STUDIES ON THE CHARACTERISTICS OF SOME ION-SELECTIVE ELECTRODES WITH AC IMPEDANCE METHODE

The impedance plane plots for four ISEs, two liquid membrane bile salt ISEs and two PVC membrane Ca ISEs based on ETH 1001 and phosphate, were measured from 65 kHz to 0.01\Hz. All the impedance spectra obtained showed two semicircle and a Warburg impedance (Fig.1). The bulk resistance of membrane, R-b, and the charge-transfer resistance, R-ct, were estimated from the high frequency and the low frequency semicircles respectively. The activation energy for ion transport in membrane, E-2, and the apparent standard exchange current density, I-0, were calculated from the R-b varied with temperature and the R-d varied with the ion concentration in batching solution respectively. The E-b values for two PVC membrane ISEs are similar though the R-b values are not, and the E-a values and R-b values for two liquid membrane ISEs are also the case, The E-b values for the former are three times larger than the later. This results means that the ion transport in PVC membrane is more difficult than in liquid membrane. The ETH 1001-based Ca ISE is a very good Nernstain sensor. The I-0 values of it bathing in Ca2+ solution is 1.9 x 10(-4) A.cm(-2). The potentiometric responses of the two liquid membrane ISEs are near Nernstain. The I-0 of them bathing in the potential-determining ion solution are in 1 x 10(-8) -6 x 10(-3) A.cm(-2) range. The Warburg impedance was eliminated by the strong anion surfactant added in bathing solution. It was shown that the diffusion of the potential-determining ion near the membrane/solution interface is inhibited, then the potentialmetric response for the potential-determining ion is disturbed.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000207572700012&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, PhysicalSCI(E)中国科学引文数据库(CSCD)02190-195