Abstract: Dicarboxylic acid diamides having the formula I ##STR1## 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.

Abstract: Plastic material compositions which comprise a plastic material matrix containing a benzhydrol-tetracarboxylic acid tetraester as a plasticizer are disclosed. The plasticizer is firmly anchored within the matrix such that migration of the plasticizer, and any other optionally present matrix components having a molecular weight of at least 100, are inhibited within the matrix. The plasticizer and matrix components are inhibited from eluting from the matrix when the matrix is brought in intimate contact with a liquid or solid material. These compositions are particularly useful as shaped bodies possessing highly elastic and adhesive characteristics.