High Performance Liquid Chromatography of Structural Isomers Using a Cyclodextrin-Poly(allylamine) Coated Silica Column G. Crini 1 / G. Torri 2 / Y. Lekchiri 3 / B. Martel 1 / L. Janus 1 / M. Morcellet 1. 1Laboratoire de Chimie Macromoldculaire, U.R.A. 351 CNRS, Universit6 des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France 2Istituto Scientifico di Chimica e Biochimica "G. Ronzoni", Via G. Colombo, 81, 20133 Milano, Italy 3Laboratoire de Biochimie, D6partement de Biologie, Facult6 des Sciences, Universit6 Mohamed 1er, Oujda, 60000, Maroc Key Words Liquid chromatography 13-cyclodextrin bonded phase Polymeric stationary phase Phenolic compounds Isocratic elution Summary High performance liquid chromatography (HPLC) sep- aration of substituted phenols by isocratic elution was investigated using a 13-cyclodextrin-bonded column. The HPLC support was prepared in-house. This support was based on silica beads coated with a 13-cyclodextrin- containing poly(allylamine). The retention behavior of some substituted phenol isomers and aromatic com- pounds was studied. The contribution of the amino groups of the polyamine and of the 13-cyclodextrin cav- ity to the separation process is discussed. Two retention mechanisms, inclusion complex formation and acidbase interaction, were found. The effect of the composition and pH of the mobile phase on the separation was also examined. Introduction Environmental aspects of substituted phenols have be- come increasingly important in recent years [1-3]. These compounds are products of many industrial processes and they are common water pollutants. Among a variety of separation methods, chromato- graphic techniques are most commonly used because they can offer not only analytical information but also a separation of compounds within a limited analysis time. These methods include gas chromatography [4], thin layer chromatography [5], and liquid chromatography [5-9]. In this work, we used the property of 13-cyclodextrin (13" CD) to form inclusion complexes with various molecules, especially aromatics. 13-CD is a torus-shaped cyclic oligosaccharide, made up of seven et-l,4 linked D- glucopyranose units. The inside of the cavity is hydro- phobic. This structure gives rise to a remarkable ability to form inclusion compounds with phenolic derivatives. The ability to form inclusion complexes depends on the size and polarity of the host molecule and its shape [10]. The selective inclusion properties of 13-CD can be ap- plied in two ways in HPLC. First, I~-CD can be used as a selective component of the mobile phase in a reversed- phase system [8, 11-13]. Secondly, 13-CD bonded to sil- ica gel in various ways can be employed [9, 14-17]. These two procedures have been used to separate struc- tural isomers of phenolic compounds and aromatic acids. The present paper reports the HPLC separation of sub- stituted phenols by isocratic elution using UV detection. We have prepared a new stationary phase for HPLC, based on silica beads coated with a 13-CD-containing poly(allylamine), which will allow the elution of solutes in the reverse order of their affinity for ~3-CD. This modified polyamine has already been used for the catalysed hydrolysis of aromatic esters in aqueous solu- tions [18]. Another 13-CD polyamine, poly(ethyl- eneimine) (PEI) has been used for chromatographic applications [19, 20] but this is, in fact, a mixture of linear and branched polymers containing both second- ary and primary amino groups. On the contrary, 13-CD poly(allylamine) (PAA) contains only primary amino groups, more accessible than in PEI. Thus it is expected that the grafting of 13-CD onto PAA would lead to well defined derivatives with higher degrees of substitution in 13-CD. 424 Chromatographia Vol. 41, No. 7/8, October 1995 Original 0009-5893/95/10 0424-07 $ 03.00/0 9 1995 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH