Abstract: A set (1) comprising at least two ion-selective solid-contact electrodes comprises at least two ion-selective measuring points (6). Each measuring point (6) comprises a metal conductor (3) and/or an inner layer (7) of a conductive polymer and an outer, ion-selective membrane (8). At least two measuring points (6) are selective in each case with respect to a different ion of an analysis solution. One of the solid-contact electrodes can be used as a reference electrode.

Abstract: A new type of ion-selective solvent polymeric or liquid membrane electrode is constructed which allows to extend the measuring range at the lower end by at least six (6) orders of magnitudes. The new method can be used with membranes based on a neutral ionophore, a charged ionophore, or an ion-exchanger. Low detection limits are achieved by maintaining a very low and constant concentration of the primary ion and a sufficiently high concentration of an interfering ion in the internal reference solution. The low and constant concentration of the primary ion is either adjusted with the help of a solution of a hydrophilic ion buffer such as ethylenediamine tetraacetic acid or by adding an excess of a salt of an ion which forms a sparingly soluble salt with the primary ion, such as NaI for the primary ion Ag.sup.+. With the new technique, ion-selective electrodes can be used, for the first time, for environmental monitoring of heavy metal ions such as Pb.sup.2+ and Cd.sup.2+ at the submicromolar level.

Abstract: Keto compounds in which to the carbon atom in the neighboring position to the keto compounds there is bonded at least one strongly electron attracting substituent and/or in which there is conjugating with the carbon-oxygen-double bond of the keto group a .pi.-electron system have the ability of interacting selectively with the anions of oxa acids yielding adducts, chelates or complexes.Provided that in the corresponding keto compounds the keto group is a part of a chromophore, then the shifting of the absorption in the visible range or the ultraviolet range of the wave lengths is observed, compared with the corresponding absorption of the free keto compound.The corresponding keto compounds are used for the determination of the anions of the oxa acids and they e.g. can be the ion sensitive component of a corresponding ions sensitive part for the determination of said anions. Several of said keto compounds can be also used as color indicator for the anions of the oxa acids.

Abstract: New lipide soluble complexes of cations like metal ions and ammonium ions are prepared by reacting an uncharged complex forming substance with the corresponding ions. Preferred uncharged complex forming substances are also new. The new lipide soluble complexes of cations have a wide field of application and those complexes, that is, the complex forming compounds can be used in membranes for the determination of the concentration of cations, like the ion sensitive members of measuring electrodes, or for the performance of an electro dialysis. Metal cations are generally insoluble in organic solvents and due to their solubility in organic solvents the new lipide soluble complexes of cations can be used in many fields of application, e.g. as catalysts for reactions which are performed in organic solvents.