Effects of thermal treatment of biaxially oriented poly(ethylene terephthalate)

Two distinguishable effects of thermal exposure of biaxially oriented poly(ethylene terephthalate) (PET) have been observed in the temperature range from room temperature to 140°C. Upon heating above the glass transition temperature T_g of the film an irreversible shrinkage of a few percent occurred with a concomitant decrease in the rate of creep. Some loss of orientation in the noncrystalline phase with an attendant slight increase in density is believed to be responsible. Since the film was anisotropic in its plane, different amounts and rates of shrinkage were observed along with differing thermal expansion coefficients in various directions relative to the primary optic axis. Upon cooling the 50% crystalline PET from above T_g to lower temperatures, reversible “physical aging” was observed. Creep rates were found to decrease with the residence time below T_g. As with purely amorphous polymers, the effects of the aging are removed by heating the specimen above T_g where the density of the amorphous phase achieves equilibrium values.     

Liquid Chromatographic Resolution of the Enantiomers of Metoprolol and Carvedilol in Pharmaceutical Formulations by use of Marfey’s Reagent and its Variants

JPC – Journal of Planar Chromatography – Modern TLC - A simple and rapid method has been established for indirect separation of the enantiomers of (R,S)-metoprolol and (R,S)-carvedilol...     

High-performance liquid chromatographic enantioseparation of (R,S)-fluoxetine using Marfey's reagent and (S)-N-(4-nitrophenoxycarbonyl) phenylalanine methoxyethyl ester as chiral derivatizing reagents along with direct thin-layer chromatographic resolution and isolation of enantiomers using L-tartaric acid as mobile phase additive

Chiral assay of enantiomers of fluoxetine was achieved in pharmaceutical formulations using direct and indirect methods. L-tartaric acid was used as a mobile phase additive in thin-layer chromatography; the enantiomers were separated and isolated and were used to determine the elution order in HPLC. (R,S)-flouxetine was derivatized with (S)-N-(4-nitrophenoxycarbonyl)phenylalanine methoxyethyl ester [(S)-NIFE], Marfey's reagent and 1-fluoro-2,4-dinitrophenyl-L-methionine amide (FDNP-L-Met-NH?. The diastereomers were separated using RP-HPLC. The effect of flow rate and TFA concentration on resolution was studied. The diastereomers obtained by derivatization with FDNP-L-Met-NH? were also separated by RP-TLC.     

Sr induced modification of structural,optical and magnetic properties in Bi1−xSrxFeO3 (x = 0, 0.01, 0.03, 0.05 and 0.07) multiferroic nanoparticles

Multiferroic nanoparticles of Bi_1?xSr_xFeO₃ (x = 0, 0.01, 0.03, 0.05 and 0.07) were prepared by a facile sol–gel route and the variation of their structural, optical, dielectric and magnetic properties on strontium concentration has been studied. XRD and TEM results confirm the phase purity of the samples having high degree of crystallinity and monodispersity. The average particle size shows an exponential decline with increase in Sr concentration. A shape transformation from a multifaceted polygon to a spherical one has been observed as Sr concentration in the sample increases to 5%. In the second derivative FTIR spectra, the intensity of vibration peak at ～593 cm^?1 that is characteristic of rhombohedral BiFeO₃ is seen to decrease after Sr doping. All the samples showed typical M–H behavior of a ferromagnet with saturation magnetization achieved within an applied magnetic field of 10 kOe. The sample with 3% Sr substitution displayed saturation and remanent magnetization values 1.37 emu/g and 0.32 emu/g respectively that are highest among all the samples studied. Presence of exchange coupling produced due to interaction between the antiferromagnetic core and ferromagnetic shell is also observed in all Bi_1?xSr_xFeO₃ nanoparticles.     

Different approaches of impregnation for resolution of enantiomers of atenolol,propranolol and salbutamol using Cu(II)-l-amino acid complexes for ligand exchange on commercial thin layer chromatographic plates

Atenolol and propranolol (the β-blocking agents) and salbutamol (broncho- and vasodilator) were resolved into their enantiomers by adopting different modes of loading/impregnating the Cu(II) complexes of l-proline (l-Pro), l-phenylalanine (l-Phe), l-histidine (l-His), N,N-dimethyl-l-phenylalanine (N,N-Me₂-l-Phe), and l-tryptophan (l-Trp) on commercial precoated normal phase plates. The three different approaches were (A) using the Cu(II)-l-amino acid complex as chiral mobile phase additive, (B) ascending development of plain commercial plates in the solutions of Cu complex, and (C) using a solution of Cu(II) acetate as mobile phase additive for the commercial TLC plates impregnated with ascending development of plates in the solutions of amino acid. Spots were located using iodine vapour. The results obtained for the three methods have been compared for their efficiency and the issue of involvement of the Cu(II) cation for the best performance of the three methods has been discussed with respect to the same mobile phase. The detection limit is 0.18 μg for each enantiomer.     

Indirect enantioresolution of (R,S)‐mexiletine by reversed‐phase high‐performance liquid chromatography via diastereomerization with [(S,S)‐O,O'‐di‐p‐toluoyl tartaric acid anhydride], (S)‐naproxen and nine chiral reagents synthesized as variants of Marfey's reagent

Eleven chiral derivatizing reagents (CDRs) were used for preparation of diastereomers of (R,S)‐mexiletine containing a primary amino group in close proximity to the stereogenic center. One anhydride, namely [(S,S)‐O,O'‐di‐p‐toluoyl tartaric acid anhydride] was synthesized and (S)‐naproxen was used as such as the chiral derivatizing reagent. The other nine CDRs were synthesized by substituting one of the fluorine atoms in 1,5‐difluoro‐2,4‐dinitrobenzene with six amino acid amides and three amino acids. The diastereomers were separated by reversed‐phase high‐performance liquid chromatography. The method was validated for linearity, accuracy, limit of detection and limit of quantification. The limit of detection was found in the range of 10–30 pmol. Copyright © 2010 John Wiley & Sons, Ltd.     

Separation of Aminoglycosides by Normal- and Reversed-Phase TLC

JPC – Journal of Planar Chromatography – Modern TLC - The normal-phase (NP) and reversed-phase (RP) thin-layer chromatographic separations of aminoglycosides (streptomycin, kanamycin,...     

Synthesis,Characterization, and Antibacterial Activity of Novel (1H‐Benzo[d]imidazole‐2‐yl)‐6‐(diethylamino)‐3H‐one‐xanthene,Phenoxazine, and Oxazine

A series of novel (1H‐benzo[d]imidazole‐2‐yl)‐6‐(diethylamino)‐3H‐one‐xanthene, phenoxazine, and oxazine derivatives have been synthesized from 2‐(2′,4′‐dihydroxyphenyl) benzimidazole intermediate. Synthesized compounds 8a , 8b , 8c , 8d are fluorescent in solution, photophysical properties of compounds were studied and results revealed that compounds absorb and emit in UV–visible region with good fluorescence quantum yield. Synthesized compounds are thermally stable up to 300°C. The antibacterial activities of the synthesized compounds were studied by the well‐diffusion method. Escherichia coli (ATTC‐25922), Staphylococcus aureus (ATCC‐25923), Micrococcus (ATCC‐4698), and Bacillus subtilis (ATCC‐55422) were used to investigate the antibacterial activities.