Some transporters have a high lipophilicity, which results in a poor deliverability. Even when very efficient in anion transport, their activity will appear to be poor when post-inserted from an organic solvent into pre-formed liposomes. To assess the transport activity of lipophilic transporters without bias from their deliverability, they can be pre-incorporated during the formation of the liposomes. This is done in the very first step. A transporter solution is added together with the lipid solutions in the round bottomed flask during the preparation of the lipid film (Section 3.2). For this, the transporters can be added as a solution in chloroform, or in another appropriate organic solvent that is miscible with chloroform and easily evaporated, such as MeOH, MeCN, THF, hexane, or small amounts of acetone, or mixtures of solvents. DMSO and DMF are more difficult to remove from lipid film afterwards but have been used if necessary. The subsequent steps of liposome preparation are to be performed as described in the main procedure. It should be noted that the pre-incorporation of high concentrations (>0.1 mol%) of large or poorly soluble compounds can cause problems in the extrusion step, which can in certain cases limit the maximal concentration of transporter that can be studied via pre-incorporation. After performing experiments using post-insertion and pre-incorporation at identical transporter to lipid ratios, the deliverability of an anionophore can be quantified by dividing the initial rate of transport upon post-insertion by the initial rate obtained by pre-incorporation.