Cationic Polymers for Selectivity Control in the Capillary Electrophoretic Separation of Inorganic Anions

Abstract

The capillary electrophoretic (CE) separation of the inorganic anions bromide, chloride, nitrate, nitrite, fluoride, sulfate and phosphate is described in 0.005 mol/L sodium chromate electrolyte in the presence of soluble polydisperse ionic polymers (polyelectrolytes). The cationic polyelectrolytes used were as follows: poly(1,1-dimethyl-3,5-dimethylenepiperidinium) chromate, hexadimethrine chromate, poly(1,1-dimethyl-3,5-dimethylenepyrrolidinium) chromate and ((diethylamino)ethyl)-dextran chromate in the concentration range 0.004-0.6% (w/v). These polyelectrolytes were shown to be capable of reversing the direction of the electroosmotic flow as well as inducing changes in analyte electrophoretic mobility, separation selectivity, and resolution. Changes in electrophoretic mobility by as much as 25% were observed for the sulfate anion, and the resolution of fluoride and phosphate was enhanced by a factor of 7.8. In the presence of 0.05-0.17% w/v poly(1,1-dimethyl-3,5-dimethylenepyrrolidinium) chromate at pH 8, separation currents were found to increase only slightly as compared to an electrolyte containing equivalent amounts of sodium chromate. Electroosmotic flow was also found to be fairly constant (+/- 16%) in the pH range 6.55-10.02 for 0.01% (w/v) poly(1,1-dimethyl-3,5-dimethylenepiperidinium) chromate at an ionic strength of 0.04, compared to a 400% change in the absence of the polyelectrolyte. The reproducibility of the electroosmotic mobility was between 0.36 and 6% RSD, and analyte electrophoretic mobility was between 0.01 and 1.6% RSD. Peak height reproducibility was 0.2-8.0% RSD. Separation efficiencies were between 258,000 and 780,000 theoretical plates, and detection limits were between 4.4 x 10(-7) and 9.1 x 10(-6) mol/L.

Selectivity change in the separation of proteins and peptides by capillary electrophoresis using high-molecular-mass polyethyleneimine

“…Following this idea, Stathakis and Cassidy proposed cationic polymers for selectivity control in the CE separations of inorganic anions [19]. This enables different selectivity control from that normally employed, i.e., variation of the buffer pH, and the use of complexing or ion-pairing agents for the separation of small ions.…”

Towards a microchip‐based chromatographic platform. Part 2: Sol‐gel phases modified with polyelectrolyte multilayers for capillary electrochromatography

“…The use of polyelectrolytes in CE was established in the early 90's for EOF control and as a pseudophase in ionexchange electrokinetic chromatography [35][36][37][38]. While this approach has been used extensively for EOF control (readers are directed to a recent review on polymeric coatings for more details [20]), the buildup of multiple layers of oppositely charged polymers has only recently been applied to CEC where it was shown to provide a very stable and reproducible coating [26][27][28].…”

Peer Reviewed: Selectivity in CE

“…Examples include 2,2,2-trifluoro ethanol, an organic solvent used for peptides (28); 1-hexanol, cyclohexanol, and phenol as organic modifiers for separating aromatic compounds by SDS-MEKC (23); poly(1,1-dimethyl-3, 5-dimethylenepiperidinium chloride), an ionic polymer used for small organic and inorganic cations (29); Brij-sulfon ate, a surfactant for neutral organics (11); partially hydro lyzed polyacrylamide, an ionic polymer for neutral organics (30); phytic acid for organic acids (31), peptides, and proteins (32); imprinted poly mers for chiral separations (33); proteins for a diversity of analytes, especially enantiomers (34); and sodium laurylsulfoacetate (LSA), a surfactant applied to neutral organics (35). Figure 4 shows a significant variation in selectivity between the use of SDS (ordinary) and LSA (exotic) micelles for the separation of aniline derivatives (35).…”