂Bu₂Sn, MeBu₃Sn, MeBuSn²⁺, Me₂BuSn⁺ and MeBu₂Sn⁺ in water. Organotin compounds are extracted from water with tropolone at 0.1 % in n-pentane, derivatized with n-pentylmagnesium bromide and determined by gas chromatography with flame photometric detection or flame ionization detection. Absolute detection limits are 0.05-0.12 ng and 1.2-13 ng as tin, respectively. The method was applied to the analysis of spiked tap-water containing 0.3-1000 ng cm^?3 of each of the organotin compounds.     

Fluid motion near the surface of a cylinder in a cross flow

An attempt is made to reconstruct the instantaneous flow structures near the surface of a cylinder from measurements of the various characteristics in the precritical self-similar regime, at the moment of crisis and beyond. Information concerning these structures is of decisive importance in connection with the construction of numerical flow models [1–4] and the reliability and accuracy of the calculation results.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 65–71, July–August, 1989.     

Microanalytical determination of tin in organotin compounds

Existing procedures for the determination of tin in organotin compounds are reviewed, and a new procedure is described which can be used for the rapid microanalysis of most organotin compounds. Wet oxidation with sulphuric acid and 30% hydrogen peroxide is followed by spectrophotometric determination of the extracted ternary tin(IV)-chloride-oxine complex in chloroform. Time for a single determination is 20 min, and the relative standard deviation is 0.7% for 1-5 mg of tin. On account of their volatility, methyltin compounds must be subjected to a sealed-tube wet oxidation in sulphuric-nitric acid mixture. Addition of sulphamic acid after boiling to remove most of the nitric acid makes this compatible with the solvent extraction step. Tin present as organotin stabilizer in PVC samples can also be determined by this method, after destruction of the organic matter with sulphuric acid and 50% hydrogen peroxide.     

Effects of Adsorbed Polyaniline on Redox Processes on As(2)O(3) Surfaces

Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press.