ION-SELECTIVE ELECTRODES BASED ON NEUTRAL CARRIERS AS SENSORS FOR ORGANIC CATIONS - OCTYLAMMONIUM-SELECTIVE MEMBRANE ELECTRODES BASED ON PODANDS CONTAINING PHOSPHORYL GROUPSстатья
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Аннотация:Plasticized membranes containing neutral carriers (usually crown ethers) are increasingly widely used for the potentiometric determination of amines. Such electrodes are distinguished by their high selectivity and satisfactory operating characteristics [1, 2]. A basic step in their operating mechanisms is the formation of a ''host-guest'' complex: the protonated amine cation bonds to the carrier via hydrogen bonds and ion-dipole interactions [3]. It may be predicted that macrocyclic polyethers could be replaced by open chain ionophores, in particular by podands in which basic terminal groups (e.g., phosphine oxide) are added to a polyether chain (CH2CH2O)n. Such reagents interact with metals as the crown ethers do [4, 5] and with amines to judge from fragmentary reports [6]. Procedures for the synthesis of podands are simpler than for cyclic polyethers which facilitates structural variation to obtain the most effective ionophores. Because of the relative conformational lability of the noncyclic molecules electrodes based on them are likely to have excellent kinetic characteristics. Podands with diphenylphosphine oxide terminal groups and polyether chains of different lengths (I-V) have been synthesized and tested as electrode-active substances in this work. For comparison, the properties of triphenylphosphine oxide, the analogue of the ''isolated terminal group'' and the classic crown ether, dibenzo-18-crown-6, have been investigated. [GRAPHICS]