NOPR Collection:

Determination of Ni(II) and Co(II) by FAAS after preconcentration on modified alumina column

2003-05-01T00:00:00Z

Title: Determination of Ni(II) and Co(II) by FAAS after preconcentration on modified alumina column Authors: Shemirani, Farzaneh; Kozani, Reyhaneh Rahnama; Niasari, Masood Salavati; Abkenar, Shiva Dehghan; Jamali, Mohammad Reza; Mirroshandel, Aazam Alsadat Abstract: A method for the determination of Co(II) and Ni(II) by flame atomic absorption spectrometry after preconcentration on a minicolumn of alumina modified with sodium dodecyl sulfate and schiff's base has been developed. Effects of pH, flow rate, volume of sample solution, capacity of sorbent and interference of foreign ions on the recovery of the analytes have been investigated. Under the optimized conditions (pH = 5; flow rate =15 ml min^-1), recovery was greater than 98%. The relative standard deviations (10 replicate analyses) at the 50 ng ml^-1 level are 2.5% for Ni(II) and 3.2% for Co(II) and the corresponding limits of detection (3s, n =10) are 0.014 ngml^-1 for Ni(II) and 0.007 ng ml^-1 for Co(II). The method has been applied for the determination of Ni(II) and Co(II) in natural waters and standard materials. Page(s): 1086-1088

Spectrophotometric determination of protonation constant of N-phenylbenzohydroxamic acid in mineral acids

2003-05-01T00:00:00Z

Title: Spectrophotometric determination of protonation constant of N-phenylbenzohydroxamic acid in mineral acids Authors: Ghash, Kallal K; Tamrakar, Pankaj Abstract: The UV spectra of N-phenylbenzohydroxamic acid (C₆H₅CON(OH)C₆H₅) in sulphuric, perchloric and hydrochloric acid solutions have been analyzed by the characteristic vector method in order to separate protonation from the medium effect. Using the first vector coefficient values, proton at ion constant ( pK _BH⁺) and solvation parameters have been estimated. In the high acidity range, results obtained according to the Cox-Yates excess acidity function. Marziano Mc function, Bunnett-Olsen and Hammett-acidity function methods are in good agreement. Page(s): 1081-1085

La(III) complex of phenanthroline bridging polyamine as efficient catalyst for the hydrolysis of ATP

2003-05-01T00:00:00Z

Title: La(III) complex of phenanthroline bridging polyamine as efficient catalyst for the hydrolysis of ATP Authors: Guo, Yanhe; Ge, Qingchun; Lin, Hai; Lin, Huakuan; Zhu, Shourong Abstract: The hydrolysis of ATP catalyzed by protonated ligand 2, 9-di[(2'-ethylamino)ethylene-aminomethyl]-1, 10-phenanthroline·4HCl.H₂O(L) or its La(III) complex has been studied at pH 7.6 using ³¹P NMR spectroscopy. The two systems have a rate of 12.1×10^-4 mol.dm^-3 and 159×10^-4 mol.dm^-3 , which is about 5- and 59-fold as fast as that of free ATP respectively. La(III) complex of L is a more efficient catalyst for ATP hydrolysis than metal ion alone, which has a rate enhancement ratio about 5. High catalytic efficiency has been achieved through the effective activation of ATP by La(III) complex and the availability of a good intramolecular nucleophile. The phosphoramidate intermediate at 2.88 ppm in L/ATP system has not been observed in La(III)/L/ATP system. The mechanism for ATP hydrolysis catalyzed by complex of ‘‘hard’’ metal ion has been given. The effects of metal ion mediated by polyaza ligand in controlling the recognition of the substrate and the attacking on phosphorous counter have been discussed. Page(s): 1076-1080

Synthesis and crystal structures of N-(2,3,4,6-Tetra-O-acetyl-β-D-glycosyl)thiocarbamoyl methylene diamine

2003-05-01T00:00:00Z

Title: Synthesis and crystal structures of N-(2,3,4,6-Tetra-O-acetyl-β-D-glycosyl)thiocarbamoyl methylene diamine Authors: Jian, Fangfang; Wang, Huanxiang; Li, Yan; Zhang, Shusheng Abstract: The structure of N-(2,3,4,6-Tetra-O-acetyl-β-D-glycosyl)thiocarbamoyl methylene diamine, C₁₆H₂₅N₃O₉S has been determined by X-ray diffraction method. It crystallizes in the monoclinic system, space group P2_l, with lattice parameters a = 7.6560(2), b = 10.3113(3), c = 14.1813(1)Å, β = 100.879 (2)^o, and Z = 2. The hexapyranosyl ring adopts a chair conformation. All the ring substituents are in the equatorial position. The acetoxylmethyl group is in the gauche- gauche conformation. The S atom is in synperiplanar conformation, while the N-C-N-C linkage is antiperiplanar. The N-H^...O intermolecular hydrogen bonds link the molecules into infinite chains and these are connected by C-H^...O interaction. Page(s): 1072-1075