NISCAIR Online Periodicals Repository Collection: IJC-A Vol.51A(11) [November 2012]

Kinetics and mechanism of oxidation of tyrosine by vanadium(V) in aqueous hydrochloric and ethanoic acid medium

Mon, 29 Oct 2012 22:58:59 GMT

Title: Kinetics and mechanism of oxidation of tyrosine by vanadium(V) in aqueous hydrochloric and ethanoic acid medium

Authors: Onkar, A S; Naik, P N; Gunagi, S D; Nandibewoor, S T; Chimatadar, S A

Page(s): 1574-1579

Fluorescence and CD studies of protein denaturation in the presence of sub-picomolar gold nanoparticles

Mon, 29 Oct 2012 22:58:59 GMT

Title: Fluorescence and CD studies of protein denaturation in the presence of sub-picomolar gold nanoparticles

Authors: Ojha, K; Chowdhury, P K; Ganguli, A K

Abstract: The dependence of nanoparticle concentration on the conformation of bovine serum albumin has been studied. A very small but consistent enhancement in the tryptophan emission is observed in the presence of sub-picomolar concentration of gold nanoparticles. At this concentration, the bovine serum albumin unfolding profile in presence and absence of nanoparticles are quite similar and the protein conformation remains essentially conserved.

Page(s): 1561-1566

Primary amine-based palladium(II) complexes as catalysts for Suzuki-Miyaura reaction: Experimental and theoretical investigations on the effects of substituents on nitrogen atom

Mon, 29 Oct 2012 22:58:59 GMT

Title: Primary amine-based palladium(II) complexes as catalysts for Suzuki-Miyaura reaction: Experimental and theoretical investigations on the effects of substituents on nitrogen atom

Authors: Tairai, Archana; Bhattacharyya, Pradip K; Kar, Rahul; Das, Pankaj

Abstract: Catalytic efficiencies of eight primary amine-based palladium(II) complexes of general formula, trans-[PdCl₂(RNH₂)₂] (1L₁-L₈), have been evaluated for the Suzuki-Miyaura reaction of 4-bromonitrobenzene with phenylboronic acid at room temperature in water. The efficiencies of the catalysts follow the order: Ph₃CNH₂ (L₈) > Ph₂CHNH₂ (L₇) > Ph₂CH₂NH₂ (L₆) > ^tBuNH₂ (L₄) > CyNH₂ (L₅) > ⁱPrNH₂ (L₂) > ⁿBuNH₂ (L₃) > ⁿPrNH₂ (L₁). In order to ascertain the parameters affecting catalytic efficiencies, DFT based reactivity descriptors have been analyzed for the ligands. Good linear correlation is obtained between the observed yield (%) and the gas phase reactivity descriptors (chemical hardness, chemical potential and electrophilicity index). Good-to-excellent yields of coupling products are achieved using the 1L₈ complex as the catalyst for a range of aryl halides.

Page(s): 1545-1552

Flow injection preconcentration system using a new functionalized resin for determination of cadmium(II) by flame atomic absorption spectroscopy

Mon, 29 Oct 2012 22:58:59 GMT

Title: Flow injection preconcentration system using a new functionalized resin for determination of cadmium(II) by flame atomic absorption spectroscopy

Authors: Saxena, Reena; Singh, Suneeti

Abstract: A rapid and sensitive method for the determination of trace level of Cd(II) in industrial effluents by flame atomic absorption spectroscopy has been developed. The technique is based on the online flow injection preconcentration of Cd(II) ions on a mini column, packed with Amberlite XAD-2 functionalized with xylenol orange. Flow injection variables have been optimized for the determination and quantitative preconcentration of Cd(II). Cd(II) ions are effectively retained on the mini column at pH 5.0. A high sorption capacity of 348 µmol/g of dry resin is obtained and chelating resin can be reused for 70-80 cycles of sorption desorption without any significant change in the sorption capacity. With preconcentration times of 60 s and 120 s at a sample loading flow rate of 5 mL min^-1, preconcentration factors of 17 and 32 are obtained. The calibration graph using the preconcentration system for Cd(II) is linear over the concentration range of 0-120 µg L^-1. The precision for 5 replicate measurements are 1.68 and 1.12 for the determination of 20 and 50 µg L^-1Cd(II) respectively. The limits of detection obtained are 1.038 and 0.57 µg L^-1for 60 s and 120 s sorption time respectively. A sample throughput of 32 h^-1 is obtained with 5 mL of sample solution. Spiked recovery studies in water samples with certified Cd(II) nitrate solution traceable to NIST shows recovery in the range of 98-99 %. The accuracy of the developed online FI-FAAS procedure has been validated by analyzing cadmium(II) in standard reference material (SRM-1643e).

Page(s): 1567-1573