On the determination of HCl+ (A,v′) vibrational populations from HCl+ (A→X) fluorescence spectra: direct comparison between photoionization and penning ionization

Using a beam apparatus, we have measured the HCl⁺ (A,v′→X,v″) fluorescence spectra of HCl⁺ (A,v′) ions formed in HeI (58.4 nm), and NeI (73.6 nm) photoionization and, for the first time, in He (2³ S) Penning ionization under single collision conditions with a wavelength bandwidth around 1 nm. In addition, we have studied Ne (3s ³ P _{2, 0}) Penning ionization of HCl at three different collision energies. The procedure and the problems in extracting HCl⁺ (A,v′) vibrational populations from the data are discussed in some detail. Thedirect comparison of photoionization and Penning ionization data allows definitive conclusions to be drawn on the question whether final state interactions in the Penning reaction change the “nascent” vibrational population (determined by electron spectrometry); for He (2³ S)+HCl, such changes are shown to be absent within the experimental uncertainty (<±10%). For Ne (3s ³ P _{2, 0})+HCl, the HCl⁺ (A,v′=0, 1) populations are also found to be close to those measured by electron spectrometry and essentially independent of collision energy in the range 34–96 meV. From measurements of the fluorescence intensity as a function of HCl density, we have evidence for a fast loss of HCl⁺ (A,v′) ions in collisions with HCl (rate constant around 5·10^?9 cm³s^?1).     

A sensor based on incorporating Ni2+ into ZnO nanoparticles-multi wall carbon nanotubes-poly methyl metacrylat nanocomposite film modified carbon paste electrode for determination of carbohydrates

The ZnO nanoparticles (ZnONPs) were synthesized with gelatin as stabilizer via the sol-gel method and were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). An electrochemical sensor based on ZnO nanoparticles-multi wall carbon nanotubes-poly methyl metacrylat (ZnONPs-MWCNT-PMMA) composite film was developed by incorporating Ni²⁺ into the ZnONPs-MWCNT-PMMA film modified carbon paste electrode (Ni²⁺/ZnONPs-MWCNT-PMMA/CPE). The electrochemical activity of Ni²⁺/ZnONPs-MWCNT-PMMA/CPE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni²⁺/ZnONPs-MWCNT-PMMA/CPE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. Ni²⁺/ZnONPs-MWCNT-PMMA/CPE also show good electrocatalytic activity toward the oxidation of carbohydrates (glucose, fructose and sorbitol). The Ni²⁺/ZnONPs-MWCNT-PMMA/CPE gives a good linear range with a detection limit of 8, 6, and 9 μM towards the determination of glucose, fructose and sorbitol, respectively by amperometry. Furthermore, the modified sensor was successfully applied to the sensitive determination of carbohydrates in real samples.     

Effect of Cl substituent in the aromatic tetracycline ring on its reactivity with solvated electrons

Decomposition yields of tetracycline hydrochloride /TC.HCl/ and chlorotetracycline hydrochloride /ClTC?HCl/ in methanol solution saturated with Ar or N₂O were determined. Rate constants of the reaction e_s with some antibiotics were obtained: $$\begin{gathered} k/e_s^ - + ClTC \cdot HCl/ = 2 \cdot 49 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} ; \hfill \\ k/e_s^ - + TC \cdot HCl/ = 2 \cdot 86 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} \cdot \hfill \\ \end{gathered} $$ On the basis of the diffence between decomposition yields: ΔG=G_?TC.HCl^?G?ClTC.HCl′ 7-C?Cl group decomposition yield and the rate constant $$k/e_s^ - + Cl - C - 7/ = 7 \cdot 94 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} $$ were determined. It was demonstrated by¹H NMR that the radical formed by degradation of 7-C?Cl group is recombined with the H atoms leading to ClTC.HCl being converted into tetracycline hydrochloride /TC.HCl/.     

Solute-solvent interactions in acid-base dissociation: nine protonated nitrogen bases in water-DMSO solvents

A titration method utilizing glass electrodes and silver-silver chloride electrodes in a cell without liquid junction has been used to determine the acidic dissociation constants at 15, 25, and 35°C of nine protonated nitrogen bases in mixtures of water and dimethyl sulfoxide (DMSO). The mole fraction of DMSO in the mixed solvents was 0.2, 0.4, 0.6, and 0.8. The cell was calibrated with HCl (molality=0.01 mole-kg^?1) in the mixed solvents, and the ionic strength and chloride molality remained substantially unchanged during the titration with added base. This method minimizes the errors resulting from the formation of AgCl ₂ ^? in the media rich in DMSO. The pK _a of all the protonated bases passes through a minimum at a solvent composition close to that at which H₂O-DMSO mixtures display a maximum solvent structure. The results are discussed in terms of the preferential solvation of ions by the two types of solvent molecules. They are consistent with the hypothesis that increased solvent structure is accompanied by increased desolvation of the cation acids.     

Thermal decomposition of polymethylmethacrylate synthesized with anionic catalysts

TG and DTA data are used to show that the thermal decomposition of polymethylmethacrylate (PMMA) synthesized with anionic catalysts depends on the nature of the catalyst. It is found that the thermal stability of PMMA obtained by using anionic amide catalysts is higher than that of radical PMMA and of PMMA obtained with other anionic catalysts, and depends on the temperature of polymerization and on the molecular weight of the polymer.     

A novel high efficiency benzophenone based polymeric photoinitiator from ring-opening polymerization of benzoxazine

A novel polymeric photoinitiator based on benzoxazine was synthesized by introducing 4-hydroxy benzophenone, diglycolamine and paraformaldehyde into the macromolecular chain. Its molecular structure was characterized by ¹H NMR, FTIR, and UV-Vis spectroscopy. Photopolymerization of tripropylene glycol diacrylate and trimethylolpropane triacrylate initiated by polybenzoxazine, benzoxazine, and benzophenone was studied by real time FTIR spectroscopy. The results obtained are discussed.     

Electron attachment to HCl clusters

Negatively charged cluster ions of hydrogen chloride are formed by electron attachment to HCl clusters, which are produced in a seeded supersonic beam traversing a sustained gas discharge. Cluster ions of (HCl) _n ^? , withn=2, and tentatively withn=3 and 4 are observed. Cluster ions like Cl _n ^? , Cl _n ^? (HCl) _m , and withAr attached to them are also seen. The relevance to radiation chemistry of HCl if briefly discussed. Atoms evaporating from the hot, thoriated tungsten filament of the glow discharge lead to clusters such as Th _n ^? and its oxides.     

In Situ Characterization of Proteins Using Laserspray Ionization on a High-Performance MALDI-LTQ-Orbitrap Mass Spectrometer

The MALDI-LTQ-Orbitrap XL mass spectrometer is a high performance instrument capable of high resolution and accurate mass (HRAM) measurements. The maximum m/z of 4000 precludes the MALDI analysis of proteins without generating multiply charged ions. Herein, we present the study of HRAM laserspray ionization mass spectrometry (MS) with MS/MS and MS imaging capabilities using 2-nitrophloroglucinol (2-NPG) as matrix on a MALDI-LTQ-Orbitrap XL mass spectrometer. The optimized conditions for multiply charged ion production have been determined and applied to tissue profiling and imaging. Biomolecules as large as 15 kDa have been detected with up to five positive charges at 100 K mass resolution (at m/z 400). More importantly, MS/MS and protein identification on multiply charged precursor ions from both standards and tissue samples have been achieved for the first time with an intermediate-pressure source. The initial results reported in this study highlight potential utilities of laserspray ionization MS analysis for simultaneous in situ protein identification, visualization, and characterization from complex tissue samples on a commercially available HRAM MALDI MS system. Graphical Abstract

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Development of novel sol–gel coatings by chemically bonded ionic liquids for stir bar sorptive extraction—application for the determination of NSAIDS in real samples

In this work, a novel ionic liquid (IL) chemically bonded sol–gel coating was prepared for stir bar sorptive extraction (SBSE) of nonsteroidal anti-inflammatory drugs (NSAIDs) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). By using γ-(methacryloxypropyl)trimethoxysilane (KH-570) as a bridging agent, 1-allylimidazolium tetrafluoroborate ([AIM][BF₄]) was chemically bonded onto the bare stir bar, and the prepared IL-bonded sol–gel stir bar coating showed higher extraction efficiency and better adsorption/desorption kinetics for target NSAIDs over other polydimethylsiloxane (PDMS)-based or monolithic stir bar coatings. The mechanical strength and durability (chemical/thermal stability) of the prepared IL-bonded sol–gel coating were excellent. The influencing factors of SBSE, such as sample pH, salt effect, stirring rate, extraction time, desorption solvent, and desorption time, were optimized, and the analytical performance of the developed SBSE-HPLC-UV method was evaluated under the optimized conditions. The limits of detection (LODs) of the proposed method for three NSAIDs were in the range of 0.23–0.31 μg L^?1, and the enrichment factors (EFs) were in the range of 51.6–56.3 (theoretical enrichment factor was 100). The reproducibility was also investigated at concentrations of 5, 20, and 100 μg L^?1, and the relative standard deviations (RSDs) were found to be less than 9.5, 7.5, and 7.6 %, respectively. The proposed method was successfully applied for the determination of NSAIDs in environmental water, urine, and milk samples. Graphical Abstract

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Detection of trace levels of atrazine using surface-enhanced Raman scattering and information visualization

The detection of trace amounts of pesticides is essential for the quality control of waters, particularly with their inevitable increasing use with the growing demand for food. In this study, we report on the detection of atrazine, a highly toxic herbicide, down to 5?×?10^?12 M, which is sufficient to monitor the quality of drinking water even according to the most stringent international regulations. Such detection was performed with surface-enhanced Raman scattering (SERS) in atrazine incorporated into silver nanoparticles (AgNPs) colloids, with the SERS spectra being treated with Sammon’s mapping, an information visualization technique. In addition to providing a fingerprint of the atrazine molecules, SERS is advantageous in comparison with impedance spectroscopy and cyclic voltammetry applied to a sensor array of units made with layer-by-layer (LbL) films containing AgNPs and AuNPs. The combined use of SERS and information visualization methods is promising for monitoring water quality with regard to other pesticides, which may even approach single molecule detection.     

Angular dependent post-collision interaction in auger processes

We have reformulated the theory of post-collision interaction (PCI) for Auger-decay following inner-shell photoionisation in order to take the time into account with the Auger-electron need to overtake the slow electron. The energy-shift of the Auger-electron due to PCI is calculated by solving in a reasonable approximation the classical equation of motion for the Auger electron. In contrast to the theory of Russek and Mehlhorn we derive analytical expressions for the transition amplitude, the line shape and the line shift of the Auger-electrons. If in our model the Auger electron and the slow electron are treated uncorrelated in direction our analytical expressions agree well with the numerical results of Russek and Mehlhorn. However if we account for directional electron-electron correlations, we show that deviations from the theory of Russek and Mehlhorn are to be expected. The possibility of detecting these deviations is discussed.     

Organelle sensor: amperometric determination of nadh by immobilized mitochondrial electron transport particles

A new sensor for NADH was developed by making use of an immobilized subcellular organelle. Mitochondria was used as a model system for assembling an organelle sensor. Mitochondrial electron transport particles (ETP) were prepared from beef heart muscle and entrapped in the membrane formed of agar gel. The membrane-bound ETP was found capable of NADH oxidation: $$NADH + \tfrac{1}{2}O_2 + H^ + \xrightarrow{{ETP}}NAD^ - + H_2 O$$ The membrane was tightly attached to the surface of an oxygen electrode capable of amperometric detection of O2. The sensor responded to NADH in solution with a resulting electric output. The response was enhanced by the addition of 2,4-dinitrophenol (DNP). NADH was determined in the concentration range 1–300 µM. NADH was alternatively determined for 2 weeks without replacing the ETP-bound membrane.     

Extraction and chemical investigation of jute (Corchorus olitorius,Linn.) seed protein

Studies were made on the protein solubility of deoiled jute (Corchorus olitorius, Linn.) seed in aqueous solution over various pHs and in different concentrations of NaCl at pH 8.0. Chemical analysis of the seed protein showed 16 amino acids, of which 9 were essential. Gel filtration on Sephadex G-200 revealed the presence of four components, and their molecular weights were determined by two standard methods. Extractable jute seed proteins in salt solution were separated into six fractions electrophoretically (SDS-PAGE). The molecular weights of the six fractions were found to be 118,000; 103,000; 96,000; 67,500; 48,500; and 15,000.     

Stereoselective separation and pharmacokinetic dissipation of the chiral neonicotinoid sulfoxaflor in soil by ultraperformance convergence chromatography/tandem mass spectrometry

Ultraperformance convergence chromatography/tandem triple quadrupole mass spectrometry (UPC²-MS/MS) is a novel tool in separation science that combines the advantages of supercritical fluid chromatography with ultraperformance liquid chromatography/MS/MS technology. The use of nontoxic CO₂ fluid and a postcolumn additive to complement MS/MS allows better control of analyte retention for chiral separation and high-sensitivity determination with different chiral stationary phases. This paper reports the stereoselective separation and determination of the chiral neonicotinoid sulfoxaflor in vegetables and soil by UPC²-MS/MS. Baseline resolution (Rs?≥?1.56) of and high selectivity (LOQ?≤?1.83 μg/kg) for the four stereoisomers were achieved by postcolumn addition of 1 % formic acid–methanol to a Chiralpak IA-3 using CO₂/isopropanol/acetonitrile as the mobile phase at 40 °C, 2,500 psi, and for 6.5 min in electrospray ionization positive mode. Rearranged Van’t Hoff equations afforded the thermodynamic parameters ΔH ^ο and ΔS ^ο, which were analyzed to promote understanding of the enthalpy-driven separation of sulfoxaflor stereoisomers. The interday mean recovery, intraday repeatability, and interday reproducibility varied from 72.9 to 103.7 %, from 1.8 to 9.2 %, and from 3.1 to 9.4 %, respectively. The proposed method was used to study the pharmacokinetic dissipation of sulfoxaflor stereoisomers in soil under greenhouse conditions. The estimated half-life ranged from 5.59 to 6.03 d, and statistically nonsignificant enantioselective degradation was observed. This study not only demonstrates that the UPC²-MS/MS system is an efficient and sensitive method for sulfoxaflor stereoseparation, but also provides the first experimental evidence of the pharmacokinetic dissipation of sulfoxaflor stereoisomers in the environment. Graphical Abstract

Chemical structure and UPC²-MS/MS separation chromatogram of sulfoxaflor. (* stereogenic center)     

Melt miscibility of HDPE/UHMWPE,LDPE/UHMWPE,and LLDPE/UHMWPE blends detected by dynamic rheometer

The dynamic rheological behavior of high density polyethylene (HDPE)/ultrahigh molecular weight polyethylene (UHMWPE) blends, low density polyethylene (LDPE)/UHMWPE blends and linear low density polyethylene (LLDPE)/ UHMWPE blends was measured in parallel plate rheometer at 200°C. The analysis of log-additivity rule, Cole-Cole plots and Han curves of the three series blends indicated that the LDPE/UHMWPE blends were miscible in the melt, while the HDPE/UHMWPE blends and LLDPE/UHMWPE blends showed phase separation. The DSC results of LLDPE/UHMWPE blends and HDPE/UHMWPE blends were consistent with the rheological properties, while for the thermal properties of LDPE/UHMWPE blends, results revealed three endothermic peaks, which indicated a liquid-solid phase separation in LDPE/UHMWPE blends.     

Kinetics and possible mechanism of hydrogen chloride oxidation over supported copper-containing salt catalysts: I. Kinetics of HCl oxidation in the deacon and methane oxychlorination reactions over a copper-potassium salt catalyst

The kinetics of HCl oxidation at 350–425°C over a (CuCl₂-KCl)/support catalyst in two complementary processes—Deacon and methane oxychlorination reactions—has been investigated using a gradientless technique. This has allowed the range of \(P_{Cl_2 }\) in the reaction mixture to be markedly extended. New kinetic features of HCl oxidation under conditions such that this process does and does not depend on P _HCl have been discovered. The kinetic equations obtained in this study fit experimental data in a wider range of conditions than the equations proposed earlier. The results of this study suggest the existence of two HCl oxidation pathways in the Deacon reaction.     

Carbon nanotubes induced poly(vinylidene fluoride) crystallization from a miscible poly(vinylidene fluoride)/poly(methyl methacrylate) blend

Different contents of carbon nanotubes (CNTs) were introduced into a miscible poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend. The interfacial affinity between CNTs and components of the blend was evaluated by calculating the interfacial tension. The dispersion and microstructure of CNTs in the nanocomposites were investigated through scanning electron microscope and rheological measurement. The effect of CNTs on the crystallization of PVDF was comparatively investigated through nonisothermal and isothermal crystallization processes. The results showed that CNTs exhibited stronger interfacial affinity to PMMA. Homogeneous dispersion of CNTs in the nanocomposites was achieved. Largely enhanced crystallization temperature and increased crystallinity of PVDF were obtained by adding CNTs during the nonisothermal crystallization process. The results obtained from the isothermal crystallization process proved that CNTs induced the concentration fluctuation in the sample, which resulted in the formation of spherulites with different types, i.e., the banded spherulites and compact spherulites. Furthermore, both the crystallization temperature and the content of CNTs exhibited great influence on the crystalline morphology of PVDF.     

Properties of human parotid amylase immobilized by covalent binding to glass or sepharose or by reaction with immobilized antibody

Human parotid amylase was immobilized by covalent binding to CNBr-activated Sepharose, to Corning GAO-3940 silica glass biomaterial support by the diazonium reaction or reaction with glutaraldehyde, or as a result of the antigen-antibody reaction between rabbit antihuman parotid amylase IgG that was covalently bonded to GAO glass and soluble amylase. The amylase directly bonded to the supports showed constant activity at flow rates of 3-15 ml/min through a 1.76-cm³ (8-mm diameter) support bed, did not lose enzyme into a circulating starch solution, retained its activity in the presence of soluble antiamylase IgG, was optimally active at 35°-40°C, and lost activity at 40°-45°C. When the enzyme was bound by interaction with immobilized antibody, full activity was expressed, but some enzyme was solubilized by a circulating starch solution. Immobilization of either amylase or antiamylase IgG makes dissolution of the antigen-antibody bond difficult.     

Interaction of radium with freshwater sediments and their mineral components

Radiotracer method has been used for investigation of the adsorption and desorption of traces of radium on muscovite and feldspar (albite) under conditions similar to those prevailing in waste and surface waters. The effects of pH, liquid to solid ratio, time, ionic strength (Na⁺) and presence of Ca²⁺ or SO ₄ ^2? ions have been studied. It has been concluded that both minerals can significantly affect the fate and migration of radium in surface waters if present as major components of bottom sediments or as suspended solids in concentrations of several milligrams per liter or higher. Muscovite can absorb radium even from moderately acidic waters. Radium adsorbed on muscovite and albite cannot be easily released upon an increase of the salinity of ambient water. However, almost complete desorption can be achieved with 1M HCl. Mechanisms of radium adsorption on both minerals and character of the adsorption sites are discussed.     

The IUPAC aqueous and non-aqueous experimental pKa data repositories of organic acids and bases

Accurate and well-curated experimental pKa data of organic acids and bases in both aqueous and non-aqueous media are invaluable in many areas of chemical research, including pharmaceutical, agrochemical, specialty chemical and property prediction research. In pharmaceutical research, pKa data are relevant in ligand design, protein binding, absorption, distribution, metabolism, elimination as well as solubility and dissolution rate. The pKa data compilations of the International Union of Pure and Applied Chemistry, originally in book form, have been carefully converted into computer-readable form, with value being added in the process, in the form of ionisation assignments and tautomer enumeration. These compilations offer a broad range of chemistry in both aqueous and non-aqueous media and the experimental conditions and original reference for all pKa determinations are supplied. The statistics for these compilations are presented and the utility of the computer-readable form of these compilations is examined in comparison to other pKa compilations. Finally, information is provided about how to access these databases.