resorcinarene and cyclen

The selectivity and separation of transition metal ions on two columns packed with cyclen-based macrocycles adsorbed onto 55% cross-linked styrene-divinylbenzene resin are presented. The N-cyclen and cyclen-resorcinarene stationary phases were made by adsorbing hydrophobically substituted N-cyclen or a cyclen-resorcinarene derivative (cyclenbowl) on the resin, respectively. The stability constants of cyclen with transition metal ions demonstrate that cyclen has selectivity for Cu²⁺ over other transition metal ions. Mn²⁺, Co²⁺, Ni²⁺, Cd²⁺, and Zn²⁺ ions were separated from Cu²⁺ using HNO₃ eluent with the cyclenbowl column. The preconcentration of Cu²⁺ in parts per billion level from a high concentration matrix of Mn²⁺, Co²⁺, Ni²⁺, Cd²⁺, and Zn²⁺ ions was achieved in the cyclenbowl column using a nitric acid eluent gradient. Recovery of Cu²⁺ at >98% was obtained based on direct interaction of metal ion and cyclen. Although Mn²⁺, Co²⁺, Ni²⁺, Cd²⁺, and Zn²⁺ were not separated by HNO₃ eluent, addition of oxalic acid yielded a very good separation. A retention mechanism is proposed for the latter system in which the protonated cyclen units attract negatively charged HC₂O₄⁻ ions that cooperate with cyclen sites in retaining transition metal ions.

Topics: Calixarenes; Cations; Chromatography, Liquid; Cyclams; Heterocyclic Compounds; Phenylalanine

N-undecyl cyclen and a resorcinarene bowl bearing four cyclen arms have been applied as anion exchangers in ion chromatography by strong adsorption to a reversed-phase column. The column loaded with the resorcinarene bowl cyclen tetramer exhibited significantly better performance in anion separation than that with N-undecyl cyclen monomer in isocratic elution mode. Both columns were tested for polarizable anion preconcentration or removal. By changing the eluent type from sodium bicarbonate to sodium hydroxide, the degree of protonation of the cyclen molecules could be modified, and the column capacity for anion retention adjusted thereby. Capacity gradient elution was successfully applied to removing sample matrix ions in the preconcentration of perchlorate and perrhenate ions as example analytes.

Topics: Anions; Calixarenes; Chromatography, Liquid; Cyclams; Environmental Pollutants; Heterocyclic Compounds; Perchlorates; Phenylalanine; Sodium Pertechnetate Tc 99m