Quantitative FTIR detection in size-exclusion chromatography

With the increasing popularity of evaporative interfaces, detection using Fourier Transform Infrared (FTIR) spectrometry in the mid-infrared region is becoming more important in size-exclusion chromatography (SEC). FTIR spectrometry is a powerful, and potentially very widely applicable, method for obtaining chemical functional group information for each molecular size fraction. Quantitative evaluation of polymer composition across the SEC chromatogram can provide more accurate characterization of heterogeneous polymer samples for problem solving and for material specification. The evaporative interface removes the SEC mobile phase at the exit of the column and deposits the eluting polymer as a continuous film stripe or as a series of discrete films on infrared transparent substrates. Initially this detection approach was used only for qualitative analysis. More recently, it is being used quantitatively. Previously we demonstrated that the quality of the film generated by the evaporative interface was critical to determining the suitability of the resulting FTIR spectra for quantitative analysis. In a continuation of this work, the objective of this paper is to develop a procedure for obtaining valid quantitative results for polymer blends with the interface. Experimental topics include improving the quality of polymer films by post-SEC treatments, off-line FTIR calibrating using other means to obtain high quality polymer films, and utilizing in-line SEC detectors in calibration. Interpretation aspects focus upon peak fitting of FTIR spectra, linear regression, partial least squares, and data pre-processing. PLS prediction with internal calibration using the second derivative of solvent-annealed film spectra was found to provide the best compromise between processing time, accuracy and precision.     

An efficient synthesis of new khellactone-type compounds using potassium hydroxide as catalyst via one-pot,three-component reaction

In the present work, three-component synthesis for novel khellactone-type compounds via the reaction of Meldrum’s acid, aryl aldehydes and 5,7-dihydroxy benzopyrone derivatives was described. In this reaction 10-aryl substituted-9,10-dihydropyrano[2,3-h]benzopyrone-8-ones as new khellactone analogous in the presence of catalytic amount of potassium hydroxide as cheap and green basic catalyst were obtained in good to excellent yields under refluxing methanol.     

An efficient Stille cross‐coupling reaction catalyzed by ortho‐palladated complex of tribenzylamine under microwave irradiation

The catalytic activity of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(μ‐Br)]₂ complex as an efficient, stable and catalyst that is non‐sensitive to air and moisture was investigated in the Stille cross‐coupling reaction of various aryl halides with phenyltributyltins under microwave irradiation. The substituted biaryls were produced in excellent yield in short reaction times using a catalytic amount of this complex in DMF at 100 C. The combination of dimeric complex as homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields in shorter reaction times. Copyright © 2011 John Wiley & Sons, Ltd.     

A new and green approach for regiospecific synthesis of novel chromeno-triazolopyrimidin using tungstic acid immobilized MCM-41 as a reusable catalyst

A novel, eco-friendly and fast route has been developed for the synthesis of new and known triazolo[1,5-a]pyrimidin fused chromone derivatives via a one pot three-component reaction of 3-amino-1,2,4-triazoles, aromatic aldehydes and 4-hydroxycoumarin in aqueous medium at room temperature. These reactions are catalyzed by MCM-41-HWO₄ as a safe and recyclable mesoporous solid acid. It combines successfully the synergistic effect of green chemistry with nanocatalysis. The yields are high and the products were characterized by ¹H NMR, ¹³CNMR spectra and elemental analysis.     

A new analytical definition of the dead material zone for forward extrusion of shaped sections

This article aims to provide a new formulation for the analysis of the extrusion process for non-axisymmetric sections. The upper bound theorem has been used to obtain a generalized kinematically admissible velocity field. The geometry of the deforming region has been formulated considering variation of the dead zone size at different angular positions and three-dimensional curved surfaces have been employed to define the entry and exit surfaces of the deformation zone. Using this analytical method, extrusion of square, rectangular and L-shaped sections were analyzed and the effect of shape complexity on material flow and dead material zone (DMZ) formation under different conditions has been investigated. Physical modelling experiments and finite element analysis were carried out to reveal the capability of the proposed theoretical method.     

Synthesis and morphological investigation of pulsed current formed nano-structured lead dioxide

An electro-forming method was used for the preparation of nano-structured lead dioxide on lead substrate in 4.8 M H₂SO₄. A two electrode system composed of two similarly prepared lead electrodes was employed. A constant current was applied between two electrodes for a short time, followed by a relaxation period. A dark oxidation film of suitable stability and homogeneity was formed on the anode electrode. Different parameters including pulse height, pulse time (t_on) and relaxation time (t_off) were optimized. A change in morphology of lead dioxide from globular to nanofibriliar was observed when the pulse time and relaxation time varied from 0.01 to 10 and 0.1 to 5 s, respectively, at a pulse height of 25 mA cm⁻². A variation in pulse height caused a variation in diameter and length of nanofibers formed at a pulsed time of 0.1 s and relaxation time of 5 s. The scanning electron microscopy (SEM) showed that lead dioxide particles obtained under these conditions have nanofibriliar morphology with an average diameter in the range between 20 and 50 nm and length of 500–1000 nm.     

Unsteady flow and heat transfer analysis of an impinging synthetic jet

The present paper focuses on the analysis of unsteady flow and heat transfer regarding an axisymmetric impinging synthetic jet on a constant heat flux disc. Synthetic jet is a zero net mass flux jet that provides an unsteady flow without any external source of fluid. Present results are validated against the available experimental data showing that the SST/k − ω turbulence model is more accurate and reliable than the standard and low-Re k − ε models for predicting heat transfer from an impinging synthetic jet. It is found that the time-averaged Nusselt number enhances as the nozzle-to-plate distance is increased. As the oscillation frequency in the range of 16–400 Hz is increased, the heat transfer is enhanced. It is shown that the instantaneous Nu distribution along the wall is influenced mainly by the interaction of produced vortex ring and wall boundary layer. Also, the fluctuation level of Nu decreases as the frequency is raised.     

Central composite design with the help of multivariate curve resolution in loadability optimization of RP‐HPLC to scale‐up a binary mixture

Chromatographic method development for preparative targets is a time‐consuming and subjective process. This can be particularly problematic because of the use of valuable samples for isolation and the large consumption of solvents in preparative scale. These processes could be improved by using statistical computations to save time, solvent and experimental efforts. Thus, contributed by ESI‐MS, after applying DryLab software to gain an overview of the most effective parameters in separation of synthesized celecoxib and its co‐eluted compounds, design of experiment software that relies on multivariate modeling as a chemometric approach was used to predict the optimized touching‐band overloading conditions by objective functions according to the relationship between selectivity and stationary phase properties. The loadability of the method was investigated on the analytical and semi‐preparative scales, and the performance of this chemometric approach was approved by peak shapes beside recovery and purity of products.     

One‐pot Synthesis of Benzamidonaphtho[2,1‐b]furans and Benzamidobenzo[b]furans as Novel Polycyclic Heteroaromatic Compounds

An operationally simple, green and efficient procedure for one‐pot synthesis of novel polycyclic heteroaromatic compounds such as benzamidonaphtho[2,1‐b]furans and benzamidobenzo[b]furans has been developed from the reaction of arylglyoxals, benzamide, and phenols. The reactions were mediated with low amounts of yttrium nitrate hexahydrate as a suitable Lewis acid catalyst without using solvent.