Journal of Chromatography B, 990 (2015) 198–202 Contents lists available at ScienceDirect Journal of Chromatography B jou rn al hom epage: www.elsevier.com/locate/chromb Comparison of retention properties of stationary phases imitated cell membrane in RP HPLC Szymon Bocian ∗ , Bogusław Buszewski Department of Environmental Chemistry & Bioanalytics, Faculty of Chemistry, Nicolaus Copernicus University, Gagarin 7 St., 87-100 Torun, Poland a r t i c l e i n f o Article history: Received 1 December 2014 Accepted 31 March 2015 Available online 7 April 2015 Keywords: Liquid chromatography Retention mechanism Mimics of cell membrane a b s t r a c t Chromatographic properties of two columns was compared: commercial IAM.PC.DD2 that imitates the cell membrane and home-made Amino-P-C18 (N,O-dialkylphosphoramidate C18). The comparison has been done by correlation of retention (log k w parameters) of a series of solutes: hydrophobic (alkyl ben- zene derivatives and PAHs) and polar, with both acidic (flavonoids) and basic (nucleosides and nucleic bases) character. The slope of correlation plots for hydrophobic compounds and polar basic was very close to 1.0 that confirms the chromatographic similarity. Only for flavonoids the slope of correlation plot was 1.5. For hydrophobic compound retention parameters log k w were also correlated with hydrophobic parameter log P with very good determination coefficients. © 2015 Elsevier B.V. All rights reserved. 1. Introduction To obtain the pharmacological and therapeutic effects of drug, a drug has to cross various cellular barriers. It may be done by pas- sive diffusion and/or by carrier-mediated uptake. From this point of view, drug design and discovery cannot have pharmacodynamic potency as the sole criterion of optimization. The pharmacokinetic behavior should be considered too, especially absorption and dis- tribution of a given substance [1]. Numerous quantitative structure–permeability relationship (QSPR) studies have demonstrated that lipophilicity is a key param- eter in predicting and interpreting the drug permeability [2–5]. In that case, the lipophilicity is related to membrane partition- ing and hence passive transcellular diffusion. Within QSPR studies, lipophilicity is often equated with the n-octanol/water parti- tion coefficient (log P). The partitioning in this solvent system is traditionally accepted as an informative model of membrane par- titioning [3,6]. An alternative approach for measuring partition coefficients is based on artificial membranes, i.e., liposomes [7], micelles [8], and using immobilized artificial membrane in liquid chromatography [1,9–11]. Immobilized artificial membrane (IAMs) stationary phase is pre- pared by covalent binding of a monolayer of phospholipids to silica surfaces [12], thus it mimics the lipid bilayer of a cell membrane ∗ Corresponding author. Tel.: +48 56 611 43 08; fax: +48 56 611 48 37. E-mail address: bocian@chem.umk.pl (S. Bocian). on a solid matrix. The prototype IAM stationary phase as well as the currently commercially available IAM materials are made by linking diacylphosphatidylcholine (PC) molecules covalently to silica-propylamine through their ω-carboxylic group on the C2 fatty acid chain. A simple method to measure the partition of a solute between phospholipids and an aqueous phase is the HPLC determination of its chromatographic capacity factor, k  , using IAM stationary phase were introduced by Kaliszan and co-workers [13]. The chro- matographic capacity factor, k  , is linearly related to equilibrium partition coefficient (K) of a solute that partitions between a stationary phase and a mobile phase [13,14], by the following equa- tion: k  = V S V m K (1) where V m is the total volume of solvent inside chromatographic column and V s is the volume of the IAM bonded phase. The values of capacity factor determined in 100% aqueous mobile phase (k IAM w ) are direct measures of the partition of solutes between phospholipids and water. If solutes require the addition of an organic modifier into the mobile phase, to obtain satisfied retention, parameter k IAM w , can be easily calculated by performing an extrapolation to pure water in the mobile phase. During last two years a novel stationary phases were introduced into the liquid chromatography: N,O-dialakylphosporamidate- based materials [15,16]. These stationary phase exhibits similar properties to IAM stationary phase due to similarities in the functional groups present in their structures, except the polar phosphatidylcholine “head groups”. Both materials possess in their http://dx.doi.org/10.1016/j.jchromb.2015.03.033 1570-0232/© 2015 Elsevier B.V. All rights reserved.