Spectrophotometric determination of 6-aminopenicillanic and 7-aminocephalosporanic acids as the Schiff bases with para-dimethylaminobenzaldehyde in the presence of sodium dodecyl sulfate micelles.

Yields of colored Schiff base products of the reversible condensation of 6-aminopenicillanic and 7-aminocephalosporanic acids with para-dimethylaminobenzaldehyde in a weakly acid aqueous solution strongly increase in the presence of micelles of sodium dodecyl sulfate. The binding constants of reactants and products of both reactions to micelles were calculated from the concentration profiles of micellar effects on rates and equilibrium of the condensation reactions. The observed micellar-induced shifts of equilibrium are accompanied by strong acceleration of the forward and small retardation of backward processes. Some deviations from the theoretical profiles due to saturation of micelles with reactants were observed. The colored form of the reaction product was found to be the protonated Schiff base. Its stability in time is strongly enhanced in the micellar medium. The spectrophotometric determination of title compounds under optimum micellar conditions possesses ca. 300 times higher sensitivity than the standard procedure.