HPLC and GC Methods for Determination of Lubricants and Their Evaluation in Analysis of Real Samples of Polyethylene

High performance liquid chromatography (HPLC) and gas chromatography (GC) are introduced for analysis of polymer lubricants (stearamide, oleamide and erucamide). In the HPLC method, a reverse phase octadecylsilane (ODS) column along with acetonitrile/methanol (60:40) as a mobile phase were used. Detection of analytes was performed by a UV detector at 202 nm. The analysis time was less than 8 min. In the GC method, polar capillary column and flame ionization detector (FID) were used for separations and detection, respectively. The analysis time by GC was longer than HPLC and was about 30 min. Limits of detection, linear range and repeatability of both methods are similar, but determination of oleamide in real samples by HPLC method is difficult due to complexity of the initial part of HPLC chromatogram in polyethylene samples. That problem is not observed in the GC method. Detection limits in both methods for all analytes are lower than 0.003% which are much lower than the amount of lubricants in commercial polymers (0.05–0.2%).     

Ab initio study of aerogen-bonds between some heterocyclic compounds of benzene with the noble gas elements (Ne,Ar, and Kr)

Structural Chemistry - Ab initio calculations have been performed to study the complexes between the noble gas elements (Ae = Ne, Ar, Kr) with a series of benzene isoelectronic heterocyclic...     

Introduction of a new dichlorophen electrochemical sensor relying on the modified glassy carbon electrode (GCE) with carboxyl-functionalized graphene oxide/poly (L-arginine)

Journal of Solid State Electrochemistry - Dichlorophen (Dcp), a harmful environmental pollutant, is broadly utilized in veterinary medications, chemical fertilizers, pesticides, cosmetics, and...     

Hydrangenone, a new isoprenoid with an unprecedented skeleton from Salvia hydrangea

Hydrangenone, a new heptacyclic isoprenoid with a 6/7/6/5/5 membered carbon ring skeleton, was isolated from the aerial parts of Salvia hydrangea. The structure was established by extensive NMR spectroscopic methods. The relative and absolute configuration of 1 was assigned by NOESY and X-ray crystallographic analysis and by comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compound 1 showed in vitro antiplasmodial activity, with an IC(50) value of 1.4 μM against P. falciparum. A plausible biosynthetic pathway of 1 was also proposed.     

A novel numerical scheme for the investigation of surface tension effects on growth and collapse stages of cavitation bubbles

In the present study the effects of surface tension on the growth and collapse stages of cavitation bubbles are studied individually for both spherical and nonspherical bubbles. The Gilmore equation is used to simulate the spherical bubble dynamics by considering mass diffusion and heat transfer. For the collapse stage near a rigid boundary, the Navier–Stokes and energy equations are used to simulate the flow domain, and the VOF method is adopted to track the interface between the gas and the liquid phases. Simulations are divided into two cases. In the first case, the collapse stage alone is considered in both spherical and nonspherical situations with different conditions of bubble radius and surface tension. According to the results, surface tension has no significant effects on the flow pattern and collapse rate. In the second case, both the growth and collapse stages of bubbles with different initial radii and surface tensions are considered. In this case surface tension affects the growth stage considerably and, as a result, the jet velocity and collapse time decrease with increasing surface tension coefficient. This effect is more significant for bubbles with smaller radii.     

Momentum transport from current-driven reconnection in the reversed field pinch

We calculate momentum transport from tearing fluctuations in a reversed field pinch with sheared flow, considering both the effect of a single tearing mode (through quasilinear theory and MHD computation) and multiple tearing modes (through nonlinear MHD computation). A single tearing mode transports momentum, via Maxwell and Reynolds stresses, more rapidly than classical viscous forces. Moreover, the transport is enhanced by nonlinear coupling of multiple modes.     

The X<Superscript>−</Superscript>···benzohydrazide complexes: the interplay between anion-π and H-bond interactions

The compounds containing the benzohydrazide (BH) nucleus have a variety of biological activities because of various noncovalent intermolecular interactions. The interplay between anion-π and H-bond interactions, which can affect the activity of compounds, has been investigated in ten substituted BH exposed to the chloride ion using the quantum mechanical calculations. The total interaction energy is separated into the anion-π (ΔE _Aπ) and H-bond (ΔE _HB) contributions where both interactions are presented in the complexes. The electron-withdrawing substituents (EWSs) increase |ΔE _Aπ| and decrease |ΔE _HB|, while reversed changes are observed with the electron-donating substituents (EDSs). In addition, the total binding energy (ΔE) becomes more/less negative in the presence of EWSs/EDSs. The synergetic effects of mentioned interactions and substituent effects have also been investigated using the atoms in molecules (AIM), natural bond orbital (NBO) and molecular electrostatic potential (MEP) analyses. A good correlation is found between the energy data and the Hammett constants, the minimum of electrostatic potential (V _min) and the results of population analyses.     

The molecular Hamiltonian in internal coordinates

A systematic approach for the derivation of the exact translational–rovibronic (non-relativistic) Hamiltonian for a polyatomic molecule consisting of N nuclei and n electrons is presented. All coupling terms which contribute to the total energy are identified. The Hamiltonian is greatly simplified by taking the internal coordinates (bond lengths and bond angles) as the vibrational variables. The translational–rovibronic Hamiltonian of triatomic molecules are considered as an application for this general formulation.