Simple, single step potential difference measurement for the determination of the ultimate detection limit of ion selective electrodes


A single step measurement is proposed for evaluating the ultimate detection limit of ion selective electrodes. The essence of the method is the calculation of the detection limit from a potential difference measured across a membrane in equilibrium with deionized water when it is challenged with a relatively concentrated primary or interfering ion solution on one of its sides. It is aimed for fast screening of novel ionophore candidates and for reexamining existing ones to sort out those which are adequate for selective, subnanomolar analysis. The feasibility and the practical usefulness of the method is demonstrated upon the characterization potassium ion-selective electrodes with novel, and well-known ionophores. The proposed potential difference-based method is coupled to subsequent exponential dilutions for the determination the response slopes, selectivity coefficients and detection limits of the tested electrodes. This combination of electrode testing protocols provides full characterization of the studied electrodes and a back to back comparison of the indirectly calculated and directly measured detection limits. The calibration of the electrodes in dilute solutions revealed the superior dynamic response properties of the electrodes with the covalently anchored ionophore in submicromolar concentrations. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

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