Highly sensitive and selective sensing platform based on π–π interaction between tricyclic aromatic hydrocarbons with thionine–graphene composite

We are just beginning to exploit the fascinating potential of thionine, called electrochemical probe that can selectively recognize specific polycyclic aromatic hydrocarbons (PAHs), as tools for the detection of tricyclic aromatic hydrocarbons phenanthrene (PHE) and anthracene (ANT). A novel electrochemical sensing platform by modification of electroactive thionine functionalized graphene onto glass carbon electrode (Th/GRs/GCE) surface was constructed. The immobilized thionine showed a remarkable stability, which may benefit from the π–π stacking force with graphene. Under optimum conditions, the proposed electrochemical sensor exhibited high sensitivity and low detection limit for detecting PHE and ANT. The total amount of PHE and ANT could be quantified in a wide range of 10 pM–0.1 μM with a good linearity (R² = 0.9979) and a low detection limit of 0.1 pM (S/N = 3). Compounds which possess one or two benzene rings or PAHs with more than three rings, such as benzene, naphthalene (NAP), benzo[a]pyrene (BaP) and pyrene (PYR) show little interference on the detection. Consequently, a simple and sensitive electrochemical method was proposed for the determination of PHE and ANT, which was used to determine PHE and ANT in waste water samples. The electrochemical method provides a general tool that complements the commonly used spectroscopic methods and immune method for the detection of PAHs.     

A review on preparative and semi-preparative offgel electrophoresis for multidimensional protein/peptide assessment

Mass spectrometry (MS) techniques are commonly used for protein identification and further analysis of selected protein spots after high resolution 2-D electrophoresis. Complementary gel-free approaches have been developed during the last few years and have shown to be useful tools in modern proteomics. The development and application of various gel-free electrophoresis devices for performing protein fractionation according to the pI differences is therefore a topic of interest. This review describes the current state of isoelectric focusing (IEF) gel-free electrophoresis based on the Agilent offgel 3100 fractionator. The review includes, therefore, (i) an overview on IEF as well as other previous IEF gel-free electrophoresis developments; (ii) offgel fundamentals and future trends; (iii) advantages and disadvantages of current offgel procedures; (iv) requirements of isolated protein pellets for further offgel fractionation; (v) offgel fraction requirements to perform the second dimensional analysis by advance electrophoresis and chromatographic techniques; and (vi) effect of the offgel operating conditions on the stability of metal–protein complexes.     

Rational strategy for characterization of nanoscale particles by asymmetric-flow field flow fractionation: A tutorial

This tutorial proposes a comprehensive and rational measurement strategy that provides specific guidance for the application of asymmetric-flow field flow fractionation (A4F) to the size-dependent separation and characterization of nanoscale particles (NPs) dispersed in aqueous media. A range of fractionation conditions are considered, and challenging applications, including industrially relevant materials (e.g., metal NPs, asymmetric NPs), are utilized in order to validate and illustrate this approach. We demonstrate that optimization is material dependent and that polystyrene NPs, widely used as a reference standard for retention calibration in A4F, in fact represent a class of materials with unique selectivity, recovery and optimal conditions for fractionation; thus use of these standards to calibrate retention for other materials must be validated a posteriori. We discuss the use and relevance of different detection modalities that can potentially yield multi-dimensional and complementary information on NP systems. We illustrate the fractionation of atomically precise nanoclusters, which are the lower limit of the nanoscale regime. Conversely, we address the upper size limit for normal mode elution in A4F. The protocol for A4F fractionation, including the methods described in the present work is proposed as a standardized strategy to realize interlaboratory comparability and to facilitate the selection and validation of material-specific measurement parameters and conditions. It is intended for both novice and advanced users of this measurement technology.     

Combined chemical and phase equilibrium for the hydration of ethylene to ethanol calculated by means of the Peng-Robinson-Stryjek-Vera equation of state and the Wong-Sandler mixing rules

Due to the economics of the ethylene market and the subsidized production of fermentation-based ethanol in some countries, use of the ethylene hydration process to make ethanol has been steadily declining. The economics of this process might improve by combining the reaction and separation in a reactive distillation column, whose conceptual design requires a study of the combined chemical and phase equilibrium (CPE) of the reacting system. In this work, the Peng-Robinson-Stryjek-Vera equation of state was combined with the UNIQUAC activity coefficient model through the Wong-Sandler (WS) mixing rules in order to correlate the available experimental data for the vapor-liquid equilibria (VLE) of the ethylene-water, ethylene-ethanol, and ethanol-water binary systems at 200 °C. The interaction energies of the UNIQUAC model and the binary interaction coefficient of the WS mixing rules were used as the fitting parameters. From the optimum values of these parameters, both the VLE and the combined CPE of the ethylene-water-ethanol ternary system were predicted at 200 °C and various pressures. At this temperature, the catalytic activity of a H-pentasil zeolite has already been reported to exhibit a maximum for ethylene hydration, and also the experimentally measured two-phase region of the ternary system is sufficiently wide. By means of the reactive flash method, the chemical equilibrium compositions of the liquid and vapor phases were determined for several pressures, and the equilibrium conversion and the vapor fraction were calculated as functions of the ethylene to water feed mole ratio. It turns out that the vapor-liquid mixed-phase hydration of ethylene achieves equilibrium conversions much higher than those computed for a vapor-phase reaction that would hypothetically occur at the same conditions of pressure and feed mole ratio. It was found that the reactive phase diagram of the ternary system exhibits a critical point at 200 °C and 155 atm.     

Binuclear zinc(II) complexes with the anti-inflammatory compounds salicylaldehyde semicarbazone and salicylaldehyde-4-chlorobenzoyl hydrazone (H2LASSBio-1064)

Complexes [Zn₂(HL¹)₂(CH₃COO)₂] (1) and [Zn₂(L²)₂] (2) were synthesized with salicylaldehyde semicarbazone (H₂L¹) and salicylaldehyde-4-chlorobenzoyl hydrazone (H₂LASSBio-1064, H₂L²), respectively. The crystal structure of (1) was determined. Upon recrystallization of previously prepared [Zn₂(HL²)₂(Cl)₂] (3) in 1:9 DMSO:acetone crystals of [Zn₂(L²)₂(H₂O)₂]·[Zn₂(L²)₂(DMSO)₄] (3a) were obtained. The crystal structure of 3a was also determined. All crystal structures revealed the presence of phenoxo-bridged binuclear zinc(II) complexes.     

Noisy colored point set matching

We propose a process for determining approximated matches, in terms of the bottleneck distance, under color preserving rigid motions, between two colored point sets A,B∈R², |A|≤|B|. We solve the matching problem by generating all representative motions that bring A close to a subset B^′ of set B and then using a graph matching algorithm. We also present an approximate matching algorithm with improved computational time. In order to get better running times for both algorithms we present a lossless filtering preprocessing step. By using it, we determine some candidate zones which are regions that contain a subset S of B such that A may match one or more subsets B^′ of S. Then, we solve the matching problem between A and every candidate zone. Experimental results using both synthetic and real data are reported to prove the effectiveness of the proposed approach.