Modification of the electroosmotic flow and separation selectivity of anions in electrochromatography with pseudo-stationary phases of C14-alkyldimethylammoniopropane sulfonate zwitterionic surfactants by addition of salts to the background electrolyte

Abstract

The effects of salts (NaCl, NaClO4, MgCl2, CeCl3) added to background electrolyte (BGE) solutions (10 mmol L(-1) sodium phosphate, pH 7.2) on electroosmotic flow (EOF) and the separation selectivity of anions (chloride, bromide, iodide, nitrite, nitrate, chlorate, thiocyanate, iodate, chromate, and molybdate ion) by capillary electrochromatography using the zwitterionic surfactant 3-(N,N-dimethylmyristylammonio)propane sulfonate (C14N3S) as a pseudo-stationary phase were investigated. There are two mechanisms affecting the separations: 1. the cations and anions of the added salts interact with the zwitterionic surfactant to varying degrees, thus changing the overall retention of the analytes; and 2. they change the EOF and the resulting apparent mobilities. It was shown that a BGE containing perchlorate and a low concentration of zwitterionic surfactant (2 mmol L(-1)) gave a stable and reproducible EOF and the concentration of perchlorate could be used to manipulate the separation selectivity for polarizable anions, such as iodide and thiocyanate. These effects are discussed in terms of measured association constants describing the interaction of anions and cations with the zwitterion.

Protonated diamines as anion‐binding agents and their utility in capillary electrophoresis separations

“…MEKC utilizes the partitioning of solutes between the solution and micellar phases. Often, partitioning in MEKC is dictated by analyte hydrophobicity; thus, as with pH tuning, this technique is traditionally most useful for organic species with few examples published for inorganic ions 12–15.…”

Application of dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium in wall modification for capillary electrophoresis separation of proteins

“…However, inorganic anions are usually difficult to separate with native silica capillaries because of the opposite electrophoretic movement of anions, unless very high salt concentration [32] and very low pH are used to suppress the EOF [29]. Cationic surfactants [33] and zwitterionic surfactants [31,32,39,40] have been used to improve the separations of inorganic anions. Here, the separation conditions for a mixture of inorganic anions in the presence of the dynamic additive DSB were optimized.…”

Separation of multiply charged anions by capillary electrophoresis using alkyl phosphonium pairing agents

“…Noteworthy are the zwitterionic surfactant additives. They possess interesting properties as they adsorb on the inner surface of the capillary wall and suppress EOF without inducing its reversal [].…”