Abstract: The present invention relates to ?-conjugated fluoroionophores, methods for their preparation, and their use and a method for determining an alkali ion. Fluoroionophoric compounds of the general formula I are described Ionophore-?-Linker-Fluorophore??(I) wherein the Ionophore is an anilino containing crown ether or cryptand with one or more anilino donor moieties as electron donors, forming a stable complex with an alkali metal ion the ?-Linker is an aromatic or heteroaromatic conjugative linking moiety, and the Fluorophore is an electron acceptor moiety. Variation of the ionophoric unit offers a broad spectrum of detectable K+ and Na+-concentrations, ranging from high concentration around 800 mM down to very low concentrations around 3 mM.