Sensitivity Enhancement in Uranium Determination by UV-Visible Spectroscopy Using Ion Imprinted Polymer

There is need to determination of uranium concentration at ppb level in environmental matrices. Due to low sensitivity of FAAS, UV-Visible Spectroscopy is generally used as measurement technique. In this study, ion-imprinted polymers (IIP) were prepared for uranyl ion (imprint ion) by formation of ternary (salicylaldoxime and 4-vinylpyridine) complex in 2-methoxy ethanol (porogen) following copolymerization with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking monomer using 2,2-azobisisobutyronitrile as initiator. The synthesized polymers were characterized by FT-IR and TGA analysis. Arsenazo Ⅲ in 3 M HClO₄ was used as complexing agent in the measurement step. The optimal pH for preconcentration was found to be between 3.5～6.5 values. The developed method was applied to uranium (Ⅵ) determination in natural water samples.     

Cyclohexylamine) 2 M(CN) 4 ⋅2C 6 H 6 (M = Cd or Hg)

Two new title compounds have been prepared in powder form. Their spectral data are found to be consistent with the structure foundin Hofmann-T_d-type clathrates.     

The relaxed Newton method derivative: Its dynamics and non-linear properties

The dynamic behaviour of the one-dimensional family of maps f(x)=_c2[(a−1)x+_c1]^{−λ/(α−1)}$f\left(x\right)=c_2{[(a-1)x+c_1]}^{-\lambda /(\alpha -1)}$ is examined, for representative values of the control parameters a,_c1$a,c_1$, _c2$c_2$ and λ$\lambda$. The maps under consideration are of special interest, since they are solutions of the relaxed Newton method derivative being equal to a constant a$a$. The maps f(x)$f\left(x\right)$ are also proved to be solutions of a non-linear differential equation with outstanding applications in the field of power electronics. The recurrent form of these maps, after excessive iterations, shows, in an _xn$x_n$ versus λ$\lambda$ plot, an initial exponential decay followed by a bifurcation. The value of λ$\lambda$ at which this bifurcation takes place depends on the values of the parameters a,_c1$a,c_1$ and _c2$c_2$. This corresponds to a switch to an oscillatory behaviour with amplitudes of f(x)$f\left(x\right)$ undergoing a period doubling. For values of a$a$ higher than 1 and at higher values of λ$\lambda$ a reverse bifurcation occurs. The corresponding branches converge and a bleb is formed for values of the parameter _c1$c_1$ between 1 and 1.20. This behaviour is confirmed by calculating the corresponding Lyapunov exponents.     

On closed timelike and spacelike ruled surfaces

In this study, by using the concepts and results on spherical curves in dual Lorentzian space, we give the criterions for ruled surfaces with non‐lightlike ruling to be closed (periodic). Moreover, we obtain the necessary and sufficient conditions to guarantee that a timelike or a spacelike ruled surface is closed (periodic). Copyright © 2016 John Wiley & Sons, Ltd.     

Comparison of different extraction and detection methods for sugars using amino-bonded phase HPLC

In this study, different methods are compared in order to quantitate individual sugars extracted from apple samples using methanol and water. Glucose, fructose, and sucrose are separated in 20 min using an amino-bonded carbohydrate column and a 75:25 acetonitrile-water mobile phase, followed by UV (190 nm) and refractive index detection. Variations in the sugar profiles are observed using different extraction or detection methods (or both) at a 1.4-mL/min flow rate. The data obtained show differences (p < 0.01) from both extraction or detection methods. The highest contents of free sugars studied occur in samples extracted with water.     

Speciation of lead in soils and relation with its concentration in fruits

The lead concentrations of the fruit samples were determined by using slotted tube atom trap (STAT)-enrichment-flame and graphite furnace atomic absorption spectrometry (FAAS and GF-AAS). The soil samples related to these fruits were also analysed for Pb after extraction with various chemical reagents. The relation between the fruit-lead and soil-extractable lead concentrations was examined in order to explain the bioavailability of lead. A linear relation was observed between the hot Na₂EDTA extraction-soluble Pb contents in the soil and the Pb concentrations in the mulberry (R²=0.95), strawberry and apple grown on these soils. Probable chemical forms of lead in soil were evaluated. Acceptable agreement (at least 91%) was achieved between the results of STAT-enrichment-FAAS and GF-AAS.     

Development of a cloud point extraction and preconcentration method for chromium(III) and total chromium prior to flame atomic absorption spectrometry

A sensitive and selective method has been developed for the determination of chromium in water samples based on using cloud point extraction (CPE) preconcentration and determination by flame atomic absorption spectrometry (FAAS). The method is based on the complexation of Cr(III) ions with Brilliant Cresyl Blue (BCB) in the presence of non-ionic surfactant Triton X-114. Under the optimum conditions, the preconcentration of 50 mL of water sample in the presence of 0.5 g/L Triton X-114 and 1.2 × 10⁻⁵ M BCB permitted the detection of 0.42 μg/L chromium(III). The calibration graph was linear in the range of 1.5–70 μg/L, and the recovery of more than 99% was achieved. The proposed method was used in FAAS determination of Cr(III) in water samples and certified water samples. In addition, the developed CPE-FAAS method was also used for speciation of the inorganic chromium species after reduction of Cr(VI) to Cr(III) using a thiosulphate solution of 120 mg/L in the presence of Hg(II) ion as a stabilizer.     

A Sensitive and Selective RP-LC Method for the Simultaneous Determination of the Antihypertensive Drugs, Enalapril, Lercanidipine, Nitrendipine and Their Validation

A RP-LC method is presented, which is sensitive and selective for the simultaneous determination of enalapril–lercanidipine and enalapril–nitrendipine binary mixtures in their pharmaceutical dosage forms. The analyte peaks were detected using the LC method with the mobile phase ratio of methanol: water (70:30 v/v, pH 3.0) and a 1.0 mL min^?1 flow rate. The detection wavelength was selected at 210 nm using photo diode array detector and column temperature was optimized to 30 °C. Linearity was obtained at different concentration ranges for all working pharmaceutically active compounds between 0.5 and 25 μg mL^?1. The proposed methods were extensively validated according to USP 27 requirements and ICH guidelines. The methods were applied to the analysis of pharmaceutical dosage forms containing binary mixtures of enalapril–lercanidipine and enalapril–nitrendipine. Moreover, the proposed methods were applied for the degradation studies of the selected compounds. Degradation studies were conducted using stress conditions such as UV light, acidic and alkaline hydrolysis, oxidation and heat in oven, to evaluate the ability of the separation of the response of standard compounds from their degradation products.     

Thermally loaded thick-walled cylindrically curved aluminum/steel-FGM-panel

Subject of the investigation is a thick-walled cylindrically curved shell guided at the ends which is heated at its inner or outer surface. The material is presupposed to be functionally graded obeying a power law. Both the elastic limits according to von Mises and the stress distributions for different grading exponents are discussed. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of bis[N-(2-fluoro-3-methoxy)-salicylideneaminato]copper(II)

The title compound, bis[N-(2-fluoro-3-methoxy)-salicylideneaminato]copper(II) [Cu(C₁₄H₁₂O₂FN)₂] was synthesized and its crystal structure was determined. The title compound is triclinic, space group P with a = 8.552(1), b = 9.645(1), c = 7.871(1) Å, = 108.708(1), = 93.769(1), = 79.429(1), V = 1208.98(1) ų, Z = 2, D _c = 1.696 gcm_–3, (Mo K) = 1.815 mm^–1, R = 0.0369 for 2963 reflections [I>2(I)]. The title compound has crystallographic inversion symmetry with two bidentate Schiff base ligand coordinated to the Cu atom in a square-planar arrangement. The Cu–N1 and Cu–O2 distances are 1.995(1) and 1.885(1) Å, respectively.