摘要:

The first and second protonation constant (logβ111,logβ121) of the metal-ligand complex Gadolinium(III)-diethyltriamine-pentaacetic acid (DTPA) have been determined to be 2.27 and 1.52 at 25 °C and I = 0.1. A technique in which the three complexes (H2Gd-DTPA, HGd-DTPA−1, Gd-DTPA−2) are separated according to their relative polarity is utilized. An inductively coupled plasma-atomic emission spectrometer (ICP-AES) is used to determine the relative concentrations of each species by monitoring the gadolinium concentration.

ISSN:0038-7010    

DOI:10.1080/00387019909349998

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Stabilization of sulfide as zinc sulfide is a strategy widely used in batch analysis of this ion in water. A FIA/spectrophotometry system to determine sulfide in stabilized water samples is proposed in this paper. The methodology is based on the formation of methylene blue by the reaction of H2S with a mixture of Fe3+solution and N,N-dimethyl-p-phenylenediamine (DMPD) in acidic medium. In the system, the sample (480 μL) containing stabilized sulfide (as ZnS slurry) is injected in a carrier stream formed by mixing acidic Fe3+and DMPD. In the reactor coil of 1280 μL, the sulfide is drifted by acid used in the preparation of solutions, releasing H2S that reacts with Fe3+and DMPD forming methylene blue. The absorbance is measured at 662 nm. The performance of the FIA system was optimized in relation to chemical and flow parameters. The stability of the solutions were studied throughout the period of the experiment. The results did not show any loss of sulfide over a 7 day period. However, in complex matrices an analysis by using the standard addition method is recommended. The analysis of effluent sample through the time showed good agreement between the results obtained each day. The developed system presented the following figures of merit: detection limit of 50 μg L−1; RSD of 6% at 0.5 μg mL−1(using ultrasonic homogenization) and analytical throughput of 60 samples per hour.

ISSN:0038-7010    

DOI:10.1080/00387019909349999

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

New substituted N- (2,6-Di-tert-butyl-l-hydroxyphenyl) Salicylaldimines (LxH) were prepared by the condensation of various hydroxy and methoxy salicylaldehyde derivatives and 2,6-Di-tert-butyl-4-aminophenol and characterized by elemental analysis, IR, UV-Vis,1H NMR spectroscopy, as well as ESR studies of the oxidation products of LxH. It was found that LxH, unlike analogous electron-withdrawing C1, Br, NO2bearing derivatives, in the solid state exist both in associated and non-associated forms. UV-Vis and1H, NMR studies show that LxH in solutions exists both in phenolimine and ketoamine tautomer forms. In addition, alcohol solutions of LxH exhibited a new band in the region of 630-675 run. The ESR studies of one -electron oxidation of LxH, in the condition of THF, CHC13and toluene solutions at 300 K, indicate the formation of corresponding primary or secondary phenoxyl radicals. It was found that the stability and conversion pathway of the primary phenoxyl radicals are dependent upon both kind and position of the substituents in salicylaldehyde moiety of LxH. For some LxH without observation of primary phenoxyl radicals, the secondary Coppinger's type radical was detected. The ESR parameters of all radical intermediates have been determined.

ISSN:0038-7010    

DOI:10.1080/00387019909350000

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The halochromic behaviour of the title ruthenium complex in acetonitrile and dimethylformamide, in the presence of lithium, sodium and magnesium perchlorate, was studied employing parallel spectroscopic and voltammetric measurements. The results point to an association between the added cation and the chloride ligands, that depends on the nature of the cation and of the solvent, and which affects the charge density on the central ruthenium metal.

ISSN:0038-7010    

DOI:10.1080/00387019909350001

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor