Wide-bore glass capillary columns for gas chromatography. Their preparation and application

Summary Methods for the preparation of wide-bore glass capillary columns for gas chromatography are presented. The pretreatment of the columns (etching, carbonization, deactivation and/or surface-coating with porous materials), and the coating of them with polar or apolar phases (preferably by the static method) is described. The performance of the columns prepared is evaluated and a number of applications are given, such as analysis of volatile compounds, pesticides, lipids and GC/MS analysis. In some respects, the wide-bore glass capillaries have advantages over the narrow-bore types. They can be installed very easily in GC-instruments, and permit the analysis of larger samples. A system of collecting separated sub-g fractions in glass capillary traps, which makes direc re-injection from these traps possible, completes the methods presented.     

Super Oxygen and Improved Water Vapor Barrier of Polypropylene Film with Polyelectrolyte Multilayer Nanocoatings

Biaxially oriented polypropylene (BOPP) is widely used in packaging. Although its orientation increases mechanical strength and clarity, BOPP suffers from a high oxygen transmission rate (OTR). Multilayer thin films are deposited from water using layer‐by‐layer (LbL) assembly. Polyethylenimine (PEI) is combined with either poly(acrylic acid) (PAA) or vermiculite (VMT) clay to impart high oxygen barrier. A 30‐bilayer PEI/VMT nanocoating (226 nm thick) improves the OTR of 17.8 μm thick BOPP by more than 30X, rivaling most inorganic coatings. PEI/PAA multilayers achieve comparable barrier with only 12 bilayers due to greater thickness, but these films exhibit increased oxygen permeability at high humidity. The PEI/VMT coatings actually exhibit improved oxygen barrier at high humidity (and also improve moisture barrier by more than 40%). This high barrier BOPP meets the criteria for sensitive food and some electronics packaging applications. Additionally, this water‐based coating technology is cost effective and provides an opportunity to produce high barrier polypropylene film on an industrial scale.

     

Development of oxygen selective adsorbents for gas separation and purification

Development, characterization, and testing of oxygen selective chemical adsorbents (chemisorbents) for cyclic gas separation and purification applications using pressure cycling are described herein. Three structurally related compositions, designated IA-1, IA-2, and IA-3 offer high oxygen capacities and selectivities coupled with fast uptake kinetics. Extended lifetime tests for IA-3 indicate a half-life of 17 years with 0.01 % oxygen at 60 °F under cycling conditions. Hazard testing results are presented and these data impose some restrictions on handling and use. For practical applications using packed beds of adsorbent in pressure-swing cycles, agglomeration is required to produce larger particles using formulations and methods that minimize the impact on oxygen binding. Methods are described herein using polymeric binders that provide the necessary physical features while maintaining adequate adsorption performance characteristics. Proof of concept oxygen removal test results are also described.     

Influence of the Layer Morphology on the Electrical Properties of Sol Gel Transparent Conducting Oxide Coatings

Tranparent conducting coatings have been prepared by sol gel methods either by a conventional sol-gel process (Antimony doped Tin Oxide—ATO, Aluminium doped Zinc Oxide—AZO) or a new wet chemical process using fully dispersed crystalline nanoparticles (ATO, Indium Tin Oxide—ITO). The dip coating technique has been used as deposition technique with single coating thickness varying from a few nanometer to ca. 400 nm. The layers have been fired in a furnace. Structural properties have been determined by x-ray diffraction and TEM analysis and the electrical properties by the van der Pauw/Hall measurement. Three different coating procedures have been used to investigate the effect on the structure, morphology and the electrical properties of the coatings. It is shown that the individual layer thickness in multilayer coatings influences dramatically the mentioned properties. Very thin individual layers favour a heterogeneous nucleation with dense columnar growth of the crystallites leading to low electrical resistivity ( 10^–3 cm), while thick individual layers result in a porous morphology made of small crystallites leading to resistivities in the 10^–2 cm range.     

Defective α‐Fe2O3(0001): An ab Initio Study

By using density functional theory calculations at the PBE+U level, we investigated the properties of hematite (0001) surfaces decorated with adatoms/vacancies/substituents. For the most stable surface termination over a large range of oxygen chemical potentials (${\mu _{\rm{O}} }$ ), the vacancy formation and adsorption energies were determined as a function of ${\mu _{\rm{O}} }$ . Under oxygen‐rich conditions, all defects are metastable with respect to the ideal surface. Under oxygen‐poor conditions, O vacancies and Fe adatoms become stable. Under ambient conditions, all defects are metastable; in the bulk, O vacancies form more easily than Fe vacancies, whereas at the surface the opposite is true. All defects, that is, O and Fe vacancies, Fe and Al adatoms, and Al substituents, induce important modifications to the geometry of the surface in their vicinity. Dissociative adsorption of molecular oxygen is likely to be exothermic on surfaces with Fe/Al adatoms or O vacancies.     

Sol-Gel Preparation of Silica Films with Controlled Surface Morphology and Their Application to a Low Reflective Glass

Silica coating films with various surface morphologies, such as flat, porous (with deep pores), concave-convex (with hills and valleys), and convex (with hills on flat plane) structure were prepared from a mixture of two kinds of sols derived from polymerized tetraethoxy-silane (TEOS) and methyltriethoxysilane (MTES). Different surface morphologies were obtained by varying the molar ratio r = MTES/TEOS of the coating solution. The surface was flat for r less than 2.5, porous for 2.5 r < 5, concave-convex for 5 r < 7.5, convex for 7.5 r < 13, and again flat for r larger than 13. For 2.5 r < 5, the apparent refractive index of the silica film with porous morphology was decreased to 1.23 by selecting the solvent and by controlling the relative humidity of the coating atmosphere and the heat treatment temperature. Coating of glass with silica films of low refractive index of 1.23 led to the low reflective glasses with visible light reflectance Rvis of less than 0.2%.     

Application of luminescent nanocrystals as labels for biological molecules

Luminescent semiconductor nanocrystals, so called quantum dots (QD), have attracted increasing interest for bioanalytical labeling applications in recent years. This review describes the major optical and (bio)chemical features of this class of label, compared with organic dyes. Different conjugation methods are also discussed and the most important recent applications are presented. An overview over the current state-of-the-art is given, as also is an outlook on possibilities and limitations.     

Quantitative depth-profiling with GDOS: application to ZnNi-electrogalvanized steel sheets

Summary Studies are made on quantitative GDOS depth profile analysis for ZnNi-coatings. Relative and absolute depth resolution on the interface ZnNi-coating/steel substrate were evaluated in a thickness range of 0.5 to 5 m using two different anode tube diameters. For quantification, an improved approach of the model of constant emission yield was established. The results are demonstrated on ZnNi-electrodeposits with different coating thickness and chemical content.     

Low-energy electrons and X-ray irradiation effects on plasma-polymerized allylamine bioactive coatings for stents

Radiation used in biomedical applications causes chemical changes to biomedical materials. This work is an ex situ simulation of the influence of low-energy electron (LEE) impact and X-ray irradiation on the chemical properties of plasma-polymerized allylamine (PPA) bioactive and biocompatible stent coatings. Preliminary X-ray photoelectron spectroscopy (XPS) results show that PPA coatings oxidize in contact with ambient air by the detection of C-O and CO bonds which are typical of polymer oxidation. Chemical changes after LEE and X-ray irradiation are mainly a loss of oxygen, assuming a surface deoxidizing and not a complete destruction of the surface. XPS survey analyses show that the amine groups remain stable during irradiation. LEE impact measurements by TOF mass spectrometry show that the main ionic losses are H⁻ ions. It appears that CN groups are stable under irradiation and we observe a loss of hydrogen and oxygen as the main chemical modifications. In conclusion, these results suggest that PPA coatings are stable under biomedical radiation, and they can therefore be used for bioactive and biocompatible stent coatings.     

The study of catalysis by novel gas chromatographic techniques

Summary Studies of catalytic reactions have been made using differential (sample-vacancy) and stopped-flow gas chromatography. Reactions are often very sensitive to trace materials and in particular it has been necessary to devise a technique for removing oxygen from carrier-gas streams down to very low levels. The techniques and the results are often relevant to the more normal analytical applications of gas chromatography.Presented at Table Ronde sur les mesures physicochimiques par chromatographie en phase gazeuse (Lyons, November 13–14th, 1973), organized by Dr.robin (INSA, Villeurbanne)     

Preparation of Core/Shell Structure of α-Al(OH)3-SiO2 by Heterogeneous Nucleation-and-Growth Processing

In order to solve the difficult problem of heterogeneity of different components in the procedure of ceramic preparation, a novel processing (heterogeneous nucleation-and-growth processing) was used to prepare homogeneous distribution powders. Composite coating particles consisting of alpha aluminum hydroxide (-Al(OH)₃) cores (average particle size 0.42 m) with outer homogeneous amorphous silica layer are prepared by heterogeneous nucleation-and-growth processing. Effects of silica content in composite coating particles versus concentration of silicon tetraethoxide (TEOS), pH value, time and temperature are studied. The homogeneous amorphous silica layer on cores is confirmed by X-ray diffraction, transmission electron microscopy and zeta potential measurement.     

Nuclear Recoil Implosion for Generating Radioisotopically Labeled Fullerene Endohedrals and Cages

The use of nuclear recoil for producing radioactive endohedral and cage-labeled fullerenes is presented, with special emphasis on the energy of chemical effects after nuclear particle capture. The different possibilities using (n,), (n,), (p,n), (g,n) and (,n) and (,n) nuclear reactions are treated in detail.     

Abrasion resistant inorganic/organic coating materials prepared by the sol-gel method

Novel abrasion resistant coating materials prepared by the sol-gel method have been developed and applied on the polymeric substrates bisphenol-A polycarbonate and diallyl diglycol carbonate resin (CR-39). These coatings are inorganic/organic hybrid network materials synthesized from 3-isocyanatopropyltriethoxysilane functionalized organics and metal alkoxide. The organic components are 3,3-iminobispropylamine (IMPA), resorcinol (RSOL), diethylenetriamine (DETA), poly(ethyleneimine) (PEI), glycerol and a series of diols. The metal alkoxides are tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS). These materials are spin coated onto bisphenol-A polycarbonate and CR-39 sheets and thermally cured to obtain a transparent coating of a few microns in thickness. Following the curing, the abrasion resistance is measured and compared with an uncoated control. It was found that the abrasion resistance of inorganic/organic hybrid coatings in the neat form or containing metal alkoxide can be very effective to improve the abrasion resistance of polymeric substrates. The adhesion tests show that the adhesion between coating and substrate can be greatly improved by treating the polymeric substrate surface with a primer solution of isopropanol containing 3-aminopropyltriethoxysilane (3-APS). The interaction between 3-APS and the polycarbonate surface was investigated by a molecular dynamics simulation. The results strongly suggest that the hydrogen bonding between the amino group of the 3-APS and ester group in the polycarbonate backbone are sufficiently strong to influence the orientation of the primer molecules. The abrasion resistance of these new coating systems is discussed in light of the structure of the organic components. All of these results show that these coating materials have excellent abrasion resistance and have potential applications as coating materials for lenses and other polymeric products.     

NaX zeolite,carbon fibre and CaCl2 ammonia reactors for heat pumps and refrigerators

The key elements of solid sorption machines are the chemical compressors-adsorbers. Two categories of the solid sorption system are analyzed: adsorbents NaX zeolite, carbon fibre Busofit with NH₃, and complex combinations that undergo chemical reaction and physical adsorption (CaCl₂ + carbon fibre Busofit with NH₃).Two phase ammonia motion inside the adsorbent bed was checked. That accompanied NH₃/CaCl₂ solution redistribution between the cold and hot surfaces of the sorbent bed, resulting in a rich CaCl₂ concentration at the boundaries.Solid sorption heat pump and refrigerator technology utilizing heat pipe heat recovery with a condensing/evaporating refrigerant holds considerable promise for bivariant (space and domestic) applications due to the variable temperature and variable load capabilities of such machines.     

Sol-Gel Route and Characterization of Supported Perovskites for Membrane Application

In the last decades the sol-gel method has registered an intensive development in new fields of applications as membrane technologies, solid-state chemical sensors, SOFCs, etc. The aim of the present work is to make a bibliographic overview on the problem discussed and to develop supported perovskites for membranes application via sol-gel route and to study them. In this context a preparation procedure has been accomplished for deposition of mixed conducting La_0.8Sr_0.2Co_0.8Fe_0.2O_{3 –} thin layers on porous ceramic supports. Characterization techniques, as ESR control of Fe(III) ions into the precursor solutions, SEM surface morphology study, La- Sr- Co- and Fe-element distribution, as well as XPS partial spectra of La3d- Sr3d- Co2p- Fe2p and O1s- for a single coating surface have been applied. Adequate interpretation and conclusions regarding membranes investigated are presented as well.     

Synthesis,characterisation and ferric ion complexation studies of chelating probes for oxidative stress

The ferric ion binding characteristics of a novel chelating probe for detecting reactive oxygen and nitrogen species are reported. The probe comprises a polyaminocarboxylic acid chelator (EDTA) conjugated with aromatic amino acids. The probe (i) complexes redox-active and non-redox active metal ions and (ii) differentiates between different reactive oxygen/nitrogen species based upon the reaction products with same. The ferric ion binding characteristics were measured using species distribution and electronic absorption spectroscopic investigations. Over the physiological pH range a favoured one to one complex exists.     

Biomedical radioisotope generator systems

Although the⁹⁹Mo^99mTc radionuclide generator system has evolved as the workhorse of nuclear medicine over the past three decades, recent developments in radionuclide generator technology have provided positron emitters for PET studies, radionuclides for therapy, and ultra short-lived radionuclides for repeated clinical applications. Attention is being paid to development ofin vivo generator systems and potential use of tandem generator systems. Separation of radionuclides in a generator system exploits differences in chemical properties of the parent-daughter pair; information is presented for these generator types based on the three chemical categories of chromatography, extraction, and volatilization and sublimation methods. This review focuses on chromatography-based systems.     

Yttrium Acetate-Derived Particle Coatings for Mitigating Oxidation and Corrosion of Inconel 625

Sol paint that yields yttrium-based compounds was prepared by mixing four chemical ingredients, yttrium acetate tetrahydrate precursor, diethanolamine, isopropyl alcohol, and hydrochloric acid, and then applied as oxidation/corrosion resistant coatings for Inconel 625 substrates. Annealing the coatings at 500°C developed a coalescent microstructure of coarse particles consisting of amorphous yttrium carbonate as the major component and crystalline yttrium oxide (Y2O3) as the minor one. At 700°C, the yttrium carbonate was transformed into Y2O3 by decarbonation. Increasing the annealing temperature to 900°C led to the formation of the YCrO3 phase yielded by interaction between Y2O3 and the Cr2O3 which had arisen from the oxidation of the underlying Inconel; the YCrO3 phase created a particle coating with a densified microstructure. There were two key factors in mitigating the degree of oxidation of Inconel at 900°C in air: (1) an uptake of oxygen by Y2O3 in the coatings, and (2) a densified coating layer that suppresses the diffusion and permeation of oxygen through it. Furthermore, inhibiting the rate of NaCl-caused corrosion was not only due to the excellent coverage of particle coatings over the entire surfaces of the substrates, but also may be associated with a good adherence of the coatings to the substrates.     

Solid-state linear polarized IR-spectroscopy of croconic and rhodizonic acids

The applications of linear-polarized IR-spectroscopy to oriented colloid suspensions in a nematic host are demonstrated with croconic and rhodizonic acids. The experimental IR vibrational assignments of the solid-state of both neutral compounds are presented. Assignments are supported by theoretical quantum chemical calculations and vibrational analysis at the DFT level of theoretical approximation with the 6-311++G^** basis set.