A novel catalytic adsorptive stripping voltammetric method for the determination of germanium ultratraces in the presence of chloranilic acid and the V(IV)·HEDTA complex

A novel, sensitive catalytic adsorptive stripping voltammetric procedure which can be used to determine trace amounts of germanium is described. The method is based on the interfacial accumulation of the complex formed by Ge(IV) and the product of the reduction of chloranilic acid on the hanging mercury drop electrode or the renewable silver amalgam film electrode, and its subsequent reduction from the adsorbed state followed by the catalytic action of the V(IV)·HEDTA complex. The presence of V(IV)·HEDTA greatly enhances the adsorptive stripping response of Ge. The reduction of the Ge(IV) in the presence of chloranilic acid and V(IV)·HEDTA was investigated in detail and the effects of pH, electrolyte composition, and instrumental parameters were studied. Under optimal conditions, the catalytic peak current of germanium exhibited good linearity for Ge(IV) concentrations in the range of 0.75–60 nM (for 60 s of accumulation at −0.1 V, r² = 0.995) and a low limit of detection (LOD = 0.085 nM). The procedure was successfully applied to determine Ge in water samples.

     

Soft-templating synthesis and adsorption properties of mesoporous carbons with embedded silver nanoparticles

Mesoporous carbons containing silver nanoparticles have been successfully synthesized under acidic conditions by employing resorcinol and formaldehyde as carbon precursors and triblock copolymer EO₁₀₁PO₅₆EO₁₀₁ (Lutrol F127) as a soft template. Silver nanoparticles of ∼90 nm were added to the synthesis mixture to achieve 10 wt% and 20 wt% of Ag loading in the carbon. Also, tetraethyl orthosilicate (TEOS) was introduced to the system in order to improve adsorption properties of the silver-carbon composites and to reinforce its structure. The resulting carbons with incorporated silver nanoparticles featured high surface areas, large total pore volumes and primary mesopores in the range between ∼6–7 nm.     

How strong can the bend be on a DNA helix from cisplatin? DFT and MP2 quantum chemical calculations of cisplatin-bridged DNA purine bases

The B3LYP/6-31G(d) level of theory was used for the optimization of [Pt(NH(3))(4)](2+), [Pt(NH(3))(3)(H(2)O)](2+), cis-[Pt(NH(3))(2)(H(2)O)(2)](2+), and related platinum complexes. In addition, water or ammonium ligands were replaced by DNA purine bases so that finally cis-diammineplatinum with two bases (Pt-bridged complexes) is obtained. Single point calculations using the MP2/6-31+G(d) method were performed on the obtained reference geometries and were utilized for estimating bond dissociation energies (BDEs) and stabilization energies, and for electron density analyses. After reoptimization, IR spectra were determined from HF second derivatives. It was found that replacement of both water and ammonium by the DNA base is an exothermic process (20-50 kcal/mol depending on the ligands present in the complex). Asymmetric structures with one interbase H-bond were obtained for cis-diammine[bond](N(7),N(7)'-diadenine)[bond]platinum and mixed cis-diammine[bond](N(7)-adenine)[bond](N(7)-guanine)[bond]platinum complexes. In the case of the diguanine Pt-bridge, a symmetrical complex with two ammonium...O(6) H-bonds was found. The higher stabilization energy of the di-guanine complex is linked to a larger component of the Coulombic interaction. However, the BDE of Pt[bond]N(7)(G) is smaller in this complex than the BDE of Pt[bond]N(7)(G) from the mixed Pt[bond]AG complex. Also, steric repulsion of the ligands is about 10 kcal/mol smaller for the asymmetrical Pt[bond]AA and Pt[bond]AG bridges. The influence of the trans effect on DBE can be clearly seen. Adenine exhibits the largest trans effect, followed by guanine, ammonium, and water. The strength of the H-bond can be determined from the IR spectra. The strongest H-bond is the interbase H-bridge between adenine and guanine in the mixed Pt[bond]AG complex; otherwise, the H-bonds of adenine complexes are weaker than in guanine complexes. BDE can be traced in the guanine-containing complexes. The nature of the covalent bonding is analyzed in terms of partial charges and MO. A general explanation of the lower affinity of transition metals to oxygen than nitrogen can be partially seen in the less favorable geometrical orientation of lone electron pairs of oxygen.     

Synthesis and study of new rod-like mesogens containing 2-aminothiophene unit

We present a synthesis and mesomorphic properties of a new series of rod-like mesogens. All the compounds possess a substituted 2-aminothiophene unit as a main element in the structure attached to a stilbene moiety with a terminal alkyloxy chain (OR¹, OR² where R¹=C_nH_2n+1, R²=C_mH_2m+1; n, m ranging from 6 to 12). The synthesis of alkyloxybiphenyl substituted 2-aminothiophenes was carried out by the Gewald reaction and the appropriate reaction conditions were investigated. The liquid–crystalline properties were studied via polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. These materials exhibit nematic and/or smectic A phases. The influence of structural changes (variation in alkyloxy chain length and symmetry of the molecule) on mesogenic behaviour is discussed. Evaluation of UV–vis, fluorescent and electrochemical properties are also included.     

Synthesis,molecular characterisation,and in vivo study of platinum(IV) coordination compounds against B16 mouse melanoma tumours

A novel platinum(IV) coordination compound with 6-mercaptopurine (6-Hmp) has been synthesised and characterised by IR and NMR spectroscopy. Spectroscopic parameters indicate the presence of two chelate (S-6, N-7) monodeprotonated ligands and two chloride ions in the coordination sphere of [PtCl₂(6-mp)₂] · H₂O (I). Two Pt(IV) coordination compounds, [PtCl₂(6-mp)₂] · H₂O (I) and [PtCl₄(dbtp)₂] (II), were used in the in vivo test against B16 mouse melanoma tumours. Cytotoxic activity of compound II against the tumour cells was found to be high (LC₁₀ = 2.6 μM, LC₅₀ = 17.0 μM, LC₉₀ = 58.0 μM) compared to that of cisplatin.     

Quantitative EPR study on free radicals in the natural polyphenols interacting with metal ions and other environmental pollutants

Quantitative electron paramagnetic resonance (EPR) method was applied to characterise radicals stabilised in polyphenolic matrices of various biogenic materials: lichens, mosses, composts, soils, peats, brown coals and sewage sludge sediments. The investigations were carried out on raw materials and extracted fractions of humic acids (HA). General trends of g value and spin concentration changes were found. These parameters in lichens strongly depend on lichen species and air pollution. Determination of the g value and semiquinone spin concentration allows to assess degree of transformation of organic matter in compost, soil, peat and lignite. Application of gaseous ammonia as a base penetrating the organic matrices extends the possibilities and usefulness of the method. Interaction of metal ions with humic materials is illustrated by interaction of VO2+ ion with peat and lignite HA as well as demineralised (raw and carbonised) brown coal. Our investigations demonstrate that quantitative EPR is a rapid and effective monitoring method to study the influence of various environmental factors on substances containing polyphenolic matrices.     

Silica - Titania Support for HVOC's Combustion Catalysts

Preparation of support series for catalysts of combustion of halogenated volatile organic compounds (H-VOC's) was carried out. It was stated that all they allow preparing active catalysts however their main drawback is the lack of hardness against products of H-VOC's combustion e.g. hydrogen chloride and chlorine. Laboratory tests showed that titania and silica - titania supports were characterized by the highest hardness against chlorine derivatives. In comparison to the titania supports, low content (ca. 10 wt.%) silica-containing supports have better mechanical properties, i.e. mechanical strength and attrition resistance. In this paper the method of preparation, composition and physicochemical properties of silica - titania support are presented. This revised version was published online in June 2006 with corrections to the Cover Date.     

Chemometric outlook on correlations between retention parameters of polar and semipolar HPLC columns and physicochemical characteristics of ampholytic substances of biological and pharmaceutical relevance

The Quantitative Property-Retention Relation (QPRR) approach was applied to analyze the correlations between the retention parameters of ampholytic, biologically active substances and their physicochemical (predicted/spectral) characteristics. The retention parameters were obtained for polar and semipolar HPLC columns at various compositions of mobile phases and pH conditions. These values are a unique collection of chromatographic parameters that are a measure of lipophilicity and, consequently, can be very helpful in assessing pharmacological potency of the compounds investigated. Three QPRR models that meet the predictive capability criteria were developed. The relationships can be used to gain pharmacologically interesting information on the biologically active ampholytic substances.

     

Three‐Dimensional Information on the Phase Domain Structure of Thin Films of Polymer Blends Revealed by Secondary Ion Mass Spectrometry

We describe the technique of dynamic secondary ion mass spectrometry developed to determine three‐dimensional phase domain structures of films of polymer blends. The polymers are composed of light elements or are labeled with deuterium or heavy elements. The applicability of this method to various polymer blends forming thin and ultrathin films with flat and undulated air/film interface is discussed.