Asymmetric flow field-flow fractionation of liposomes: optimization of fractionation variables

The purpose of this study was to investigate the influence of ionic strength of the carrier liquid, cross flow rate, focus flow rate, and sample load on the retention behavior of liposomes in asymmetric flow field-flow fractionation (AF4). Two differently prepared samples of large unilamellar vesicles (LUV) were used. Experiments were performed varying the factors systematically and evaluating their effect on both retention behavior of the liposomes and on particle size as obtained from online coupled multi-angle light scattering (MALS) analysis. The results showed that the focus flow rate had the least influence on the elution of liposomes. Elution of LUV is mainly governed by the chosen cross flow condition and ionic strength of the carrier liquid as well as its sample load. Optimal fractionation and size analysis were achieved using a sample load of about 10 microg, a cross flow gradient from 1.0 to 0.1 mL/min over 35 min and a carrier solution of NaNO(3) with a concentration of 10 mM.