Separation and Purification Technology 28 (2002) 25 – 28 Effect of temperature on separation of purine and pyrimidine bases on novel chelating resin Ahmet Ayar a, *, Bedrettin Mercimek a , Hu ¨ seyin Kara b , Yunus C ¸ engelog ˘lu b a Department of Chemistry, Faculty of Arts and Sciences, Uniersity of Nig ˘de, 51200, Nig ˘de, Turkey b Department of Chemistry, Faculty of Arts and Sciences, Uniersity of Selc ¸uk, Konya, Turkey Accepted 18 January 2002 Abstract The novel chelating resin poly-bis [4-(4-biphenyl)oxamidine]-diaminoglyoxime (PLH 2 ) has been modified as ligand-exchange material with Co(II). The possibility of using PLH 2 as ligand exchanger in the chromatographic separation of nucleic acid bases and nucleosides has been studied at various temperatures. PLH 2 offers the advantage of combining high sorption capacity with high selectivity for the ligands. It has a strong driving force for ligand sorption. Ligand-exchange chromatography on Co(II)-loaded functionalized PLH 2 can be a useful alternative method for separation of nucleic acid bases and nucleosides. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Ligand-exchange chromatography; Nucleic acid bases; Nucleosides; PLH 2 www.elsevier.com/locate/seppur 1. Introduction Ligand-exchange is a process first described by Helfferich, and evaluated from the fundamental works of Walton and Stokes [1,2]. The principle upon which ligand-exchange chromatography is based is that a transition metal is fixed on a solid support and this solid sorbent can be used for the exchange of bound ligands of the metal. By using ligand exchange chromatography, lig- ands such as amino acids, amines, purine and pyrimidine bases can be removed from their medium by the formation of complexes with the metal attached to the solid support and conse- quently water or liquid coordinates of the metal will be displaced [3,4]. Nucleic acid bases and nucleosides that possess pairs of free electrons are capable of displaying electron-donating properties and of functioning as ligands as the process can be used to separate mixtures of these components. Another application of ligand-exchange chro- matography is the resolution of optical isomers on chiral bonded phases loaded with a transition metal [5]. Ligand exchange chromatography is a process in which complex forming ligands compounds are separated through the ligands formation and breaking of labile coordinate bonds to a central metal atom on the stationary phase as a partition between the mobile and the stationary phase. The ligands taken up from the external solution or gas * Corresponding author. E-mail address: ahmetayar@nigde.edu.tr (A. Ayar). 1383-5866/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S1383-5866(02)00005-9