Carboxylic acids

This chapter discusses carboxylic acids that generally have high mobilities compared with those of proteins. Carboxylic acids used as model substances for checking both theoretical aspects and correct functioning of the equipment are separated qualitatively and quantitatively by isotachophoresis. Most electrophoretic work, except isotachophoresis is performed in equipment in which stabilizing media can be applied. Common isotachophoretic equipment makes use of narrow bore PTFE tubes with inside diameters of 0.2–0.6 mm. The separation of carboxylic acids qualitatively and quantitatively via moving boundary electrophoresis or ion focusing is less efficient in comparison to isotachophoresis. The analyses can be performed without sample pre-treatment in the column-coupling system or with a simple extraction and/or centrifugation. With the column-coupling system ionic substances at low concentrations in complex mixtures can be directly determined qualitatively and quantitatively. The urate-albumin complex is unstable under isotachophoretic conditions