Investigation of salicylaldehyde-5-sulfonate as a precolumn derivatizing agent for the determination of n-alkane diamines, lysine, diaminopimelic acid, and isoniazid by capillary zone electrophoresis.

Reactions of primary amines with salicylaldehyde-5-sulfonate (SAS) lead to the formation of stable Schiff bases at weakly alkaline pH and at moderate temperature in an ethanol-rich aqueous solution. Some alkane diamines were converted to salicylaldimine with SAS, and the products were resolved and detected by capillary zone electrophoresis (CZE). The reactivity of SAS was applied also to the derivatization of amino acids. Optimal conditions for the analysis of lysine in the presence of diaminopimelic acid, the metabolite of lysine, were investigated. Addition of Na(2)SO(4) into the migrating solution enhanced the stacking effect, and led to increase in the detection limits. Another advantage of the use of SAS is its ability to form stable water-soluble metal chelate as Schiff base ligands. For practical analysis, the copper chelate of the Schiff base of isoniazid, which is known as the most active antibacterial used in the treatment of pulmonary tuberculoses, was investigated, and the detection limit of isoniazid was improved in the magnitude of 11 times compared with the one of free isoniazid.