Chang Suk Kim

Syntheses and separating properties of triazacrown and AM18C6 bonded Merrifield peptide resins

Abstract Separation of lithium and magnesium isotopes by cation exchange elution chromatography was carried out with a synthesized 1,13,16-trioxa-4,7,10-triazacyclooctadecane (N3O3)-4,7,10-trimerrifield peptide resin and with a 2′-aminomethyl-18-crown-6 (AM18C6) bonded Merrifield peptide resin. The resins have a capacity of 0.1 and 2.3 meq/g dry resin. A single stage separation factor of lithium isotopes, 1.018 was obtained by the Glueckauf theory from the elution curve and isotopic assays. The heavier isotope, 7Li was concentrated in the resin phase, while the lighter isotope, 6Li concentrated in the solution phase. On the other hand, the heavier isotopes of magnesium were concentrated in the solution phase, while the lighter isotopes were concentrated in the resin phase. The separation factors of 24Mg–25Mg, 24Mg–26Mg, and 25Mg–26Mg isotope pair fractionations were 1.012, 1.022, and 1.012, respectively.

Magnesium isotope effect in the aqueous-monoazacrown bonded merrifield peptide resin

Separation of magnesium isotopes was investigated by chemical ion exchange with synthesized 1-aza-15-crown-5 bonded Merrifield peptide resin using elution chromatography. The capacity of novel monoazacrown ion exchanger was 2.3 meq g−1 dry resin. The heavier isotopes of magnesium are concentrated in the resin phase, while the lighter isotopes are enriched in the solution phase. The glass ion-exchange column used in our experiment was 35-cm long with an inner diameter of 0.2 cm, and 2.0 M NH4Cl solution was used as an eluent. The single-stage separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays. The separation factors of 24Mg2+–25Mg2+, 24Mg2+–26Mg2+, and 25Mg2+–26Mg2+ were 1.014, 1.026, and 1.012, respectively.

Formation kinetics of triaza-crown-alkanoic acid complexes of first-row transition metal(II) ions

Abstract The complex formation reactions of divalent metal ions of Co2+, Ni2+, Cu2+ and Zn2+ with the macrocyclic ligands 1,7-dioxa-4,10,13-triazacyclopentadecane-4,10,13-triacetic acid, 1, and 1,7-dioxa-4,10,13-triazacyclopentadecane-4,10,13-tripropionic acid, 2, have been studied by using stopped-flow and conventional spectrophotometry. The measurements were made at 25.0 ± 0.1°C in an aqueous solution of 0.1M (NaClO4) ionic strength. The formation reaction takes place by rapid formation of an intermediate complex (MH2L+∗) in which the metal ion is incompletely coordinated. This may then proceed to the final product in the rate-determining step. The stability constants (logK MH2L +∗) and the second-order rate constants (kOH ) for the rearrangement of the intermediate complex have been determined from the kinetic data. In the pH range examined, the monoprotonated (HL2−) form of ligands 1 and 2 is the kinetically active species despite of their low concentration. The structure of the intermediate is propos...

Synthesis of AM15C5 bonded Merrifield peptide resin and its separating properties

Abstract A 2-aminomethyl-15-crown-5 (AM15C5) bonded Merrifield peptide resin was synthesized. The capacity of this crown ion exchanger was 2.25 meq/g of dry resin. The heavier isotopes of magnesium were enriched in the solution phase, while the lighter isotopes were enriched in the resin phase. The hydration and isotope mass effects dominated over those of the complexation and properties of the exchanger. The separation factors of 24Mg2+/25Mg2+, 24Mg2+/26Mg2+, and 25Mg2+/26Mg2+ isotope pair fractionations were 1.0012, 1.0023, and 1.0011, respectively.