Efficient 2,4,6‐trichloro‐1,3,5‐triazine‐catalyzed synthesis of 2‐arylbenzothiazoles and bisbenzothiazoles by condensation of 2‐aminithiophenol with aldehydes under mild conditions

2,4,6‐Trichloro‐1,3,5‐triazine efficiently catalyzed the condensation reactions between 2‐aminothiophenol and aromatic aldehydes to afford 2‐arylbenzothiazolles in good‐to‐excellent yields. Simple and mild reaction conditions, the use of a cheap catalyst and easy work up, and isolation are notable features of this method. J. Heterocyclic Chem., (2011).     

Ionic Liquid Promoted One-Pot Three-Component Reaction: Synthesis of Annulated Imidazo[1,2-a]azines Using Trimethylsilylcyanide

Imidazo[1,2-a]azine derivatives are synthesized by a one-pot three-component reaction of an 2-aminoazine, an aldehyde, and trimethylsilylcyanide in the presence of 1-n-butyl-3-methylimidazolium bromide as a recoverable ionic liquid, in moderate to excellent yields with relatively short reaction times.     

Can commercial peanut assay kits detect peanut allergens?

Peanut is the food group mostly associated with severe and fatal allergic reactions. In the United States, more than 90% of peanut-allergic individuals' serum IgE recognized peanut proteins Ara h 1 and Ara h 2, thus establishing these proteins as major peanut allergens. The amount of Ara h 1 and Ara h 2 in 3 varieties of peanut cultivars that are commonly processed in the industrialized countries was determined to be 12-16 and 6-9%, respectively. Current commercial peanut test kits use polyclonal peanut-specific antibodies to detect soluble or buffer extractable peanut proteins. Because the 2 major peanut allergens Ara h 1 and Ara h 2 are isolated from soluble peanut proteins, it is generally assumed that these commercial kits can detect peanut allergens, although none of these kits claims to detect peanut allergen. This study showed for the first time that the peanut test kits could, in fact, detect major peanut allergens Ara h 1 and Ara h 2 in both native or heat-denatured structures; therefore, these kits qualified to be classified as peanut allergen enzyme-linked immunosorbent assays.     

Liquid chromatography/tandem mass spectrometric bioanalysis using normal-phase columns with aqueous/organic mobile phases - a novel approach of eliminating evaporation and reconstitution steps in 96-well SPE

Bioanalytical methods using automated 96-well solid-phase extraction (SPE) and liquid chromatography with electrospray tandem mass spectrometry (LC/MS/MS) are widely used in the pharmaceutical industry. SPE methods typically require manual steps of drying of the eluates and reconstituting of the analytes with a suitable injection solvent possessing elution strength weaker than the mobile phase. In this study, we demonstrated a novel approach of eliminating these two steps in 96-well SPE by using normal-phase LC/MS/MS methods with low aqueous/high organic mobile phases, which consisted of 70-95% organic solvent, 5-30% water, and small amount of volatile acid or buffer. While the commonly used SPE elution solvents (i.e. acetonitrile and methanol) have stronger elution strength than a mobile phase on reversed-phase chromatography, they are weaker elution solvents than a mobile phase for normal-phase LC/MS/MS and therefore can be injected directly. Analytical methods for a range of polar pharmaceutical compounds, namely, omeprazole, metoprolol, fexofenadine, pseudoephedrine as well as rifampin and its metabolite 25-desacetyl-rifampin, in biological fluids, were developed and optimized based on the foregoing principles. As a result of the time saving, a batch of 96 samples could be processed in one hour. These bioanalytical LC/MS/MS methods were validated according to "Guidance for Industry - Bioanalytical Method Validation" recommended by the Food and Drug Administration (FDA) of the United States.     

CCD camera full range pH sensor array

Changes in colors of an array of optical sensors that responds in full pH range were recorded using a CCD camera. The data of the camera were transferred to the computer through a capture card. Simple software was written to read the specific color of each sensor. In order to associate sensor array responses with pH values, a number of different mathematics and chemometrics methods were investigated and compared. The results show that the use of “Microsoft Excel's Solver” provides results which are in very good agreement with those obtained with chemometric methods such as artificial neural network (ANN) and partial least square (PLS) methods.     

Spectrophotometric determination of vanadium in different oxidation states with pyrogallol

Determination of vanadium at low concentrations is easily performed with pyrogallol as a ligand which forms a bluish-violet complex with vanadium(III), (IV) or (V). The colour of the bluish-violet complex (lambda(max) = 580 nm) contrasts well with the colour of both pyrogallol and vanadium. The complexes are stable for several hours. Beer's law is obeyed over the range 0-14 mug/ml vanadium at pH 6. The apparent molar absorptivity at 580 nm is (7.75 +/- 0.25) x 10(3)1.mole(-1).cm(-1). The effects of diverse ions on the determination of vanadium have been fully studied. Only Mo(VI) and W(VI) interfere seriously. The method is selective, sensitive and can be applied to the determination of total vanadium in a variety of samples.     

New 12-tungstophosphate-based organic-inorganic hybrid. Synthesis, spectroscopic characterization, X-ray determination and thermal behavior

12-Tungstophosphate-based organic/inorganic hybrid, [HNMPA]₃[O₄₀PW₁₂].0.5NMPA.₂H₂O (NMPA = N-methylpropionamide) was synthesized and characterized by IR, UV-Vis, ¹H, ¹³C and ³¹P NMR spectroscopies, elemental analysis, TGA, DTA and single crystal X-ray determination. Full decomposition of the hybrid leads to WO₃ powder was studied by IR, SEM and XRD.     

Effect of shear on intramolecular and intermolecular association during cross-linking of hydroxyethylcellulose in dilute aqueous solutions

Intramolecular and intermolecular associations of dilute aqueous alkali solutions of hydroxyethylcellulose (HEC) in the presence of a chemical cross-linker agent (divinyl sulfone, DVS) are studied with the aid of dynamic light scattering (DLS) and rheological methods. At quiescent state, DLS detected only interchain aggregation of HEC during the cross-linker reaction, and the magnitude and start of this effect depend on the cross-linker concentration. The growth of clusters has been investigated at various stages in the course of the cross-linking process by quenching the reaction mixture to a lower pH. After quenching, no further association of the species occurred. When the dilute reaction mixtures are subjected to shear, intrapolymer cross-linking with contraction of the molecules is observed, and at moderate shear rates this effect is followed by interpolymer cross-linking and the formation of aggregates at longer times. The rate of the growth of the multichain aggregates decreases with increasing shear rate, and at sufficiently high shear rates no cross-linking effect is observed. Depending on the shear rate, the aggregates continue to grow until they reach a certain size where an incipient breakup of interaggregate chains can be observed. The delicate interplay between intramolecular and intermolecular association effects is governed by factors such as the magnitude of the shear rate, polymer concentration, and cross-linker density.     

Nonlinear optics and crystalline whispering gallery mode cavities

We demonstrate parametric frequency doubling in a whispering gallery cavity made of periodically poled lithium niobate. This demonstration is an example of utility of such crystalline optical whispering gallery resonators with very high Q factors, which we have fabricated.