A method of calculating the second dimension retention index in comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

A method was developed to calculate the second dimension retention index of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC/TOF-MS) data using n-alkanes as reference compounds. The retention times of the C(7)-C(31) alkanes acquired during 24 isothermal experiments cover the 0-6s retention time area in the second dimension retention time space, which makes it possible to calculate the retention indices of target compounds from the corresponding retention time values without the extension of the retention space of the reference compounds. An empirical function was proposed to show the relationship among the second dimension retention time, the temperature of the second dimension column, and the carbon number of the n-alkanes. The proposed function is able to extend the second dimension retention time beyond the reference n-alkanes by increasing the carbon number. The extension of carbon numbers in reference n-alkanes up to two more carbon atoms introduces <10 retention index units (iu) of deviation. The effectiveness of using the proposed method was demonstrated by analyzing a mixture of compound standards in temperature programmed experiments using 6 different initial column temperatures. The standard deviation of the calculated retention index values of the compound standards fluctuated from 1 to 12 iu with a mean standard deviation of 5 iu.     

Thermal analysis of corrosion products formed on carbon steel in ammonium chloride solution

The influence of different ions NO₃ ^? and SO₄ ^2? on the carbon steel corrosion in ammonium chloride was investigated using mass loss measurements and potentiodynamic polarization. Corrosion products were analyzed using X-ray photoelectron spectroscopy (XPS) and simultaneous thermal and differential scanning calorimetry (TG/DSC). XPS analysis shows that the main product of corrosion is a non-stoichiometric Fe³⁺ oxyhydroxide, consisting of a mixture of FeO(OH) and FeO(OH) containing inclusions of these anions, species such as Fe³⁺O(OH,Cl^?); Fe³⁺O(OH,SO₄ ^2?); and Fe³⁺O(OH,NO₃ ^?). TG/DSC confirms the decomposition of the rusty products formed by chemical corrosion, compounds like Fe³⁺ oxyhydroxides, with β-FeOOH as the major phase, crystal structure of which may contain Cl^?, NO₃ ^?, and SO₄ ^2?—e.g., akaganeite [Fe³⁺O(OH,A)].     

Expanding the 0D Rb7M3X16 (M=Sb,Bi; X=Br,I) Family: Dual-Band Luminescence in Rb7Sb3Br16

Inorganic, lead-free metal halides are widely sought after following the rise of the halide perovskites as outstanding optoelectronic materials, due to their enhanced stability and reduced toxicity. Herein, we report on the solvothermal synthesis of Rb₇Sb₃Br₁₆, which exhibits a 0D structure comprised of [SbBr₆]³⁻ octahedra and edge-sharing bioctahedra [Sb₂Br₁₀]⁴⁻ dimers that order into layers along the c-axis. This all-inorganic material is air-stable and exhibits weak orange photoluminescence (PL) at room temperature. Low-temperature PL and PL excitation (PLE) measurements reveal the presence of two distinct emission bands that originate from these structural units, with the high-energy emission quenching as temperature rises beyond 150 K. We are also able to obtain Rb₇Bi₃Br₁₆ and Rb₇Bi₃I₁₆ which both crystallize in orthorhombic symmetry, with Rb₇Bi₃Br₁₆ presenting weak low-temperature luminescence while Rb₇Bi₃I₁₆ is non-luminescent. This work expands the library of emissive inorganic metal halides and provides further evidence for the efficacy of low-dimensional Sb−X luminescent centers based on octahedral and edge-sharing [Sb₂X₁₀]⁴⁻ dimers.     

Influencing polymer properties by regiospecific complexation

ABA block-copolymers in which the A segments are capable of forming complexes and B is a non-complexing segment, have been used to prepare polymer materials with properties that can be changed by adding a complexing agent. The complex forming segments were poly(ethylene oxide) (PEO), linear polyethylenimine (LPEI) and poly(N-tert-butylethylenimine) (PTBEI). Commercially available liquid ABA block-copolymers, in which A is PEO and B is poly(propylene oxide), were investigated with high molar mass poly(acrylic acid) (PAA) as the complexing agent for PEO. It was found that the mixtures containing 3 to 7 wt.-% of PAA, showed a marked shear-thickening behavior leading eventually to gelation. This was attributed to the transformation of intramolecular polymer complexes, at low shear rates, to intermolecular complexes, at high shear rates, due to the chain stretching of PAA. ABA copolymers in which A is LPEI or PTBEI and B polytetra-hydrofuran (PTHF), were prepared. Complexation of these copolymers with low molecular weight poly-acids or PAA in polar and non-polar solvents as well as in bulk have been investigated. ABA copolymers in which A is PEO and B a PTHF segment were prepared. These block-copolymers show two melting points: one at appr. 55°C, due to the PEO segments, and one at appr. 30°C due to the PTHF. Upon addition of alkali metal salts such as sodium iodide or sodium thiocyanate, complexes with PEO are formed and as a consequence, the melting point of the PEO segments shifts to appr. 160°C. The complexed materials behave as thermoplastic elastomers up to that temperature.     

Synthesis and characterization of magnetite particles covered with α-trietoxysilil-polydimethylsiloxane

New silicon magnetite ferrofluids were prepared by dispersing siloxane-coated magnetite particles in polydimethylsiloxane with low or high molecular weights. Ferrofluids are stable colloidal dispersions of ultra fine covered magnetite particles, which may be selected for a specific application. We demonstrated new methods of stabilizing the magnetic particles by reacting the hydroxyl groups on the surface of magnetite particles with terminal ethoxy groups of polydimethylsiloxane, followed by their dispersion in silicon fluids. The new silicon ferrofluids were tested from the morphology, magnetic properties/losses, and rheological properties point of view.     

On incomplete polynomials

Approximation of a monomial by incomplete polynomials was the subject of several investigations. Here the setting is inverted (approximating a polynomial by monomials) and generalized (approximating a polynomial by incomplete polynomials).     

The effects of the microscopical theory of the Coriolis forces on nuclear beta-decay155Eu →155Gd

The wave functions yielded by the microscopical non-adiabatic treatment of the Coriolis interaction proposed in Dubna by Pyatov, Chernej and Baznat have been used in order to calculate the beta decay observables of some allowed transitions of the¹⁵⁵Eu nucleus. The Coriolis interaction effects are important especially for the absoluteft values (an important improvement is obtained) and for theβ-γ circular polarization correlation.     

Combining Biginelli multicomponent and click chemistry: generation of 6-(1,2,3-triazol-1-yl)-dihydropyrimidone libraries

Efficient solution-phase protocols for the high-throughput synthesis of 6-(1,2,3-triazol-1-yl)-dihydropyrimidones are reported. The multistep sequence involves the initial bromination of dihydropyrimidones precursors (DHPMs, Biginelli compounds) at the C6-methyl position, using a recyclable polymer-supported brominating agent under rapid flow-through conditions (residence time of 1 min). The 6-bromomethyldihydropyrimidone intermediates were subsequently subjected to a microwave-assisted azidation step (25 min), providing the key 6-azidomethyldihydropyrimidone precursors. In the final step of the sequence, the azides were treated with terminal acetylenes under Cu(I) catalysis (azide-acetylene ligation, "click chemistry") to provide the target 6-(1,2,3-triazol-1-yl)-dihydropyrimidones in a regiospecific fashion (1,4-triazoles) in moderate overall yield utilizing controlled microwave irradiation (20 min). In total, a library of 27 compounds was prepared with 4 points of diversity.     

Ion soft-landing into liquids: Protein identification,separation, and purification with retention of biological activity

Protein ions, after mass spectrometric separation, can be soft-landed into liquid surfaces with preservation of their native structures. Retention of biological activity is strongly favored in glycerol-based surfaces but not in self-assembled monolayer solid surfaces. Soft-landing efficiency for multiply-charged hexokinase ions was found to be some four times higher for a glycerol/fructose liquid surface than for a fluorinated self-assembled monolayer surface. Soft-landing into liquid surfaces is also shown to allow (1) protein purification, (2) on-surface identification of the soft-landed material using MALDI, and (3) protein identification by in-surface tryptic digestion. Pure lysozyme was successfully isolated from different mixtures including an oxidized, partially decomposed batch of the protein and a partial tryptic digest. Liquid glycerol/carbohydrate mixtures could be used directly to record MALDI spectra on the soft-landed compounds provided they were fortified in advance with traditional MALDI matrices such as p-nitroaniline and alpha-cyano-4-hydroxycinnamic acid. Various proteins were soft-landed and detected on-target using these types of liquid surface. Soft-landing of multiply-charged lysozyme ions onto fluorinated self-assembled monolayer surfaces was found to occur with a limited amount of neutralization, and trapped multiply-charged ions could be desorbed from the surface by laser desorption. Initial data is shown for a new approach to protein identification that combines top-down and bottom-up approaches by utilizing protein ion soft-landing from a protein mixture, followed by tryptic digestion of the landed material and detection of characteristic tryptic fragments by MALDI.     

Motion of spheres along a fluid-gas interface

A system of many spherical particles, suspended in a quiescent fluid and touching a planar free fluid-gas interface, is considered. Stick fluid boundary conditions at the sphere surfaces are assumed. The free surface boundary conditions are taken into account with the use of the method of images. For such a quasi-two-dimensional system, the one-sphere resistance operator is calculated numerically. Moreover, the corresponding friction and mobility tensors are constructed from irreducible multipole expansion. Finally, the long-distance terms of the two-sphere mobility tensor are evaluated explicitly up to the order of 1/r3, where r is the interparticle distance. Experiments which have motivated this work are outlined.