| abstract |
Dicarboxylic acid diamides having the formula I <IMAGE> I wherein the radicals R are selected from hydrogen, alkyl, alkenyl and alkynyl with up to 20 carbon atoms, have a high selectivity for lithium ions over other alkali metal ions and alkaline earth metal ions. Ion selective membranes and ion selective coatings as well as ion selective test devices, like e.g. test strips, which contain said compounds of formula I as ion selective component, can be used for the determination of lithium ions in liquid media. Said membranes and test devices are also suited for the determination of the concentration of lithium ions in biological fluids in which low concentrations of lithium ions and high concentrations of sodium ions are present, like the corresponding determination in blood serum or whole blood. The ion selective membranes have a period of life of several months even if they are frequently contacted with blood serum or blood. Lithium complexes of the dicarboxylic acid diamides of formula I were prepared in crystalline form and the new carboxylic acid diamides of formula I were prepared by etherifying the corresponding diols. |