Determination of ultra traces of lead in water samples after combined solid-phase extraction–dispersive liquid–liquid microextraction by graphite furnace atomic absorption spectrometry

A solid-phase extraction coupled with dispersive liquid–liquid microextraction (DLLME) method followed by graphite furnace atomic absorption spectrometry (GFAAS) was developed for the extraction, preconcentration, and determination of ultra trace amounts of lead in water samples. Variables affecting the performance of both steps were thoroughly investigated. Under optimized conditions, 100 mL of lead solution were first concentrated using a solid phase sorbent. The extracts were collected in 1.50 mL of THF and 18 μL of carbon tetrachloride was dissolved in the collecting solvent. Then 5.0 mL pure water was injected rapidly into the mixture of THF and carbon tetrachloride for DLLME, followed by GFAAS determination of lead. The analytical figures of merit of method developed were determined. With an enrichment factor of 1,800, a linear calibration of 3–60 ng L^?1 and a limit of detection of 1.0 ng L^?1 were obtained. The relative standard deviation for seven replicate measurements of 30 ng L^?1 of lead was 5.2 %. The relative recoveries of lead in mineral, tap, well, and river water samples at spiking level of 10 and 20 ng L^?1 are in the range 94–106 %.     

A Cleavable Crosslinking Strategy for Commodity Polymer Functionalization and Generation of Reprocessable Thermosets

Covalently crosslinked polymeric materials, known as thermosets, possess enhanced mechanical strength and thermal stability relative to the corresponding uncrosslinked thermoplastics. However, the presence of covalent inter-chain crosslinks that makes thermosets so attractive is precisely what makes them so difficult to reprocess and recycle. Here, we demonstrate the introduction of chemically cleavable groups into a bis-diazirine crosslinker. Application of this cleavable crosslinker reagent to commercial low-functionality polyolefins (or to a small-molecule model) results in the rapid, efficient introduction of molecular crosslinks that can be uncoupled by specific chemical inputs. These proof-of-concept findings provide one potential strategy for circularization of the thermoplastic/thermoset plastics economy, and may allow crosslinked polyolefins to be manufactured, used, reprocessed, and re-used without losing value. As an added benefit, the method allows the ready introduction of functionality into non-functionalized commodity polymers.     

Interface,morphology, and the rheological properties of polymethylmethacrylate/impact modifier blends

Impact modifiers with grafted PMMA shell are used to modify polymethylmethacrylate matrix. The composition of the shell is chosen to enhance the interactions at the modifier/matrix interface and to obtain good dispersion of the impact modifier in order to optimize impact strength of the blend. The degree of interactions at the interface is characterized by the interfacial region where the chains of the matrix mix with those of the shell of the modifier. The deviation of the measured viscoelastic behavior of these blends from that predicted by the emulsion models has been attributed to the formation of the network structure due to the association of matrix chains with the shell of the modifier. It is expected that the network structure will decrease with increasing frequency and, as such, the effective volume of the particle is frequency dependent. This study uses the emulsion models to estimate the larger effective volume of the particle and, therefore, the extent of interaction at the interface. In the blends of this study it can be shown that at low modifier levels the solvent swelling of the modifier shell results in stronger interactions with the matrix; this effect is negated by the aggregation of particles at higher modifier loadings. The interaction of core modifier with the PMMA matrix seems to be similar to that of the core-shell modifier. This would not be expected from the calculated interfacial thickness of approximately 4 nm. It is, therefore, proposed that during melt-processing the core modifier surface was altered due to grafting of the matrix PMMA chains during melt-blending to (BA/St) copolymer of the core modifier thus reducing the interfacial tension. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2623–2634, 1998     

Current Scenario and Future Prospective of Ionic-Liquid Doped Polymer Electrolyte for Energy Application

Solid polymer electrolyte (SPE) films based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) with salt and ionic-liquid (IL) are synthesized using the solution-cast technique and summarized in this review. Doping ILs or salts increases ionic conductivity up to the device level. This is further confirmed using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements. Polarized optical microscopy (POM) affirms that enhancement in ionic conductivity is due to increase in amorphous nature of film. The complex nature of polymer electrolyte films is confirmed using Fourier transform infrared (FT-IR) spectroscopy. Overall results show that doping IL into polyether matrix is advantageous material playing a dominant role in electrochemical devices.     

ChemInform Abstract: First Principles Calculations of Electronic Structure and Magnetic Properties of Cr‐Based Magnetic Semiconductors Al1‐xCrxX (X: N,P, As,Sb).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Control of Quantum-Memory Induced by Generated Thermal XYZ-Heisenberg Entanglement: y-Component DM Interaction

This study explores the thermal quantum-memory-assisted entropic uncertainty relation (QM-EUR) and entanglement in a general two-qubit XYZ-Heisenberg spin chain model in the presence of the Dzyaloshinskii–Moriya (DM) interaction. The characterization of y-component DM and spin–spin interactions are particularly focused. It is found that the DM and spin–spin interaction strengths highly regulate the flow behavior and the initial final levels of QM-EUR and entanglement. In comparison, the spin–spin interaction strength in the z-direction remains useful in both ferromagnetic and anti-ferromagnetic regimes for entropic uncertainty suppression and entanglement generation. Additionally, the negative and the positive $y\mathrm{-}$directed DM values can usefully turn classical states into resourceful quantum states. The dynamics of thermal QM-EUR and entanglement-of-formation have symmetric behaviors only with respect to y-component DM and z-component spin–spin interaction. Finally, different critical points of temperature, $y\mathrm{-}$component DM as well as spin–spin interaction are encountered, which should be opted to preserve quantum correlations and degrade uncertainty.