Elucidation of Species in Alcohol-Water Mixtures Using Near-IR Spectroscopy and Multivariate Statistics

Alam, Mary Kathleen; Callis, James B.

doi:10.1021/ac00086a015

Cited by 60 publications

(63 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the other hand, except the results obtained by Alam and Callis [12], the other works indicated the presence of three major species in the methanol-water mixtures but they did not agree in the stoichiometry of the methanol-water associate. The inconsistency between the resulted association models for methanol-water mixtures demands extra efforts to more characterize this important binary solvent system.…”

Section: Introductionmentioning

confidence: 78%

See 1 more Smart Citation

Characterization and prediction of solute properties in methanol–water association by chemometrics analysis of solvation data

Hemmateenejad

2005

Journal of Chemometrics

View full text Add to dashboard Cite

Methanol-water binary mixtures have been characterized as a ternary or quaternary system composed of unassociated methanol (M) and water (W) and one or two methanol-water complex (MW). Identification of the methanol-water association was performed by chemometrics analysis of some solvent-related properties of binary methanol-water mixtures with compositions between 0 and 100% volume percent of methanol. Abstract factor analysis of the solvation data identified three chemical species in the solvent mixtures that can be attributed to the pure methanol and water solvents and a MW association. The stoichiometric molar ratio of the W:M associate was investigated by the multivariate curve resolution-alternative least squares (MCR-ALS) of the solvation data and the resulted concentration profiles of the solvent species implied a 1:1 molar ratio for the M:W association. The equilibrium constant of the formation of the M-W association was determined by MCR-ALS and iterative rank annihilation factor analysis (RAFA) to be equal to 13.72. The solvation data of the pure M-W cluster was calculated by target factor analysis (TFA) procedure. Higher hydrogen-bond basicity and lower hydrogen-bond acidity was obtained for the MW solvent in comparison with both the M and W solvents. The proposed model was employed to calculate the acidity constant and HPLC capacity factors of some solutes in the MW cluster. Interestingly, the solutes were found to be stronger acid in relative to pure methanol and water. Finally, the specific solute-solvent interactions and preferential solvation of the solutes were explained by the nonmodeled solute-related data.

show abstract

Section: Introductionmentioning

confidence: 78%

“…Alam and Callis [12] applied evolving factor analysis (EFA) and principal component analysis (PCA) on the second derivative near IR spectra of methanol-water mixtures. Number of factors thought to be three or four and therefore two chemical models, a single-associated model and a double-associated model, were considered.…”

Section: Introductionmentioning

confidence: 99%

Characterization and prediction of solute properties in methanol–water association by chemometrics analysis of solvation data

Hemmateenejad

2005

Journal of Chemometrics

View full text Add to dashboard Cite

show abstract

“…At lower pH these solutes tend to be less dissociated. In this way carboxy group of phenolic acids can participate in stable H-bond formation as proton donor, especially with MeOH (Alam and Callis 1994). However, concentration of methanol in the stationary phase region of MeOH system is considerably smaller than that of THF system (McCormick and Karger 1980;Gritti et al 2007).…”

Section: Methanol Vs Tetrahydrofuranmentioning

confidence: 99%

“…Phenolic acids are weakly or practically not dissociated in the mobile phase (pH 3.0). Then the carboxy group, under this condition (pH 3.0) as proton donor group, of each phenolic acid molecule can take part in formation of stronger complexes with methanol molecules in the stationary phase (Alam and Callis 1994). When pH of buffer in the mobile phase increases then the solutes are ionized to higher degree what leads to diminution of formation of the mentioned complexes.…”

Section: Acetonitrile Vs Methanolmentioning

confidence: 99%

Separation selectivity of some phenolic acids in RP HPLC systems with binary mobile phase comprised various modifiers

Klimek-Turek

Dzido

2010

Adsorption

View full text Add to dashboard Cite

Retention of phenolic acid has been correlated for reversed-phase high-performance liquid chromatography systems with different binary mobile phases containing methanol, acetonitrile or tetrahydrofuran as modifiers and buffer at pH 3.0, 4.6 and 5.0. The changes of separation selectivity of solutes, when one modifier is replaced by another in the eluent, has been explained taking into consideration molecular interactions of the solutes with components of the stationary phase region, i.e. extracted modifier, and ordering of the stationary phase by the modifier.Keywords Modifier selectivity · Mechanism of separation selectivity in reversed phase liquid chromatography · Phenolic acids

show abstract

“…This type of reaction is currently characterised by spectral techniques such as Infra-Red [1], Ultra-Violet [13] or NMR spectroscopy [9,11,12]. On the other hand, although variations in the TD-NMR relaxation rates as a function of degree of complexation has been proposed as a method for the determination of proteins [4,20], to to our knowledge this phenomenon has not yet been studied using chemometics.…”

mentioning

confidence: 99%

Complexation stoechiometry determined by application of chemometrics to time domain nuclear magnetic resonance signals

et al. 1998

View full text Add to dashboard Cite

The object of this study is to demonstrate the feasibility of using Time Domain-Nuclear Magnetic Resonance (TD-NMR) and multivariate statistical analysis techniques to determine the stoechiometry of complexations.This type of reaction is currently characterised by spectral techniques such as Infra-Red [1], Ultra-Violet [13] or NMR spectroscopy [9,11,12]. On the other hand, although variations in the TD-NMR relaxation rates as a function of degree of complexation has been proposed as a method for the determination of proteins [4,20], to to our knowledge this phenomenon has not yet been studied using chemometics. The TD-NMR technique is interesting from many point of view. It is non destructive and does not require the same specificity as U.V (being based on relaxation properties and not on the presence of chromophore groups). Furthermore, it requires a less expensive apparatus than does spectroscopic NMR.In a first step, the analyses are performed on parameters calculated from TD-NMR signals: longitudinal R 1 and transverse R 2 relaxation rates. In a second step, multivariate statistical analyses are applied directly to the TD-NMR signals themselves.To demonstrate the feasibility of using TD-NMR and multivariate statistical analysis in the study of stoechiometry of complexation reactions, we have chosen a very well characterised complex: manganese -EDTA (Ethylene Diamine TetraAcetate). Many studies [2,12,18] have been carried out showing that EDTA and manganese cations form a complex with stoechiometry 1:1.The basis of this study is the specific properties of paramagnetic compounds. Unpaired electrons in the external valence layer of a paramagnetic cation in solution in water create an electronic dipole/nuclear dipole interaction with the water protons. These interactions enhance the nuclear relaxation of the water leading to a significant increase in R 1 and R 2 values of the solution.In this study, aqueous manganate solutions were used. The relaxivity of manganese (capacity to relax the solvent protons) will be different depending on whether the manganese is free and directly solvated by water or complexed by the ligand where the external electrons will be paired to some extent leading to a loss of part of the paramagnetic properties of the manganese cation. Furthermore, the ligands around the cations limit the direct contact with the water molecules. In other words, if the solutions contain free manganate, the R 1 and R 2 values should be very high whereas they will be much lower if the manganese cation is complexed by a ligand.The ligand chosen to complex with manganese is EDTA (Ethylene Diamine Tetra Acetic acid): (HOOCCH 2 ) 2 N-CH 2 -CH 2 -N(CH 2 -COOH) 2 . In fact, this molecule has been studied very often and is known to complex 62 different metal cations with a 1:1 stoechiometry [12,18]. Its dissociation constant with manganese is 10 -13 mol -1 [5].To avoid any possible formation of Mn(OH) 2 , solutions were maintained at constant pH of 4.4 by a buffer solution of potassium hydrogenophthalate/sodium hyd...

show abstract

Elucidation of Species in Alcohol-Water Mixtures Using Near-IR Spectroscopy and Multivariate Statistics

Cited by 60 publications

References 24 publications

Characterization and prediction of solute properties in methanol–water association by chemometrics analysis of solvation data

Characterization and prediction of solute properties in methanol–water association by chemometrics analysis of solvation data

Separation selectivity of some phenolic acids in RP HPLC systems with binary mobile phase comprised various modifiers

Complexation stoechiometry determined by application of chemometrics to time domain nuclear magnetic resonance signals

Contact Info

Product

Resources

About