Optimization of pH for the separation of organic acids in capillary zone electrophoresis

Abstract

The migration behavior and optimum separation of a set of substituted phenols is presented. A mathematical model that describes mobility in CZE in terms of fundamental constants of each solute (acid dissociation constant Ka, mobility of the dissociated acid microA-) and the pH of the buffer was used to predict the mobility of each solute as a function of pH. The resolution between each peak pair was calculated, and a window diagram of minimum resolution as a function of pH was employed in determining the optimum pH. A comparison of the predicted and actual electropherograms shows the usefulness of this technique.

Quantification of Methylmalonic Acid in Human Plasma with Hydrophilic Interaction Liquid Chromatography Separation and Mass Spectrometric Detection

“…From these pK a values for the 2 carboxylic groups of MMA and SA, we expected a mobile-phase pH in the interval between pH 3 and pH 5 to be optimal for separation (10,26 ). pK a values may change in mixtures of aqueous and organic solvents, however, and are difficult to predict (27 ). Therefore, we started at pH 6.8 and observed 2 separated peaks at baseline with the same m/z ratio of 117, which corresponded to MMA and SA.…”

Relation between Electrophoretic Behavior and Molecular Shapes of Aromatic Anions

“…17,18 In addition, a simulation of the µep values with the pH and the 2-hydroxyisobutyric acid (HIBA) concentration of the buffer has been reported for metal HIBA complex ions. 19 The effects of the µep values on a number of water-soluble organic solvents (such as methanol) for aromatic carboxylates with various functional groups (such as hydroxyl groups) have been reported.…”

“…8 In addition, a number of methods of predicting µep have been reported. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] The molecular weights (MW) have been reported to correspond to the µep values for amides. [9][10][11][12][13][14] In addition, for some organic and metal complex ions, the MWs correspond to the µep values.…”

“…17,18 In addition, a simulation of the µep values with the pH and the 2-hydroxyisobutyric acid (HIBA) concentration of the buffer has been reported for metal HIBA complex ions.…”

Statistical data processing of mobility curves of univalent weak bases

“…They were developed to circumvent the above-mentioned drawbacks of the linearized forms. Most of them are based on the use of the Boltzman sigmoidal decay function [5,11,[16][17][18] and, especially on its special form called exponential form of electrophoretic Henderson-Hasselbach equation [7,[19][20][21]. For weak bases it is:…”