title: How to assess the limits of ion-selective electrodes: method for the determination of the ultimate span, response range, and selectivity coefficients of neutral carrier-based cation selective electrodes.
abstract: The span and range of an ion-selective electrode (ISE) has been identified by IUPAC as a potential or activity difference between the upper and lower detection limits of the electrode. Once the span is known, the ultimately attainable detection limit of the ISE can be calculated using its theoretical response slope. In this paper, we propose an original method for the determination of the ultimate span and response range of ISEs. The simple measurement of span is recommended to aid the fast screening of novel ionophores and help to focus optimization processes to the most promising candidates. The measurement of span is combined with a generally applicable procedure for the determination of the three seminal parameters of ISEs: the response slope, the ultimate selectivity coefficients, and detection limit. In the proposed procedure, following the span measurement, two subsequent exponential dilution experiments are completed in which the responses of the electrode for the primary and the interfering ions are tested using a solution of a discriminated ion and deionized water as diluting electrolytes in consecution. The advantages and the practical usefulness of the proposed methods and procedures are demonstrated through the evaluation of the performance characteristics of novel and well-characterized ionophore-based potassium and calcium sensors.
authors.affiliation: Research Group for Technical Analytical Chemistry of the Hungarian Academy of Sciences, Budapest University of Technology and Economics, Hungary.
authors.forename: Róbert
authors.initials: R
authors.lastname: Bereczki
authors.forename: Boglárka
authors.initials: B
authors.lastname: Takács
authors.forename: Jan
authors.initials: J
authors.lastname: Langmaier
authors.forename: Matthew
authors.initials: M
authors.lastname: Neely
authors.forename: Róbert E
authors.initials: RE
authors.lastname: Gyurcsányi
authors.forename: Klára
authors.initials: K
authors.lastname: Tóth
authors.forename: Géza
authors.initials: G
authors.lastname: Nagy
authors.forename: Erno
authors.initials: E
authors.lastname: Lindner
mesh_terms: D002118:Calcium / Q000737:chemistry*; D017736:Ion-Selective Electrodes; D008567:Membranes, Artificial; D015394:Molecular Structure; D011188:Potassium / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D008567:Membranes, Artificial; D011188:Potassium; D002118:Calcium