The attachment of a tetradecyl chain to the ionophore 18-crown-6 leads to a stronger interaction with a supported lipid monolayer. Some C14-18-crown-6 mols. introduced in the aq. phase are incorporated in the phospholipid membrane. This process is used to produce ionophore contg. lipid monolayers of detd. compn. at the surface of an electrode. The ionophore content and the sensitivity to K+ of these layers are detd. by capacitance measurements. [on SciFinder (R)]