Poly(vinylamine)-coated capillaries with reversed electroosmotic flow for the separation of organic anions

This paper describes the chemistry presented during the W.A.E. McBryde Medal address given at the 81st Chemistry in Canada Conference held in Whistler. The narrative chronicles our Quest to perform isotopic separations in the solution phase using as our Excalibur, capillary zone electrophoresis. The narrative takes you through the highs of our early success in separating 35Cl- and 37Cl-. This separation was achieved by adjusting the electroosmotic flow to be equal in magnitude but opposite in direction to the chloride mobility. The narrative then takes you through the dark days, when we could not extend the isotopic separations to cationic species or even explain why there was an isotopic effect on mobility. Since those dark days, we have made numerous discoveries that have aided our Quest. Firstly, the development of mixed surfactant wall coating procedures yielded control of the reversed electroosmotic flow. This control enabled us to perform isotopic separations of systems such as 15N-/14N-aniline and 15NH4+/14NH4+. In terms of understanding electrophoretic mobility, we demonstrate the importance of dielectric friction to mobility. Further, the effect of ionic strength in capillary zone electrophoresis is explained using the Pitts treatment, which is analogous to the extended Debye-Hückel equation for ionic activity. So, have we completed our Quest? Read on.Key words: capillary zone electrophoresis, isotopic, electroosmotic flow, mobility modeling, ionic strength.

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Control of relative migration of small inorganic and organic anions with cyclodextrins in capillary electrophoresis (CE)

Canadian Journal of Chemistry ◽

10.1139/v97-230 ◽

1998 ◽

Vol 76 (2) ◽

pp. 194-198

Author(s):

Costas Stathakis ◽

Richard M Cassidy

Keyword(s):

Capillary Electrophoresis ◽

Electroosmotic Flow ◽

Organic Anions ◽

Sodium Chromate ◽

Migration Patterns ◽

Electrophoretic Mobilities ◽

Potassium Hydrogen ◽

Capillary Electrophoretic ◽

Relative Migration ◽

Inorganic And Organic

The capillary electrophoretic separation of iodide, nitrate, perchlorate, thiocyanate, bromate, iodate, and ethane-, butane-, pentane-, and octanesulphonate was examined in sodium chromate or potassium hydrogen phthalate electrolytes and in the presence of α -, γ -, (0-40 mmol/L) and β -cyclodextrin (0-10 mmol/L). Largest decreases in electrophoretic mobility were observed for iodide, perchlorate, and thiocyanate, probably due to inclusion of these anions in the cyclodextrin (CD) cavity. Changes in migration patterns and electroosmotic flow were observed, which depended on cyclodextrin type and concentration and on electrolyte-cyclodextrin interactions. Thus for larger cavity cyclodextrins ( β-or γ-cyclodextrin) or in the presence of chromate, relatively small decreases in electrophoretic mobilities for all the anions were observed, indicating that a good match between analyte and cavity size and minimal cyclodextrin affinity for electrolyte ions are essential for different migration patterns. Separation efficiencies were between 50 000 and 400 000 theoretical plates, and calibration plots for iodide and octanesulphonate were linear; R2 = 0.998 and 0.9999, respectively, in the concentration range (5 x 10-5)-(5 x 10-3) mol/L.Key words: capillary electrophoresis, inorganic and organic anions, cyclodextrins, inclusion complex, electroosmotic flow control.

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