Retention artificial membrane columns

Determination of the Retention Time on Artificial Membrane Columns... 

M., La Rotonda, M. L, Testa, B. Structural properties governing retention mechanisms on immobilized artificial membrane (lAM) HPLC columns. Helv. Chim. Acta 2002, 85, 519-532. 

Correlation to HAS and IAM column retentivity VD is a function of albumin binding and partitioning into phospholipid membranes, and these can be measured using affinity HPLC columns Retentivity on human albumin and immobilized artificial membrane HPLC columns [33]... 

Due to their better biomimetic properties, phospholipids have been proposed as an alternative to 1-octanol for lipophiiicity studies. The use of immobilized artificial membranes (lAM) in lipophiiicity determination was recently reviewed and we thus only briefly summarize the main conclusions [108]. lAM phases are silica-based columns with phospholipids bounded covalently. lAM are based on phosphatidylcholine (PC) linked to a silica propylamine surface. Most lipophiiicity studies with lAM were carried out using an aqueous mobile phase with pH values from 7.0 to 7.4 (log D measurements). Therefore, tested compounds were neutral, totally or partially ionized in these conditions. It was shown that the lipophiiicity parameters obtained on I AM stationary phases and the partition coefficients in 1-octanol/water system were governed by different balance of intermolecular interactions [109]. Therefore the relationships between log kiAM and log Poet varied with the class of compounds studied [110]. However, it was shown that, for neutral compounds with log Poet > 1, a correspondence existed between the two parameters when double-chain lAM phases (i.e., lAM.PC.MG and IAM.PC.DD2) were used [111]. In contrast, in the case of ionized compounds, retention on lAM columns and partitioning in 1 -octanol / water system were significantly different due to ionic interactions expressed in lAM retention but not in 1-octanol/water system and due to acidic and basic compounds behaving differently in these two systems. 

Several studies have been undertaken to measure the retention times of compounds on chromatography columns comprising immobilized liposomes or artificial membranes. Liposomes comprise aqueous compartments surrounded by lipid bilayers, whereas the artificial membranes comprise monolayers of phospholipids (Lundahl and Beigi, 1997). Interaction between the compound and the phospholipids present mimics the interaction of compounds with cell membranes. Retention... 

A drug is absorbed through diffusion across a series of separate barriers where the single layer of epithelial cells is the most significant barrier to absorption. Many in vitro methods have been developed for the study of this phenomenon. These methods include small animal gut studies, cell culture (i.e., Caco-2 cell culture model), octanol-water partition coefficients, measures of hydrogen bonding and desolvation energies, immobilized artificial membranes, and retention time on reversed-phase HPLC columns. 

The chemical structure of one of the more popular bonded phases that are used for this purpose is shown in Figure 9.5. Retention factors obtained from simple hydrophobic-bonded phases, like typical C-18 HPLC columns, are not predictive of absorption, but the immobilized artificial membrane (lAM) method has been shown to correlate well with other models and with in vivo absorption data. For example, one study found that it gave a correlation coefficient of 0.858 (taking into account MW) when plotted against rat s intestinal absorption data, for a set of 12 compounds. ... 

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