Biosorption of heavy metals on Aspergillus fumigatus immobilized Diaion HP-2MG resin for their atomic absorption spectrometric determinations

A solid phase extraction procedure based on biosorption of copper(II), lead(II), zinc(II), iron(III), nickel(II) and cobalt(II) ions on Aspergillus fumigatus immobilized Diaion HP-2MG has been investigated. The analytical conditions including amounts of A. fumigatus, eluent type, flow rates of sample and eluent solutions were examined. Good recoveries were obtained to the spiked natural waters. The influences of the concomitant ions on the retentions of the analytes were also examined. The detection limits (3sigma, N = 11) were 0.30 μg l⁻¹ for copper, 0.32 μg l⁻¹ for iron, 0.41 μg l⁻¹ for zinc, 0.52 μg l⁻¹ for lead, 0.59 μg l⁻¹ for nickel and 0.72 μg l⁻¹ for cobalt. The relative standard deviations of the procedure were below 7%. The validation of the presented procedure is performed by the analysis of three standard reference materials (NRCC-SLRS 4 Riverine Water, SRM 1515 Apple leaves and GBW 07605 Tea). The procedure was successfully applied for the determination of analyte ions in natural waters microwave digested samples including street dust, tomato paste, black tea, etc.     

Reply to the “Commentary by D. Collin & P. Martinoty”

We would like to thank the authors of the commentary [1] for their efforts to reproduce in the range of the narrow gap geometry (10–40 μm), our experiments [2] using the same polymer (PBuA – poly(n-butyl acrylate) – for the ordinary polymer) and a cyano-biphenyl substituted polyacrylate for the liquid crystal polymer sample. The comparison of their results with ours is very instructive.     

Determination of the optimum conditions for the synthesis of praseodymium(III) chloride

In the present work, we have synthesized praseodymium(III) chloride, PrCl₃, from the praseodymium oxide, Pr₆O₁₁, by dry method in the presence of ammonium chloride, NH₄Cl. This study includes the establishment of an assembly synthesis under inert gas. The thermal decomposing process of pure NH₄Cl was investigated by TG–DTG. The results showed that NH₄Cl begins to lose weight at 188 °C, large loss of weight ending at 302 °C when NH₄Cl is heated at the rate of 10 °C/min under N₂ atmosphere. For chlorination, NH₄Cl participates directly in the reaction, and HCl decomposed from NH₄Cl also contributes to the chlorination reaction. The influence of various synthesis parameters (temperature, contact time and chemical composition) on the reaction yield was studied, and the optimum conditions for synthesis were, thus, determined and discussed.     

Identification of Gel-Like Behaviour in Side-Chain Liquid Crystal Polymer Melts

We show through extensive rheological studies that Side-Chain Liquid Crystalline Polymer melts reveal an unexpected and surprising strong elasticity instead of a classical flow behaviour. Neutron Scattering experiments demonstrate that this elastic plateau cannot be correlated to the long range order of the nematic phase.     

Arsenic speciation in natural water samples by coprecipitation-hydride generation atomic absorption spectrometry combination

A speciation procedure for As(III) and As(V) ions in environmental samples has been presented. As(V) was quantitatively recovered on aluminum hydroxide precipitate. After oxidation of As(III) by using dilute KMnO₄, the developed coprecipitation was applied to determination of total arsenic. Arsenic(III) was calculated as the difference between the total arsenic content and As(V) content. The determination of arsenic levels was performed by hydride generation atomic absorption spectrometry (HG-AAS). The analytical conditions for the quantitative recoveries of As(V) including pH, amount of aluminum as carrier element and sample volume, etc. on the presented coprecipitation system were investigated. The effects of some alkaline, earth alkaline, metal ions and also some anions were also examined. Preconcentration factor was calculated as 25. The detection limits (LOD) based on three times sigma of the blank (N: 21) for As(V) was 0.012 μg L⁻¹. The satisfactory results for the analysis of arsenic in NIST SRM 2711 Montana soil and LGC 6010 Hard drinking water certified reference materials for the validation of the method was obtained. The presented procedure was successfully applied to real samples including natural waters for arsenic speciation.     

Solid-like rheological response of non-entangled polymers in the molten state

We show that non-entangled polymers display an elastic-like behaviour at a macroscopic scale (probed at some 0.100 mm thickness) up to at least hundred degrees above the glass transition temperature. This observation, found under non-slippage conditions, both for side-chain liquid crystalline polymers and ordinary polymers, is in contradiction with the typically found flow behaviour of polymer melt. Our measurements were carried out with a conventional rheometer at thicknesses of several tenths millimetres. Thus, we were probing bulk properties. The observed elasticity supposedly implies that even in the melt the chains experience a cohesive effect of macroscopic distances, involving collective motions over time scales longer than the individual relaxation time of an individual polymer chain. The detection of such a solid-like property of molten non-entangled polymers is of considerable importance for a better understanding of the polymer dynamics.     

The frozen state in the liquid phase of side-chain liquid-crystal polymers

Quenched isotropic melts of side-chain liquid-crystal polymers reveal surprisingly an anisotropic polymer conformation. This small-angle neutron-scattering (SANS) result is consistent with the identification of a macroscopic, solidlike response in the isotropic phase. Both experiments (rheology and SANS) indicate that the polymer system appears frozen on millimeter length scales and at the time scales of the observation. This result implies that the flow behavior is not the terminal behavior and that cross-links or entanglements are not a necessary condition to provide elasticity in melts.     

New Light on Old Wisdoms on Molten Polymers: Conformation,Slippage and Shear Banding in Sheared Entangled and Unentangled Melts

The flow of viscoelastic materials is usually interpreted as resulting from intramolecular properties. Typically, the non‐linear flow behaviour and sluggish relaxation dynamics in entangled polymers are interpreted by a disentanglement process. This molecular interpretation has never been validated by direct observation. We report here on in situ observations of polymer melts under steady‐state shear flow using neutron scattering and particle tracking velocimetry. It is shown that the chains remain largely undeformed under steady‐state shear flow whereas wall slippage and shear‐banding are identified in both entangled and unentangled polymer melts. These observations are of prime importance; they reveal that the flow mechanism and its viscoelastic signature reflect a collective effect and not properties of individual chains.