Research Article Preparation and chromatographic performance of calix[4]crown-5 macrocycle- bonded silica stationary phase A new calix[4]crown-5 macrocycle-bonded silica stationary phase (CL-CIMS) was prepared and applied at the same time to develop a chromatographic procedure to separate aromatic amines, phenols and drugs in this study. The chromatographic behaviors of the prepared stationary phase for these analytes were studied and compared with those of ODS (octadecylsilane). The effect of organic modifier content and pH of the mobile phase on retention and selectivity of these compounds were investigated. Some aromatic amines, phenols or drugs on CL-CIMS were successfully separated. The results show that CL-CIMS exhibits high selectivities for the above analytes in high aqueous mobile phases and a bright prospect in routine, fast separation of aromatic amines, phenols and drug compounds. From chromatographic data, it can be concluded that hydrophobic interac- tion is mainly responsible for the retention behavior as well as hydrogen-bonding inter- action, p–p and dipole–dipole interaction. Keywords: Aromatic amines / Calix[4]crown-5 / Drugs / Silica gel DOI 10.1002/jssc.201000690 1 Introduction The main goal of investigation of high-performance liquid chromatography (HPLC) is searching more efficient station- ary phases and optimization of the separation process. Until now, there exists no universally accepted chromatographic test to choose an appropriate packing material for a particular separation problem [1]. In reversed-phase chro- matography, many descriptors can give certain information to estimate the chromatographic behavior of the stationary phases; i.e. the type of the bonded ligand and its bondage to the surface, the surface coverage, the surface area and the support material that are used to explain the differing properties of the chromatographic materials [2]. Useful changes in selectivity and sample retention can be achieved by selecting appropriate type of stationary phase. There are many contemporary commercially available reversed-phase columns, e.g. RP-C18, RP-C8, RP-phenyl and others. The macrocycle molecule-bonded stationary phases based on supramolecular interaction have been receiving more attention especially due to separation selectivity. Crown ether and cyclodextrin-bonded stationary phases have achieved a great success. For example, Kawaguchi and co-workers [3] prepared the chemically bonded cyclodextrin stationary phases and observed its chromatographic perfor- mance using aromatic compounds. Wu and co-workers [4] reported the preparation and characteristics of a crown ether polysiloxane stationary phase for capillary gas chromato- graphy. Recently, calixarenes also have attracted attention of many researchers because they are able to form reversible complexes with neutral as well as charged molecules [5–8]. The exceptional interest in calixarenes as stationary phases in chromatography results from unique opportunities to influence the specificity and selectivity of these macrocycles [9]. Moreover, the host–guest interactions of calixarenes with solutes are not only determined solely by their hydrophobic cavities, but are also influenced by additional functional groups attached at their rims, which can contri- bute to potential variations in these interactions. Several functionalized calixarenes have been utilized as selectors in LC [10, 11]. Most published reports focus on the applications of one kind of calixarene-bonded stationary phase, and a few papers simultaneously introduced more kinds of calixarene- bonded stationary phases. Calixarene-bonded stationary phases are preferable to the use of calixarene additives because the UV detection of analytes is prevented by strong absorbance of calixarenes. Additionally, poor solubility of most calixarenes precludes their applications as additives in Serkan Erdemir Mustafa Yilmaz Department of Chemistry, Selcuk University, Konya, Turkey Received September 28, 2010 Revised November 26, 2010 Accepted November 26, 2010 Abbreviations: 4-ABP, 4-aminobiphenyl; APS, 3-aminopropyl- bonded silica; CL-CIMS, calix[4]crown-5 macrocycle-bonded silica stationary phase; 4,4-DADPM, 4,4-diaminodi- phenylmethane; NN-DMA, N,N-dimethyl aniline; DPA, diphenylamine; MeCN, acetonitrile; MeOH, methanol; ODS, octadecylsilane; 4-TPMA, 4-triphenylmethyl aniline Correspondence: Professor Mustafa Yilmaz, Department of Chemistry, Selcuk University, 42031 Konya, Turkey E-mail: myilmaz42@yahoo.com Fax: 1903322230106 & 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com J. Sep. Sci. 2011, 34, 393–401 393