Inner-sphere oxidation of a ternary dipicolinatochromium(III) complex involving a malonic acid co-ligand

The oxidation of a ternary complex of chromium(III), [Cr^III(DPA)(Mal)(H₂O)₂]^?, involving dipicolinic acid (DPA) as primary ligand and malonic acid (Mal) as co-ligand, was investigated in aqueous acidic medium. The periodate oxidation kinetics of [Cr^III(DPA)(Mal)(H₂O)₂]^? to give Cr(VI) under pseudo-first-order conditions were studied at various pH, ionic strength and temperature values. The kinetic equation was found to be as follows: \( {\text{Rate}} = {{\left[ {{\text{IO}}_{4}^{ - } } \right]\left[ {{\text{Cr}}^{\text{III}} } \right]_{\text{T}} \left( {{{k_{5} K_{5} + k_{6} K_{4} K_{6} } \mathord{\left/ {\vphantom {{k_{5} K_{5} + k_{6} K_{4} K_{6} } {\left[ {{\text{H}}^{ + } } \right]}}} \right. \kern-0pt} {\left[ {{\text{H}}^{ + } } \right]}}} \right)} \mathord{\left/ {\vphantom {{\left[ {{\text{IO}}_{4}^{ - } } \right]\left[ {{\text{Cr}}^{\text{III}} } \right]_{\text{T}} \left( {{{k_{5} K_{5} + k_{6} K_{4} K_{6} } \mathord{\left/ {\vphantom {{k_{5} K_{5} + k_{6} K_{4} K_{6} } {\left[ {{\text{H}}^{ + } } \right]}}} \right. \kern-0pt} {\left[ {{\text{H}}^{ + } } \right]}}} \right)} {\left\{ {\left( {\left[ {{\text{H}}^{ + } } \right] + K_{4} } \right) + \left( {K_{5} \left[ {{\text{H}}^{ + } } \right] + K_{6} K_{4} } \right)\left[ {{\text{IO}}_{4}^{ - } } \right]} \right\}}}} \right. \kern-0pt} {\left\{ {\left( {\left[ {{\text{H}}^{ + } } \right] + K_{4} } \right) + \left( {K_{5} \left[ {{\text{H}}^{ + } } \right] + K_{6} K_{4} } \right)\left[ {{\text{IO}}_{4}^{ - } } \right]} \right\}}} \) where k ₆ (3.65 × 10^?3 s^?1) represents the electron transfer reaction rate constant and K ₄ (4.60 × 10^?4 mol dm^?3) represents the dissociation constant for the reaction \( \left[ {{\text{Cr}}^{\text{III}} \left( {\text{DPA}} \right)\left( {\text{Mal}} \right)\left( {{\text{H}}_{2} {\text{O}}} \right)_{2} } \right]^{ - } \rightleftharpoons \left[ {{\text{Cr}}^{\text{III}} \left( {\text{DPA}} \right)\left( {\text{Mal}} \right)\left( {{\text{H}}_{2} {\text{O}}} \right)\left( {\text{OH}} \right)} \right]^{2 - } + {\text{H}}^{ + } \) and K ₅ (1.87 mol^?1 dm³) and K ₆ (22.83 mol^?1 dm³) represent the pre-equilibrium formation constants at 30 °C and I = 0.2 mol dm^?3. Hexadecyltrimethylammonium bromide (CTAB) was found to enhance the reaction rate, whereas sodium dodecyl sulfate (SDS) had no effect. The thermodynamic activation parameters were estimated, and the oxidation is proposed to proceed via an inner-sphere mechanism involving the coordination of IO₄ ^? to Cr(III).     

Nondestructive neutron activation analysis of some soil clays of Egypt

Fourteen clay samples separated from calcareous, lacustrine, Nile alluvium and desert alluvium soils of Egypt were analyzed by pure instrumental neutron activation analysis. Elemental composition was determined by high resolution gamma-spectrometry on samples irradiated with reactor neutrons using the monostrandard technique. This was carried out in the nuclear research center of Karlsruhe, West Germany. As many as 17 trace elements, beside Ca, K, and Na, were quantitatively determined. The spectra of chosen activated clays are given. Data reveal that the content of the trace elements As, Cs, Hf, Sb, Sc, Sm, Yb, Th and U were found within a narrow range despite location and depths of clay samples. Nevertheless, the contents of some elements mainly Ce, Cr and La had a wide range. In brief, the presence of any elements in higher or lower levels in certain clays is contingent on the occurence of its bearing minerals, nature of parent sediments and depositional environments of these sediments.     

Determination of glucosamine and carisoprodol in pharmaceutical formulations by LC with pre-column derivatization and UV detection

A simple and reliable precolumn derivatization liquid chromatography method with ultraviolet detection has been developed and validated for the analysis of glucosamine (GS) in various dietary supplement formulations and raw materials. Additionally, the proposed method was used for analysis of carisoprodol (CR) found in ternary mixture with paracetamol (PR) and caffeine (CF). The linearity ranges were 1-100 μg/mL for GS, 1-150 μg/mL for CR, PR and CF. Derivatization was used with 1,2-naphthoquinone-4-sulphonic acid sodium salt in the presence of borate buffer. Chromatographic separation of GS-naphthoquinone derivative was achieved by using a mixture of acetonitrile and water (pH 7.3 adjusted with 0.1 M NaOH) in the ratio 10:90, v/v and flow-rate of 1.0 mL/min. UV detection was carried out at 280 nm. For PR, CF, and CR-naphthoquinone derivative, the chromatographic separation was achieved by using mixture of acetonitrile and 20 mM KH(2)PO(4) (pH 3.0 adjusted with phosphoric acid) in the ratio 20:80, v/v and flow-rate of 1.0 mL/min. UV detection was carried out at 275 nm. The limits of detection were 37.2, 35.9, 30.4 and 40.0 ng/mL for GS, CR, PR and CF, respectively.     

Solutions to Class of Linear and Nonlinear Fractional Differential Equations

In this paper, the fractional auxiliary sub-equation expansion method is proposed to solve nonlinear fractional differential equations. To illustrate the effectiveness of the method, we discuss the space-time fractional Kd V equation, the space-time fractional RLW equation, the space-time fractional Boussinesq equation, and the(3+1)-spacetime fractional ZK equation. The solutions are expressed in terms of fractional hyperbolic and fractional trigonometric functions. These solutions are useful to understand the mechanisms of the complicated nonlinear physical phenomena and fractional differential equations. Among these solutions, some are found for the first time. The analytical solution of homogenous linear FDEs with constant coefficients are obtained by using the series and the Mittag–Leffler function methods. The obtained results recover the well-know solutions when α = 1.     

Separation and structural studies of manganese(II), cobalt(II), nickel(II), copper(II) and cadmium(II) complexes of benzilic and mandelic esters

Summary Solid metal complexes of benzilic and mandelic esters have been prepared and their structure elucidated using vis., i.r., n.m.r. and e.s.r. spectra. The results of elemental analysis are commensurate with the proposed formulae. Spectral studies indicate that the Ni complexes are octahedral, whereas the Co and Cu analogoues are distorted octahedral.     

Estimation of calcified tissues hardness via calcium and magnesium ionic to atomic line intensity ratio in laser induced breakdown spectra

Calcified tissues representing three different matrices, namely enamel of human teeth, shells and eggshell, have been studied via Laser Induced Breakdown Spectroscopy (LIBS) technique. The experimental CaII/CaI and MgII/MgI ratios have been measured, in view of the expected correlation between the extent of ionization caused by the laser induced shock wave (SW) and the hardness of the target. The ratio CaII/CaI between the ionic calcium line at 373.69 nm and the neutral line at 428.9 nm is obtained for enamel, shells and eggshell spectra, as well as the ratio MgII/MgI between the ionic magnesium line at 280.26 nm and the neutral line at 285.22 nm. The results show that such spectral lines intensities ratio differs for different matrices and is indeed related to the target materials hardness. It is also found that the MgII/MgI ratio is preferable as an indicator of hardness since these lines are less affected by self absorption. The SW front speed has been measured in the three cases and the obtained values confirm the proportionality to the target hardness. The results here obtained suggest the feasibility of the quantitative estimation of hardness for any other calcified tissues.     

HPLC method for the simultaneous determination of atenolol and chlorthalidone in human breast milk

A high-performance liquid chromatographic method was optimized and validated for the determination of atenolol and chlorthalidone (CT) in human breast milk. The milk samples were extracted and purified using ACN and phosphoric acid for precipitation of proteins followed by removal of ACN and milk fats by extraction with methylene chloride. The samples were applied, after an extraction procedure, to a cyanide column using a mobile phase consisting of ACN/water (35:65 v/v) and buffered at pH 4.0 with flow rate of 1.0 mL/min. Quantitation was achieved with UV detection at 225 nm using guaifenesin as the internal standard. The effectiveness of protein precipitation and clean up procedure were investigated. The method was validated over the range of 0.3-20 microg/mL for atenolol and 0.25-5 microg/mL for CT.     

Validated Optimized Method for Simultaneous Analysis of Active Silymarin Components and Dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene Dioxybiphenyl-2,2′-dicarboxylate in a Pharmaceutical Preparation by Use of a Monolithic Silica C18 Column

A simple, rapid, and sensitive isocratic reversed-phase LC method using a monolithic column has been developed and validated for simultaneous analysis of the active components of silymarin [taxifolin, silydianin, silychristin, diastereomers of silybin (silybin A and B), and diastereomers of isosilybin (isosilybin A and B)] and dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate in a commercial formulation. The mobile phase was a 45:55 (v/v) mixture of methanol and 5 mM NaH₂PO₄ (adjusted to pH 2.75 with phosphoric acid) at a flow rate of 1.5 mL min^?1. UV detection was performed at 288 nm and quantification was based on peak area. The method was validated for linearity, accuracy, precision, selectivity, and robustness.