A group contribution method for estimation of glass-transition temperature of 1,3-dialkylimidazolium ionic liquids

Glass-transition temperature (T _g) of ionic liquids (ILs) plays a key role in assessment of their potential for electrolyte application purposes. In this communication, a new group contribution model is presented for the prediction of the T _g of 1,3-dialkylimidazolium, a class of ILs, which has great potentialities to serve as electrolyte. To develop this model, the contribution of ILs’ anions and cations is separately considered. This simple model shows a low average relative deviation of 1.94 % for a data set including 109 experimental glass-transition temperature.     

Synthesis of New (Pyrimido[4,5-e][1,3,4] thiadiazin-7-yl)hydrazine Derivatives

New (pyrimido[4,5-e][1,3,4]thiadiazin-7-yl)hydrazines were synthesized via the cyclocondensation of alkyl-2-phenylhydrazinecarbodithioates as bidentate nucleophiles with 5-bromo-2,4-dichloro-6-methylpyrimidine as an electrophile and further replacement of chlorine atom on the seven number position of pyrimido[4,5-e][1,3,4]thiadiazin by hydrazine in boiling ethanol.     

Molecular Basis of the Chemiluminescence Mechanism of Luminol

Light emission from luminol is probably one of the most popular chemiluminescence reactions due to its use in forensic science, and has recently displayed promising applications for the treatment of cancer in deep tissues. The mechanism is, however, very complex and distinct possibilities have been proposed. By efficiently combining DFT and CASPT2 methodologies, the chemiluminescence mechanism has been studied in three steps: 1) luminol oxygenation to generate the chemiluminophore, 2) a chemiexcitation step, and 3) generation of the light emitter. The findings demonstrate that the luminol double-deprotonated dianion activates molecular oxygen, diazaquinone is not formed, and the chemiluminophore is formed through the concerted addition of oxygen and concerted elimination of nitrogen. The peroxide bond, in comparison to other isoelectronic chemical functionalities (−NH−NH−, −N⁻−N⁻−, and −S−S−), is found to have the best chemiexcitation efficiency, which allows the oxygenation requirement to be rationalized and establishes general design principles for the chemiluminescence efficiency. Electron transfer from the aniline ring to the OO bond promotes the excitation process to create an excited state that is not the chemiluminescent species. To produce the light emitter, proton transfer between the amino and carbonyl groups must occur; this requires highly localized vibrational energy during chemiexcitation.     

Investigation of kinetic and mechanism of triphenylphosphine addition to para‐naphthoquinone

This work reports the results of a kinetic and mechanistic investigations of the addition reaction of triphenylphosphine to para‐naphtoquinone in 1,2‐dichloromethane as solvent. The order of reaction with respect to the reactants was determined using initial rate method, and the rate constant was obtained on the basis of pseudo‐first‐order method. Variable time method using Uv–Vis spectrophotometry (at 400 nm) was utilized for monitoring this addition reaction, for which the following Arrhenius equation was obtained: The resulting activation parameters E_a, ΔH^#, ΔG^#, and ΔS^# at 300 K were 13.63, 14.42, 18.75 kcal mol^?1, and ?14.54 cal mol^?1K^?1, respectively. The results suggest that the reaction is first order with respect to both triphenylphosphine and para‐naphthoquinone. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 427–433, 2005     

Quantitation of antioxidants in water samples using ionic liquid dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-ultraviolet detection

A simple and efficient method, ionic liquid-based dispersive liquid-liquid microextraction combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV), has been applied for the extraction and determination of some antioxidants (Irganox 1010, Irganox 1076 and Irgafos 168) in water samples. The microextraction efficiency factors were investigated and optimized: 1-hexyl-3-methylimidazolium hexafluorophosphate [C(6)MIM][PF(6)] (0.06 g) as extracting solvent, methanol (0.5 mL) as disperser solvent without salt addition. Under the selected conditions, enrichment factors up to 48-fold, limits of detection (LODs) of 5.0-10.0 ng/mL and dynamic linear ranges of 25-1500 ng/mL were obtained. A reasonable repeatability (RSD≤11.8%, n=5) with satisfactory linearity (r(2)≥0.9954) of the results illustrated a good performance of the presented method. The accuracy of the method was tested by the relative recovery experiments on spiked samples, with results ranging from 85 to 118%. Finally, the method was successfully applied for determination of the analytes in several real water samples.     

Quantitation of atorvastatin in human plasma using directly suspended acceptor droplet in liquid-liquid-liquid microextraction and high-performance liquid chromatography-ultraviolet detection

A simple and sensitive methodology based on liquid-liquid-liquid microextraction (LLLME) followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) has been successfully developed for the determination of atorvastatin (AT) in human plasma. AT was first extracted from 4.5 mL acidic aqueous sample (diluted plasma, donor phase, pH 1) at temperature 45 °C through 400 μL 1-octanol for 4.5 min, while being agitated by a stirring bar at 1250 rpm. Then, a 5.5 μL free suspended basic aqueous droplet (acceptor phase, pH 10) was delivered to the top-center position of the organic membrane. The mixture was stirred at 650 rpm for 7.5 min and the analyte was back-extracted into the droplet. Finally, the acceptor phase was taken into a microsyringe and injected directly into the HPLC. An enrichment factor of 187 along with substantial sample clean up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 1-500 ng mL⁻¹ with regression coefficient corresponding to 0.996. Limits of detection (S/N = 3) and quantification (S/N = 10) were 0.4 and 1 ng mL⁻¹, respectively. A reasonable relative recovery (91%) and satisfactory intra-assay (4.4-7.0%, n = 6) and inter-assay (4.9-7.7%, n = 8) precision illustrated good performance of the analytical procedure. This technique was eventually applied for the determination of AT in human plasma after oral administration of 40 mg single dose of drug. The protocol proved to be highly cost-effective and reliable for the screening purpose.     

Synthesis,spectroscopic investigations,and computational study of 4-((9,10-dioxo-9,10-dihydroanthracen-1-yl)oxy)-3-methoxybenzaldehyde

4-((9,10-dioxo-9,10-dihydroanthracen-1-yl)oxy)-3-methoxybenzaldehyde has been synthesized in an attempt to obtain a new photochromic compound. The optimized molecular structure, mole fractions of title compound in trans and ana forms have been investigated. UV-visible spectra of the compound were also recorded. Upon irradiation with 300 nm light, the camel solid turned orange, in which a visible absorption band was observed at 475 nm. The electronic properties, such as HOMO, LUMO and band gap energies were obtained by the time-dependent DFT (TD-DFT) approach. The predicted nonlinear optical properties of the title compound are much greater than those of urea. Transition structures were calculated by QST3 and IRC methods which yielded the potential energy surface and activation energy.     

Flow pattern analysis of linear gradient flow distribution

This paper uses the Oseen transformation to solve the differential equations governing motion of the vertical linear gradient flow distribution close to a wall surface. The Navier-Stokes equations are used to consider the inertia term along the flow direction. A novel contour integral method is used to solve the complex Airy function. The boundary conditions of linear gradient flow distribution for finite problems are determined. The vorticity function, the pressure function, and the turbulent velocity profiles are provided, and the stability of particle trajectories is studied. An L_x-function form of the third derivative circulation is used to to simplify the solution. Theoretical results are compared with the experimental measurements with satisfactory agreement.     

Graphene oxide/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@polythionine nanocomposite as an efficient sorbent for magnetic solid-phase extraction followed by high-performance liquid chromatography for the determination of duloxetine in human plasma

Herein, an efficient graphene oxide/Fe₃O₄@polythionine (GO/Fe₃O₄/PTh) nanocomposite sorbent was introduced for magnetic solid-phase extraction combined with high-performance liquid chromatography–ultraviolet detection of duloxetine (DLX) in human plasma. To prepare the sorbent, an oxidative polymerization of thionine on the surface of magnetic GO was utilized while PTh was simply used as a surface modifier to improve extraction efficiency. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, vibrating sample magnetometry, Fourier transform-infrared spectroscopy and Brunauer–Emmett–Teller technique were applied to characterize the prepared nanoparticles. Firstly, effective parameters controlling the performance of the extraction process were evaluated in detail and optimized. Under the optimized conditions, calibration curve showed linearity in the range of 2–2500 ng mL^?1 with regression coefficient corresponding to 0.998. Limits of detection (LOD, S/N = 3) and quantification (LOQ, S/N = 10) were 0.5 and 2 ng mL^?1, respectively. Reasonable intra-assay (3.5–4.5%, n = 6) and inter-assay (3.8–6.7%, n = 9) precision represented acceptable performance of the procedure. The applicability of the method was successfully extended to the determination of DLX in human plasma after oral administration of 60 mg single dose of the drug and finally some pharmacokinetic data was achieved.     

Thermodynamic Studies of Insulin Loading into a Glucose Responsive Hydrogel Based on Chitosan‐polyacrylamide‐polyethylene Glycol

The insulin therapy constitutes the preferred treatment for Diabetes Mellitus (DM). The traditional insulin therapy, which consists of daily subcutaneous insulin injections to control blood glucose level, is not able to regulate the blood glucose level precisely. In this research, to facilitate the diabetic patient life, an intelligent drug delivery system based on a biodegrable biopolymer to control the insulin release, was designed. In this system, chitosan‐polyethylene glycol hydrogel and glucose oxidize play the role of drug carrier and glucose biosensor, respectively. To increase the hydrogel drug loading capacity, hydrogels with different PEG content were synthesized and insulin was loaded by swelling‐diffusion method into them. The loaded hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), High performance liquid chromatography (HPLC), and Thermogravimetric analysis (TGA). Finally, the thermodynamic study for insulin loading process was performed to investigate the stability of the drug in the system.