Separation of Priority Pollutant Phenols with Coelectroosmotic Capillary Electrophoresis

Abstract

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 pseudo-stationary 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 Pollutant Phenols by Micellar Electrokinetic Chromatography with Double-Chain Surfactants Having Two Sulfonate Groups

“…Pentachlorophenol and 2,4,6-trichlorophenol have pK a values of 4.93 and 6.51, respectively. 12 Therefore, these changes in the capacity factors in the pH range 6 -8 are reasonably interpreted by their acidity constant values. This observation is in agreement with that reported by Otsuka et al 17 The capacity factors of the other phenols were insensitive to pH in the range of 6 -8 except for 2-and 4-nitrophenol whose capacity factors slightly increased at pH 8.0.…”

“…This irregularity of 2,4-dinitrophenol and 2-methyl-4,6-dinitrophenol may be ascribed to their low pK a values of 4.08 and 4.34, respectively. 12 The separation of EPA phenols with three surfactants was carried out at surfactant concentrations between 3 -10 mM in the separation buffer at pH 7.0. Typical chromatograms for the separations of the phenols are shown in Fig.…”

“…[7][8][9][10] Both CZE and MEKC have also been employed for the separation of certain phenols. 2,11,12 In previous papers [13][14][15] , we introduced one triple-chain and five double-chain surfactants having two sulfonate or two carboxylate groups. For the separation of several benzene, naphthalene and flavone derivatives as model analytes, these surfactants exhibited a remarkably different MEKC selectivity, wider migration time windows and the separation performance at concentrations at least one order of magnitude lower, in comparison with sodium dodecyl sulfate (SDS), a widely used surfactant with one sulfate group and one lipophilic chain.…”

Applicability of Micellar Electrokinetic Chromatography with a Double-Chain Surfactant Having Two Sulfonate Groups to the Determination of Pollutant Phenols in Water

“…Along with capillary-zone electrophoresis, MEKC has also been employed to separate certain phenols. 9,10 To our knowledge, the eleven priority phenols (EPA phenols) cannot be completely separated in HPLC. In a previous paper, 11 we described the complete baseline separation of EPA phenols by MEKC with a double-chain surfactant having two sulfonate groups: disodium 5,13-bis(dodecyloxymethyl)-4,7,11,14-tetraoxa-1,17-heptadecanedisulfonate (DBTHP).…”

Separation of Chlorophenols by Capillary Zone Electrophoresis. The Influence of pH of the Electrophoretic Buffer on Selectivity

“…Recently, their separation by capillary electrophoresis (CE) in different modes has attracted interest because CE is a rapid, powerful, and efficient separation method [9 -22]. Micellar electrokinetic chromatography (MEKC) has been recommended for separation of all chlorophenols [14,23], but separation by capillary zone electrophoresis (CZE) using organic modifiers in the respective buffer is also feasible [21]. The presence of organic modifiers is essential for preventing self-association of phenols and for solubilization in the buffer medium, but the most important parameter for adjustment of selectivity is pH.…”