tolfenamic-acid and formamide

The electrophoretic mobility of selected acidic and basic test solutes have been determined in non-aqueous media prepared by adding various combinations of ammonium acetate, sodium acetate, methane sulphonic acid and acetic acid to acetonitrile, propylene carbonate, methanol, formamide, N-methylformamide, N,N-dimethylformamide and dimethylsulphoxide, respectively. The apparent pH (pH*) of these non-aqueous media have been measured and it was found that pH* is an important factor for the separations in non-aqueous capillary electrophoresis. However, in some solvents the concentration of sodium acetate has a strong influence on the mobility despite very small changes in pH*. Due to the fact that a change in one parameter influences a number of other parameters it is very difficult to conduct systematic studies in non-aqueous media and to compare the migration of the species at fixed pH* values from one solvent to another. Thus pH* is only of value for comparison when used with a specific solvent or solvent mixture. The viscosity of the above-mentioned solvents were measured at various temperatures and means to adjust the viscosity of the non-aqueous media used for capillary electrophoresis are discussed and the separation of ibuprofen and its major metabolites in urine is used as an example.

Topics: 4-Aminobenzoic Acid; Acetonitriles; Aminobenzoates; Carbonates; Desipramine; Dimethyl Sulfoxide; Dimethylformamide; Electrophoresis, Capillary; Formamides; Hydrogen-Ion Concentration; Ibuprofen; Imipramine; Methanol; Models, Statistical; Organic Chemicals; ortho-Aminobenzoates; Propane; Solvents; Temperature; Time Factors; Viscosity; Water