Determination of lead, copper and manganese by graphite furnace atomic absorption spectrometry after separation/concentration using a water-soluble polymer

In this study, a water-soluble polymer, polyvinylpyrrolidinone (PVP) having chelating functionalities was used for the preconcentration and separation of traces of Pb, Cu, Ve and Mn prior to their determination by graphite furnace atomic absorption spectrometry. For this purpose, the sample and the PVP solutions were mixed and the metal bound polymer was precipitated by adding the mixture onto acetone. The precipitate was separated by decantation and dissolved with water. By increasing the ratio of the volumes of sample to water used in dissolving the precipitate, the analyte elements were concentrated as needed. The concentration of trace elements was determined using graphite furnace atomic absorption spectrometry. The analyte elements in matrix free aqueous solutions were quantitatively recovered. The validity of the proposed method was checked with a standard reference material (NIST SRM 1577b bovine liver) and spiked fruit juice, sea water and mineral water samples. The analytical results were found to be in good agreement with certified and added values. Detection limits (3δ) were 1.7, 3.6 and 4.1 μg l⁻¹ for Pb, Cu and Mn, respectively, using 10 μl of sample volume. The method is novel and can be characterized by rapidity, simplicity, quantitative recovery and high reproducibility.     

The strong solution of the Monge–Ampère equation on the Wiener space for log-concave densities

Let (W,H,μ) be an abstract Wiener space, assume that $\text{d}\text{ν=L}\text{d}\text{μ}$ is a second probability measures on $\text{(W,}\text{B}\text{(W))}$ such that $\text{L=}\text{1}\text{c}\text{exp}\text{?f}$, with $\text{f∈}\text{D}{}_{\mathrm{2,1}}$ lower bounded and H-convex. Let $\text{T=I}{}_{\mathrm{W}}\text{+??,}\text{?∈}\text{D}{}_{\mathrm{2,1}}$, be the solution of the Monge problem transporting μ to ν and realizing the H-Wasserstein distance between μ and ν. We prove that $\text{?∈}\text{D}{}_{\mathrm{2,2}}$ hence the Gaussian Jacobian $\text{Λ=}\text{det}{}_2\text{(I+?}{}^2\text{?)}\text{exp}\text{{}\text{L}\text{??1/2|??|}{}_{\mathrm{H}}{}^2\text{}}$ is well-defined and T is the strong solution of the Monge–Ampère equation ΛL°T=1 a.s. on W. To cite this article: D. Feyel, A.S. Üstünel, C. R. Acad. Sci. Paris, Ser. I 339 (2004).     

Determination of lead and nickel in Apple-Leaves and sea-water by electrothermal atomic absorption spectrometry after solid-phase extraction using Chromosorb-107 filled in a syringe

Lead and nickel were concentrated and separated after sorbing on Chromosorb-107 filled in a syringe prior to their determination by electrothermal atomic absorption spectrometry. To retain the analytes, the sample solution treated with or without ammonium pyrolidine dithiocarbamate (APDC) was drawn into the syringe filled with Chromosorb-107 and discharged back manually. Then the analyte elements were eluted by drawing and discharging the suitable eluent. The optimum experimental conditions for quantitative recoveries of analytes (amount of sorbent, pH of sample, concentration and kind of eluent, flow rates of sample and eluent and adding of the effect of complexing agent) were investigated. Nickel was quantitatively retained at pH6 irrespective of whether it was complexed with APDC while the quantitative sorption of lead was achieved at pH8 only if it was treated with APDC prior to passing through the sorbent. The lead and nickel retained on the sorbent were eluted drawing and discharging 4.5 M HNO(3), respectively. If the concentration of analyte elements in the sample were too low to be detected, then they were concentrated by increasing the ratio of sample value to eluent volume as needed. The lead and nickel in spiked sea-water samples and in certified reference Apple-Leaves (NIST SRM 1515) standards were quantitatively (95%) recovered with R.S.D. of around +/-2%.     

A rapid solid sampling method for determination of nickel and copper along human hair by ETAAS

A procedure for copper and nickel determination in scalp hair by solid sampling electrothermal atomic absorption spectrometric method was described. The hair samples (0.02 to 0.4 mg) were inserted directly on the platforms of solid sampling autosampler. The effects of pyrolysis temperature, atomization temperature, the amount of sample as well as addition of a modifier (Pd/Mg) and/or auxiliary digesting agents (hydrogen peroxide and nitric acid) and/or a surfactant (Triton X-100) on the determination of copper and nickel by solid sampling atomic absorption spectrometry were investigated. After optimization of parameters, the average recoveries of copper in two different certified reference hair samples were 105.7 and 97.6%. The recoveries of nickel in the both certified reference hair samples were in 95.2 and 96.4%. The limits of detection (3σ, N = 10) for copper and nickel were 22 ng/g and 35 ng/g, respectively. Heterogenous distribution of analyte in microscale for segmental analysis could be determined which is important to know that analyte quantity and time of poisoning of a person was exposed. For this purpose, 0.5 cm of pieces were cut along one or a few close strands and analyzed by solid sampling. This process could not be performed by wet-digestion method because 50 mg of sample is needed each time. Finally, the method was applied for the determination of copper and nickel concentrations in the hairs of different persons.     

The use of gold nanoparticles as an effective modifier for the determination of arsenic and antimony by electrothermal atomic absorption spectrometry

Gold nanoparticles (AuNPs) were used as a new chemical modifier for the determination of arsenic and antimony in salt solutions by electrothermal atomic absorption spectrometry. The AuNPs were prepared by reducing chloroauric acid with sodium citrate. The effects of pyrolysis and atomization temperatures, the amounts of interferents and modifier on the sensitivities of arsenic and antimony were investigated. As and Sb remain in the graphite tube up to 1,100°C, which is sufficient for the determination of the two metals in certified reference materials and spiked sea water samples within a 95% confidence level with low RSD (<10%). The detection limits (N?=?10 at 3??) for As and Sb in sea water are 2.3???g?L^-1 and 3.0???g?L^-1, respectively. Almost no background as well as a blank value was detected for AuNPs.

An entry to the azocino[4,3-b]indole framework through a dehydrogenative activation of 1,2,3,4-tetrahydrocarbazoles mediated by DDQ: formal synthesis of (±)-uleine

It is presented that hexahydro-1,5-methano[4,3-b]indoles were efficiently synthesized in high yields (up to 89% yield) through the cyclization reaction of starting tetrahydrocarbazoles bearing a monoalkylaminocarbonylmethyl moiety at the C-2 position mediated by 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ). A mechanistic proposal is also given that mainly includes two cascade reactions: (i) formation of a vinylogous iminium cation via DDQ-mediated dehydrogenation of tetrahydrocarbazole functionality and (ii) intra-molecular and syn-selective addition of the amide functionality as the nucleophile to the vinylogous iminium cation. Furthermore, this cyclization reaction was successfully utilized in the formal total synthesis of (±)-uleine, an Aspidospermatan skeletal type alkaloid.     

Decomposition algorithms for locating minimal cuts in a network

This paper provides decomposition algorithms for locating minimal cuts in a large directed network. The main theorem provides several cases for the algorithms. In the worst case, it is shown that the efficiency of one of the proposed algorithms is of the same order as a no-decomposition algorithm. As in linear programming, the obvious advantage of the proposed decomposition procedure is its ability to potentially handle larger problems than a no-decomposition algorithm.     

Chloro-Modified Magnetic Fe3O4@MCM-41 Core–Shell Nanoparticles for L-Asparaginase Immobilization with Improved Catalytic Activity,Reusability, and Storage Stability

This paper describes a new support that permits to efficient immobilization of L-asparaginase (L-ASNase). For this purpose, Fe₃O₄ magnetic nanoparticles were synthesized and coated by MCM-41. 3-chloropropyltrimethoxysilane (CPTMS) was used as a surface modifying agent for covalent immobilization of L-ASNase on the magnetic nanoparticles. The chemical structure; thermal, morphological, and magnetic properties; chemical composition; and zeta potential value of Fe₃O₄@MCM-41-Cl were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction patterns (XRD), and zeta-potential measurement. The immobilization efficiency onto Fe₃O₄@MCM-41-Cl was detected as 63%. The reusability, storage, pH, and thermal stabilities of the immobilized L-ASNase were investigated and compared to that of soluble one. The immobilized enzyme maintained 42.2% of its original activity after 18 cycles of reuse. Furthermore, it was more stable towards pH and temperature compared with soluble enzyme. The Michaelis–Menten kinetic properties of immobilized L-ASNase showed a lower V_max and a similar K_m compared to soluble L-ASNase. Immobilized enzyme had around 47 and 32.5% residual activity upon storage a period of 28 days at 4 and 25 °C, respectively. In conclusion, the Fe₃O₄@MCM-41-Cl@L-ASNase core–shell nanoparticles could successfully be used in industrial and medical applications.

     

Ab initio study of the linear and nonlinear optical responses in BiAlO3

The linear and non-linear optical properties of BiAlO₃ are studied by employing the density functional perturbation theory within the local density and generalized gradient approximations. The computations are based on the electronic structure obtained within density functional theory. The optical properties such as the dielectric function, refractive index, spectral reflectivity, absorption coefficient and electron energy-loss spectrum are obtained in the energy region of up to 30 eV. The calculated value of the birefringence for BiAlO₃ shows that it is a uniaxial negative crystal and has a large birefringence. We also report our studies on the second harmonic generation response coefficient over a large frequency range for BiAlO₃ crystal. The predicted second-order optical spectra indicate pronounced structures related to of 1ω and 2ω frequency resonances. Furthermore, the non-linear optic and linear electro-optic coefficients are computed by employing 2n + 1 theorem applied to an electric-field dependent energy functional. The results are compared with the available calculations.     

Ion‐exchanger synthesis using reversible addition‐fragmentation chain transfer polymerization

An ion‐exchanger with polyanionic molecular brushes was synthesized by a “grafting from” route based on “surface‐controlled reversible addition‐fragmentation chain transfer polymerization” (RAFT). The RAFT agent, PhC(S)SMgBr was covalently attached to monodisperse‐porous poly(dihydroxypropyl methacrylate‐co‐ethylene dimethacrylate), poly(DHPM‐co‐EDM) particles 5.8 μm in size. The monomer, 3‐sulfopropyl methacrylate (SPM), was grafted from the surface of poly(DHPM‐co‐EDM) particles with an immobilized chain transfer agent by the proposed RAFT protocol. The degree of polymerization of SPM (i. e. the molecular length of the polyanionic ligand) on the particles was controlled by varying the molar ratio of monomer/RAFT agent. The particles carrying polyanionic molecular brushes with different lengths were tested as packing material in the separation of proteins by ion exchange chromatography. The columns packed with the particles carrying relatively longer polyanionic ligands exhibited higher separation efficiency in the separation of four proteins. Plate heights between 130–200 μm were obtained. The ion‐exchanger having poly‐(SPM) ligand with lower degree of polymerization provided better peak‐resolutions on applying a salt gradient with higher slope. The molecular length and the ion‐exchanger group content of polyionic ligand were adjusted by controlling the degree of polymerization and the grafting density, respectively. This property allowed control of the separation performance of the ion‐exchanger packing.