Al(III) complexation by alizarin studied by electronic spectroscopy and quantum chemical calculations

Sorption of alkaline earth metal ions Ca2+ and Mg2+ on lyocell fibres

Separation of 9,10-anthraquinone derivatives: evaluation of C18 stationary phases.

A method was recently developed to determine the conditional stability constant, Kf′, using ion chromatography (IC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS) (C. Huang and D. Beauchemin, J. Anal. At. Spectrom., 2006, 21, 317–320 and C. Huang, D. Beauchemin, J. Anal. At. Spectrom., 2006, 21, 1419–1422).1,2 It involves the separation of a metal complex from the free metal ion by ion exchange with on-line detection of eluting metal-containing species by ICP-MS. The relative amounts of the complexed and free metals were simply obtained from the area of the corresponding peaks in the time-resolved chromatograms. A plot of the logarithm of the peak area ratio of the complex over the free metal as a function of the logarithm of the analytical concentration of the ligand gave log Kf′ as the intercept and the chelation number, n, as the slope. Although this method was demonstrated to allow the accurate determination of the conditional stability constant of a simple system (EDTA complexes of Co and Zn),1,2 the corresponding chelation numbers were significantly off from the expected unity value. A close scrutiny of the method revealed the main source of the discrepancy: it assumed that the ligand was in excess, which was not the case. Furthermore, it neglected other complexes than that with EDTA4−, such as those with HEDTA3−, H2EDTA2−, etc. In this work, no asuumption is made and a linear regression of the logarithm of the peak area ratio of the complex over the free metal versus the logarithm of the concentration of the uncomplexed chelating reagent is shown to accurately give both log Kf′ as the intercept and the chelation number as the slope. This revised method was successfully applied to Co-EDTA and Zn-EDTA complex systems with 0.1 M NH4NO3 as the supporting electrolyte.

Determination of stability constants of metal complexes with IC-ICP-MS

............................................................................................................... viii I INTRODUÇÃO ..................................................................................................... 1 I.1 Complexos metálicos ................................................................................ 1 I.2 Aspectos gerais .......................................................................................... 3 I.2.a Ferro ............................................................................................. 3 I.2.b Azoteto .......................................................................................... 4 I.2.c Tetraidrofurano ........................................................................... 5 I.2.d Acetona ......................................................................................... 6 I.2.e Dioxano ......................................................................................... 6 I.3 Constantes de estabilidade ou de formação ........................................... 7 I.4 Constantes de estabilidade condicionais ................................................. 8 I.5 Funções empregadas na determinação de constantes de estabilidade . 9 I.5.a Número médio de ligantes ........................................................... 9 I.5.b Grau de complexação .................................................................. 10 I.5.c Método gráfico de Leden ............................................................. 11 I.5.d Grau de formação da espécie ..................................................... 12 I.6 Determinação experimental de constantes de estabilidade .................. 13 I.7 Considerações gerais sobre métodos indiretos ....................................... 14 II OBJETIVOS ......................................................................................................... 17

Estudo potenciométrico sobre a formação de complexos no sistema ferro (III)/azoteto, em meio não totalmente aquoso

The Determination of Stability Constants of Para Substituted N-Benzylideneaniline Metal Complexes by a Potentiometric Method

Alizarin, which consists of 1,2 dihydroxyanthraquinone, is the common madder of anthraquinoid pigment group. It has been used for textiles, food and medicine. The colour of alizarin is light brown and dissociates low in water. It is in the root of Rubia tinctorum plant. The plant is 50-80 cm high and its trunk is cornered, hard and thorny. In the present study a Potentiometrie titration and spectrophotometric method has been used to determine stability constants for Mg(II) and Al(III) with alizarin. Stability constants of binary system have been evaluated by the method suggested by Irving -Rossotti procedure. The protonation and acid constants at 25 °C have been found as follows: LogK,= pK2 =8,09 LogK2=pK,= 5,91 The conditional formation constants of the formed complexes were calculated and pH ranges through which the complexation occurs were found. Magnesium (II)-Alizarin: LogK,=4,96 ; K,= 9,12. 10 Aluminium(II)-Alizarin: LogK,= 10,88 ; K,= 7,586. 10 LogK2=10,31 ; K2= 2,042. 10 In addition, the conditional constants were calculated as a function of pH. The maximum values of the conditional formation constants were found to be in accordance with the metal ligand complexes formation constants in a given

The Determination of the Stability Constants Binary Complexes of Alizarin with Mg (II) and Al(III) by Potentiometrie and Spectrophotometric Methods

Titration potentiometry and spectrophotometry have both been used to determine stability constants for mixed complexes of Cu(II) with creatinine and EDTA. Stability constants of the ternary system were evaluated by a method suggested by the Irving-Rossotti procedure. Conditional constants were established as a function of pH; the maximum values of the conditional formation constants were found to be in agreement with the mixed-ligand complex formation constants in a given pH region. The mole fractions of mixed complexes were calculated using the formation constants. The stability constants of mixed-ligand complexes at 25°C are: log K| = 5.29, log K2 = 4.97, with ionic strength being kept constant at I = 0.1 with NaC104. Also, Cu(II)-I-glutamic acid-creatinine and Cu(II)-EDTA-creatinine complex formation, as examined by the spectrophotometric method, gave results that were in agreement with those of the Potentiometrie method. K e y w o r d s : creatinine, EDTA, 1-glutamic acid, copper(II) complexes, mixed complex, stability constants.

DETERMINATION OF STABILITY CONSTANTS OF MIXED LIGAND COMPLEXES OF Cu(II) WITH CREATININE AND ETHYLENEDIAMINE TETRAACETIC ACID OR I-GLUTAMIC ACID: POTENTIOMETRIC AND SPECTROPHOTOMETRIC METHODS

Serap Karaderi

Papers

The Determination of Stability Constants of Para Substituted N-Benzylideneaniline Metal Complexes by a Potentiometric Method

The Determination of the Stability Constants Binary Complexes of Alizarin with Mg (II) and Al(III) by Potentiometrie and Spectrophotometric Methods

DETERMINATION OF STABILITY CONSTANTS OF MIXED LIGAND COMPLEXES OF Cu(II) WITH CREATININE AND ETHYLENEDIAMINE TETRAACETIC ACID OR I-GLUTAMIC ACID: POTENTIOMETRIC AND SPECTROPHOTOMETRIC METHODS