Stripping voltammetric determination of platinum metals at a carbon paste electrode modified with cationic surfactants

In this contribution, a novel method is described for the determination of platinum metals. The procedure developed employs a carbon paste electrode modified in situ with cationic surfactants of the quaternary ammonium salt type. The pre-concentration step is based on a specific accumulation mechanism involving ion-pair formation; the detection being performed by cathodic scanning in the differential pulse voltammetric mode. Regarding the individual forms of platinum metals, the method has been found convenient for the determination of three heavy platinum metals in the form of Pt(IV), Ir(III) and Os(IV), whereas for the remaining elements (Ru, Rh, and Pd) was almost inapplicable. Platinum metals of the former group can be pre-concentrated in chloride-containing supporting media via PtCl₆²⁻, IrCl₆³⁻ and OsCl₆²⁻ complex anions, the central atom of each species being fairly reducible during the voltammetric scan. Stripping signals for both platinum and iridium were proportional to the concentration in a range of 1-10 × 10⁻⁶ M Pt(IV) and Ir(III); the response for osmium being linear within 0.1-6 × 10⁻⁷ M Os(IV) with a detection limit of about 5 × 10⁻⁹ mol l⁻¹. During optimisation, special attention was paid to the accumulation mechanism, choice of key experimental conditions, and to interference effects from foreign ions with potentially ion-pairing capabilities (AuCl₄⁻, TlCl₄⁻, CrO₄²⁻, MnO₄⁻, SCN⁻, and I⁻). The method elaborated has been tested on both model solutions and real samples of industrial waste water, showing in both cases satisfactory analytical performance.     

Some remarks on the degrees of faithful irreducible representations

We study a class of finite p-groups admitting faithful irreducible complex representations of distinct degrees. In particular, for every prime p, we produce an example of such a p-group having minimal order p ⁸.Dedicated to A. Wagner on the occasion of his 60th birthdayLavoro eseguito nell'ambito dei finanziamenti M.U.R.S.T.     

Synthesis and properties of α-sulfo carboxyl disodium salt

The synthesis and properties of α-sulfo carboxyl disodium salt (SCDS) were studied in detail for the first time in this paper. SCDS was synthesized via saponification reaction of fatty acid methyl ester sulfonate sodium (MES). FT-IR was used to characterize the molecular structure of target product. The yield of disodium salt was greater than 98% by two-phase titration. The performance of SCDS was studied and was compared with raw materials MES, conventional anionic surfactant AES and nonionic surfactant AEO₉. The result shows SCDS can reduce the surface tension of the solution to 27.89?mN/m at critical micelle concentration (CMC). The wetting ability of SCDS was significantly enhanced with the increase of temperature. The emulsification effect of SCDS on the soybean oil is better than that on the liquid paraffin. Surprisingly, SCDS has a good foamability and foaming stability.     

Properties of Film Materials Based on Composite Nanofibers from Aliphatic Copolyamide and Carbon Nanotubes for Tissue Engineering

The investigation of the dependence of effective viscosity on shear rate for a water-alcohol solution of an aliphatic copolyamide and its mixtures with single-wall carbon nanotubes reveals that additives of the nanoparticles in the amount of 0.5 wt % lead to a substantial reduction in the effective viscosity as the shear rate rises. The measurement of the surface tension and electrical conductivity of the solutions bearing 0.1–2.0 wt % of the nanotubes allows one to choose an optimal mode for electrospinning of the composite nanofibers based on the aliphatic copolyamide. The introduction of carbon nanofibers reduces the specific resistance of the material to 8.9 × 10⁹ Ω m, but increases the elastic modulus. The lack of cytotoxicity of the resulting materials and the high proliferative activity of human dermal fibroblasts on their surface allow one to use the film materials based on the composite nanofibers in cell technologies and as matrices for tissue engineering.     

New hierarchical titania-based structures for photocatalysis

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Multivariate Normal Approximation on the Wiener Space: New Bounds in the Convex Distance

Journal of Theoretical Probability - We establish explicit bounds on the convex distance between the distribution of a vector of smooth functionals of a Gaussian field and that of a normal vector...     

The synthesis of some bidentate ligands containing both phosphine and nitrile groups

Both (C₆H₅)₂P(CH₂)₃CN and (C₆H₅)₂P(CH₂)₄CN have been obtained from the reaction of Br(CH₂)_nCN (n = 3, 4) with (C₆H₅)₂POCH₃ followed by reduction with (C₆H₅)₂SiH₂. These phosphine-nitrile ligands form L₂PdCl₂ complexes which are shown by IR measurements to have trans geometries with the phosphine portions of the ligands coordinated. Reactions of o-BrC₆H₄CN with CH₃(CH₂)₃Li followed by R₂PCl (R = C₆H₅ or (CH₃)₂N) have been used to provide good yields of the corresponding R₂P-o-C₆H₄CN products.     

Thermo-oxidative degradation of some elastomers with a high content of 3,4 isoprene units

New elastomers with high content of 3,4 isoprene units have been developed during the last decades in an attempt to ensure superior performances of the final products and the present study is devoted to the investigation of some peculiarities of their ageing behaviour. On thermo-oxidative degradation, 3,4 isoprene units are less affected in comparison to cis-1, 4 and trans-1, 4 isoprene units. The degradation process consists mainly in splitting of the main chains at temperatures of 80–100 °C while at higher temperatures (120–130 °C) branching becomes a significant modification and this reaction is enhanced for the polymers containing preponderantly 3,4 units. Such behaviour leads to the fact that the processability of polymers containing high amounts of 1,2 and 1,3 isoprene units is less affected by thermo-oxidative degradation in comparison with cis-1, 4-polyisoprene, which could be explained by the fact that large amounts of double bonds are not present in the backbone of macromolecules but in the pendent groups.