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  • Author or Editor: R. Dixit x
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Abstract  

A new chelating copolymer (HQDMA) has been synthesized through copolymerization of 8-hydroxyquinoline and dimethylolacetone monomers in the presence of base as a catalyst. This newly developed copolymer ligand (H2L) has been used to prepare a series of five polymeric chelates (ML) by using Zn(II), Cu(II), Ni(II), Co(II) and Mn(II) metal ions. Both the parent ligand and its metal chelates have been systemically investigated in detail to elucidate the chemical structure and thermal behaviour by elemental analyses, spectral (IR and electronic) characterization, number-average molecular mass
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determination and thermogravimetric analysis (TG). In addition to these, magnetic susceptibility measurements have also been carried out for studying geometry and metal-ligand stoichiometry of polymeric chelates. The chemical structure of polychelates on the basis of elemental and IR characterization suggests that the bidentate ligand (H2L) coordinates to metal ions through oxygen atom of the phenolic hydroxyl group by replacing hydrogen atom and nitrogen of the quinoline ring. The studies of magnetic moments and electronic spectra reveal that all polychelates with octahedral geometry are paramagnetic in nature except that of Zn(II) chelate, which is diamagnetic. The thermogravimetric analysis of parent ligand and its metal chelates have shown remarkable difference in mode of thermal decomposition and their thermal stabilities. The kinetic parameter, energy of activation (E a) of thermal decomposition has also been estimated by Broido method.
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Summary

Certain practical aspects in the separation of large biomolecules have been discussed with the chosen examples of storage proteins from two important crops, viz, soybean and peanut. Importance of seeds and storage proteins along with classification and nomenclature of plant proteins is briefly mentioned. The present paper describes an updated knowledge and status on structural features of glycinin (major storage protein of soybean) and arachin (major storage protein of peanut) with respect to their molecular species, subunit structure, and their association-dissociation behavior by using techniques of high-performance liquid chromatography (HPLC), electrophoresis and size exclusion chromatography (SEC) which supplemented each other.

Open access

A reversed phase high-performance liquid chromatographic method has been established for enantioseparation of (R, S)-mexiletine. Two volatile and thermally stable acyl chlorides, viz., (S)-(—)-(N)-trifluoro acetyl prolyl chloride and (1S)-(—)-camphanic chloride, were used as chiral derivatizing reagents. Binary composition of aqueous trifluoroacetic acid (0.1%)-acetonitrile as mobile phase was successful with ultraviolet (UV) detection at 210 nm. The method was optimized and validated for accuracy, precision, and limit of detection. The limit of detection was found to be 45 ng mL−1 and 80 ng mL−1 for the two types of diastereomers. Besides, kinetic resolution was achieved, and the experimental conditions optimized for this purpose provided diastereomeric excess up to 74% for (R)-isomer. On achieving a resolution value greater than 2, the optimized method for analytical enantioseparation was scaled-up to smallscale preparative level, and the native (R)-mexiletine was recovered by acid hydrolysis of the diastereomer.

Open access

Chromium(III) complexes of the type Cr(A)(A′)2, Cr(A)2(A′) and Cr(A)3 have been prepared (whereA is either piperidyldithiocarbamate or morpholyldithiocarbamate andA′ is glycine or oxine or acetylacetone moiety). The mixed ligand complexes have been charac terized by elemental analyses, magnetic susceptibility measurements and thermal studies. The complexes show magnetic moment in the range of 3.5–4.3 B.M. which corresponds to three unpaired electrons. TG studies have also been carried out, in order to study the mode of decomposition of the complexes and to evaluate various kinetic parameters.

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Abstract

Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li2O–71.7SiO2–7.1Al2O3–4.9K2O–3.2B2O3–1.25P2O5–1.25TiO2 were prepared by the melt quench technique. Crystallization kinetics was investigated by the method of Kissinger and Augis–Bennett using differential thermal analysis (DTA). Based on the DTA data, glass ceramics were prepared by single-, two-, and three-step heat treatment schedules. The interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC) and microhardness (MH) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and microhardness (MH) measurements. Crystallization kinetics revealed that Li2SiO3 is the kinetically favored phase with activation energy of 91.10 kJ/mol. An Avrami exponent of n = 3.33 indicated the dominance of bulk crystallization. Based upon the formation of phases, it was observed that the two-stage heat treatment results in highest TEC glass ceramics. The single-step heat treatment yielded glass ceramics with the highest MH.

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