Prediction of the separation of phenols by capillary zone electrophoresis (original) (raw)
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Effect of cationic polymer on the separation of phenols by capillary electrophoresis
Journal of Chromatography A, 1997
The capillary electrophoretic separation of substituted phenols was examined using high-molecular-mass polyethyleneimine (PEI) as a buffer additive. The added PEI to the running buffer showed a strong interaction with the phenols and affected the electrophoretic mobilities and migration order of phenols. The influence of pH, organic solvent and concentration of polyelectrolyte on the electrophoretic mobilities of analytes was investigated.
Separation of Priority Pollutant Phenols with Coelectroosmotic Capillary Electrophoresis
Analytical Chemistry, 1997
Various mixtures of phenolic compounds, most of them being priority pollutant phenols, are separated by coelectroosmotic capillary electrophoresis. To obtain short separation times a codirectional movement of the anionic phenolates and the electroosmotic flow (EOF) is established by adding a polycationic EOF modifier to the alkaline buffer electrolyte. To increase the selectivity of the separation and the resolution between the solutes, organic solvent mixtures are added to the separation buffer. Furthermore, coelectroosmotic MECC of phenols using cetyltrimethylammonium bromide (CTAB) as pseudostationary phase and acetonitrile as organic modifier is performed. The developed methods are used for the fast separation of the 9 cresol and xylenol isomers, as well as mixtures of 18 chlorophenols, 11 phenols (acid extractable mixture, EPA M-625A), and 9 phenols (EPA M-8040B-R). Separation mechanisms are discussed on the basis of solvation effects of the phenolic solutes. In the case of CTAB-MECC the influence of the CTAB concentration and of acetonitrile on the solubilization of the phenols is investigated.
Separation of acidic solutes by nonaqueous capillary electrophoresis in acetonitrile-based media
Journal of Chromatography A, 2000
Nonaqueous capillary electrophoresis (NACE) is a chemical separation technique that has grown in popularity over the past few years. In this report, we focus on the combination of heteroconjugation and deprotonation in the NACE separation of phenols using acetonitrile (ACN) as the buffer solvent. By preparing various dilute buffers consisting of carboxylic acids and tetrabutylammonium hydroxide in ACN, selectivity may be manipulated based on a solute's dissociation constant as well as its ability to form heterogeneous ions with the buffer components. ACN's low viscosity, coupled with its ability to allow for heteroconjugation, often leads to rapid and efficient separations that are not possible in aqueous media. In this report, equations are derived showing the dependence of mobility on various factors, including the pK of the analyte, the pH and a f concentration of the buffer, and the analyte-buffer heteroconjugation constant (K ). The validity of these equations is tested f as several nitrophenols are separated at different pH values and concentrations. Using nonlinear regression, the K values for the heteroconjugate formation between the nitrophenols and several carboxylate anions are calculated. Also presented in this report are the NACE separations of the 19 chlorophenol congeners and the 11 priority pollutant phenols (used in US Environmental Protection Agency methods 604, 625 / 1625 and 8270B).
Capillary electrophoresis of methyl-substituted phenols in acetonitrile
Journal of Chromatography A, 2003
The separation of mono-and dimethylphenols by capillary electrophoresis in pure acetonitrile was investigated. In acetonitrile, uncharged phenols interact with background electrolyte anions forming negatively charged complexes, which can be separated from each other by capillary electrophoresis. The background electrolyte anions tested were acetate, bromide and chloride. The calculated formation constants for phenol-anion complexes were highest with acetate and smallest with bromide. Complex formation was found to be sensitive to traces of water in the background electrolyte. The separation of methylphenols was also carried out in acetonitrile at high pH using background electrolytes prepared from diprotic acids and tetrabutylammonium hydroxide. At high pH the phenols were partly dissociated, providing an additional mechanism for the separation. All methylphenols were separated with the use of malonate background electrolyte. However, this approach was prone to interference from methanol resulting from the tetrabutylammonium hydroxide solution.
ELECTROPHORESIS, 2006
A new method for the electrophoretic separation of nine phenolic acids (derivatives of benzoic and cinnamic acids) with contactless conductometric detection is presented. Based on theoretical calculations, in which the mobility of the electrolyte co-and counterions and mobility of analytes are taken into consideration, the electrolyte composition and detection mode was selected. This approach was found to be especially valuable for optimization of the electrolyte composition for the separation of analytes having medium mobility. Indirect conductometric detection mode was superior to the direct mode as predicted theoretically. The best performance was achieved with 150 mM 2-amino-2-methylpropanol electrolyte at pH 11.6. The separation was carried out in a counter-electroosmotic mode and completed in less than 6 min. The LODs achieved were about 2.3-3.3 mM and could be further improved to 0.12-0.17 mM by using a sample stacking procedure. The method compares well to the UV-Vis detection.
ELECTROPHORESIS, 2003
A mixture of methyl-and hydroxy-substituted phenols was separated by capillary electrophoresis in pure acetonitrile and propylene carbonate. Interactions between undissociated phenolic compounds and the background electrolytes were investigated. In the present work, benzyltriethylammonium chloride, tetrabutylammonium acetate, and two room temperature-molten salts, 1-butyl-3-methyl imidazolium trifluoroacetate and 1-butyl-3-methyl imidazolium heptafluorobutanoate, were used as background electrolytes. The formation of a negative complex between background electrolyte anion and neutral phenolic compound was observed and the formation constant calculated. The formation constants for anion-analyte complexes were approximately the same in propylene carbonate and in acetonitrile. In both solvents the formation constants were the highest for acetate and the lowest for trifluoroacetate. The separation of analytes was slightly influenced by the nature of the solvent: in acetonitrile the resolution between peaks was higher for 1,3-dihydroxyphenol and 1,3,5-trihydroxyphenol, in propylene carbonate 3-methylphenol and phenol were better separated. It was demonstrated that traces of water influence the mobilities of anion-phenol complexes in propylene carbonate.
Electroanalytical Method for The Detection of Phenol: A Brief
Phenolic compounds are the most common species found in plants, agro-food matrices, and biological samples. Many conventional and advanced techniques, such as cyclic voltammetry and enzyme-based biosensor, are available to detect phenolics from complex matrices. However, detecting the low concentration of phenolics in complex matrices is challenging. Among them, the electroanalytical method is rapid and allows us to detect phenolics from hazardous organic compounds and biological sources. This method offers high selectivity and low detection limits in determining phenolics contaminants. In this brief, the mechanism of electrochemistry, along with voltammetry, is discussed.
Electrochemical detection of phenol in aqueous solutions
Phenol oxidation in aqueous solutions was carried out in a pH range of 7-12 using cyclic votlammetry (CV) and differential pulse voltammetry (DPV) studies on a glassy carbon electrode. Peak potentials are found to be distinct for each pH value. A linear relationship is observed between the peak current and the concentration ranging from micro-to millimolar levels. The peak current is found to be proportional to the concentration of phenol up to 5 μM that allows determination of unknown concentrations of phenol down to 5 μM. Using DPV technique, the phenol concentration is detected up to a concentration of 0.5 μM.