A new sensitive method for the determination of trace mercury by differential pulse polarography: Application to raw salt sample

A new indirect differential pulse polarographic (DPP) method is established for the trace determination of mercury(II). Because of its toxic effects on human health, trace determination of mercury is very important. An indirect method had to be used since no polarographic peak is observed in its direct determination. According to the standard potentials, the reaction between Sn(II) and Hg(II) was found suitable. The peak of Sn(II) at about ?0.40 V is sharp, high and very reproducible, which enables the determination of low concentrations of Hg(II). For this purpose, to a known amount of Sn(II) present in the polarographic cell (acetic acid, HAc, pH 1–2), the unknown Hg(II) sample is added and the quantitative reaction takes place directly in the cell. The Hg(II) concentration is calculated simply from the decrease of the Sn(II) peak. The limit of detection (LOD) was found as 2 × 10^?7 M for S/N = 3. Interferences of some common cations, such as Fe, Cd, Cu, Zn and Pb and anions have been investigated. Only Pb had an overlapping peak with Sn(II). This peak overlap was eliminated simply by working at pH 2 (HAc electrolyte), because of the shift of the Pb peak in the Ac complex to ?0.7 V. This method was successfully applied to synthetic samples and raw salt sample taken from a salt lake in Turkey.     

Synthesis,spectroscopy and X-ray studies of [N′-(2-hydroxy-3-methoxybenzylidene)-4-methylbenzenesulfonohydrazide]uranyl(IV)

The C₃₀H₃₀N₄O₁₀S₂U complex (I) has been investigated and characterized by single crystal X-ray diffraction (CIF file CCDC no. 970349), IR and UV-Vis spectroscopic techniques. X-ray results show that the title compound crystallizes in the monoclinic system, space group P2₁/c with a = 14.8219(14), b = 11.6177(11), c = 20.0854(15) Å, β = 104.268(9)°, V = 3351.9(5) ų and Z = 4. In the title structure, the U atom has a distorted pentagonal-bipyramidal geometry with a tetradentate Schiff base ligand in the equatorial plane and oxo atoms in the axial positions. The C-S-N(H)-N linkage is non-planar, the torsion angle being ?98.7(15)° and the S atom showing a tetrahedral environment. The crystal packing occurs intra-inter molecular N-H?O and C-H?O hydrogen bonds.     

Calculation of Negative Ions of B,C, N,O and F Using Noninteger n Slater Type Orbitals

Combined Hartree‐Fock‐Roothaan calculations have been performed using noninteger n Slater type orbitals for the ground states of the lowest electron configurations 1s²2s²2pⁿ (2 ≤ n ≤ 6) for negative ions of B, C, N, O and F. These results are compared with the corresponding results obtained from the use of integer n Slater type orbitals. All of the nonlinear parameters are fully optimized. The results of calculation of coupling‐projection coefficients, orbital and total energies and virial ratios are presented. It is shown that the noninteger n Slater type orbitals, in general, improve the orbital energies.     

Separation and quantification of the urinary enantiomers of 2-hydroxyglutaric acid by capillary electrophoresis with capacitively coupled contactless conductivity detection: Application to the diagnosis of D- and L-2-hydroxyglutaric aciduria

2-hydroxyglutaric aciduria is an inherited neurometabolic disorder with two major types: D-2-hydroxyglutaric aciduria and L-2-hydroxyglutaric aciduria. An easy and fast capillary electrophoresis system combined with a capacitively coupled contactless conductivity detection method was developed for the enantioseparation and determination of D- and L-2-hydroxyglutaric acid in urine. D- and L-2-hydroxyglutaric acids were separated using vancomycin as the chiral selector. The optimal separation conditions for enantiomers were achieved by the use of a buffer containing 50 mM 4-(N-morpholino) butane sulfonic acid solution (pH 6.5), an electroosmotic flow modifier (0.001% [w/v] polybrene), and 30 mM vancomycin as chiral selector. The analysis time was 6 min under optimal conditions. The optimized and validated method was successfully implemented for quantifying D- and L-2-hydroxyglutaric aciduria in patients’ urine, without any pretreatment step. The linearity of the method was determined to be in the range of 2–100 mg/L for D- and L-2-hydroxyglutaric acid in urine. The precision (relative standard deviation%) was obtained at about 7%. For D- and L-2-hydroxyglutaric acids, the limits of detection were 0.567 and 0.497 mg/L, respectively.     

Planar Dielectrochromatography in a Vertical Chamber

JPC – Journal of Planar Chromatography – Modern TLC - Drawn by capillary forces the developing solvent (mobile phase) migrates through the thin layer (stationary phase) over a defined...     

High-Pressure Densities and Derived Volumetric Properties (Excess,Apparent and Partial Molar Volumes) of Binary Mixtures of Methanol + [BMIM][PF<Subscript>6</Subscript>]

The density of five (0.02297, 0.08317, 0.26147, 0.49343, 0.75255 mole fraction BMIMPF₆) binary methanol + BMIMPF₆ (1-n-butyl-3-methylimidazolium hexafluorophospate) mixtures have been measured with a vibrating-tube densimeter. Measurements were performed at temperatures from 298 to 398 K and at pressures up to 40 MPa. The total uncertainties of the density, temperature, pressure, and concentration (mole fractions) measurements were estimated to be less than 0.1 kg⋅m⁻³, 15 mK, 5 kPa, and 10⁻⁴, respectively. The uncertainties reported in this paper are expanded uncertainties at the 95% confidence level with a coverage factor of k=2. The measured densities were used to study of the effect of temperature, pressure, and concentration on the derived volumetric properties such as excess, apparent and partial molar volumes. It is shown that the values of excess molar volume for methanol + BMIMPF₆ mixtures are negative at all measured temperatures and pressures in the whole concentration range. The measured densities were used to develop Tait-type equations of state for pure components and the mixtures. The structural properties such as direct and total correlation function integrals were calculated using the derived partial molar volumes at infinite dilution.     

Relationship between current response and time in ion transport problem including diffusion and convection. 2. Numerical approach

The mathematical model related to controlled potential experiments in electrochemistry is studied. Ion transport is regarded as the superposition of diffusion and migration under the influence of an electric field. Modeling of the experiment leads to the nonlocal identification problem for nonlinear parabolic equation. It is shown that in some cases the nonlocal identification problem can be transformed to an initial value problem for nonlinear parabolic equation. The finite diference approximation of this problem, with the appropriate iteration algorithm, is derived. Based on these algorithms the solution of the identification problem is presented. The obtained results permits one to derive the behaviour of the current response , depending on time, also the relationship between the current response and Gottrellian is obtained in explicit form. An influence of the valences oxidised and reduced species is also analyzed.      

Syntheses,IR spectra,thermal properties and crystal structures of novel cyano-bridged polymeric complexes of zinc and cadmium with tetracyanoplatinate

Two novel one-dimensional polymeric cyano-bridged platinum(II) complexes of N-(2-hydroxyethyl)-ethylenediamine (hydeten), [M^II(hydeten)Pt(CN)₂(μ-CN)₂]_n (M^II = Zn^II (1) and Cd^II (2)), were synthesized and characterized by physico-chemical methods (elemental analysis, IR spectroscopy and thermoanalytical measurements) and X-ray diffraction. Thermal behaviours of 1 and 2 were followed using TG and DTA (DSC) techniques. The 1D chain structures of 1 and 2 were verified by X-ray diffraction studies. According to the positions of the bridging cyano groups, in complex 1 the polymeric chains are built up via the 2,2-CT type, while in complex 2 the polymeric chains are built up via the 2,2-TT type.     

Minimal homogeneous Steiner 2-(v,3) trades

A Steiner 2-$(v,3)$ trade is a pair $(T_1,T_2)$ of disjoint partial Steiner triple systems, each on the same set of $v$ points, such that each pair of points occurs in $T_1$ if and only if it occurs in $T_2$. A Steiner 2-$(v,3)$ trade is called d-homogeneous if each point occurs in exactly d blocks of $T_1$ (or $T_2$). In this paper we construct minimal d-homogeneous Steiner 2-$(v,3)$ trades of foundation $v$ and volume $\mathit{dv}/3$ for sufficiently large values of $v$. (Specifically, $v>3(1.75d^2+3)$ if $v$ is divisible by 3 and $v>d(4^{d/3+1}+1)$ otherwise.)     

Electrical conductivity,photoconductivity, and optical properties of poly(1,4‐diaminoanthraquinone) organic semiconductor for optoelectronic applications

The electrical conductivity and optical properties of the poly(1,4‐diaminoanthraquinone) [poly(1,4‐DAAQ)] have been investigated. The electrical conductivity of the polymer increases with temperature and room temperature conductivity was found to be 2.68 10^?5 S cm^?1. The optical band gap of the polymer is 1.87 eV due to the direct optical transitions. The photoconductivity of the polymer is higher than that of dark conductivity. When the light is switched on, the resistance decreases abruptly and when it is switched off, the resistance increases. This confirms that the polymer is a photoconductive material. The obtained results indicate that the poly(1,4‐DAAQ) is a photoconducting organic semiconductor with photovoltaic and dark current properties. Copyright © 2008 John Wiley & Sons, Ltd.