Separation of naphthalenesulfonate isomers by capillary zone electrophoresis using macrocyclic polyamines as additive for running solution

Abstract

The separation of naphthalenesulfonate (NS) isomers has been successfully performed by capillary zone electrophoresis using macrocyclic polyamines, such as [9]aneN₃ and [14]aneN₄, as an additive to the running solution. Although group separation between naphthalenemonosulfonates (mono-NSs) and naphthalenedisulfonates (di-NSs) was achieved, the separation between mono-NS isomers, 1-NS and 2-NS, and the separation among di-NS isomers, 1,5-NS, 1,6-NS, 2,6-NS and 2,7-NS, could not be achieved using a hydrochloric acid solution (pH 2.0) as the running solution. The addition of [14]aneN₄ to the running solution (pH 2.0) gave good separation, not only between mono-NSs and di-NSs but also among their NS isomers. The sequence of elution time increased in the order 2,6-NS < 2,7-NS < 1,6-NS < 1,5-NS < 2-NS < 1-NS. The sequence of elution time indicates that the interaction of the NSs with [14]aneN₄ increases in the order 2,6-NS < 2,7-NS < 1,6-NS < 1,5-NS for the di-NS isomers and 2-NS < 1-NS for the mono-NS isomers. A similar sequence of elution time was obtained when [9]aneN₃ was used as the additive, although the separations between the 1,5- and 1,6-NS isomers and 1- and 2-NS isomers was not complete. The elution sequence and the separation efficiency among the NS isomers are discussed with reference to the molecular structures of the macrocyclic polyamines and the NS isomers.