Bipolar Pulse Conductance Measurements With Ion-Selective Electrodes

A novel conductometric approach to monitoring of the calcium and fluoride ion-selective electrodes (ISEs) is presented as an alternative to the classical potentiometric technique. Bipolar pulse conductometric monitoring of ISEs does not require a real reference electrode; two voltage pulses of equal time duration, equal magnitude, but opposite polarity are applied to a metal (inert) electrode, and the resulting current through the ISE is measured at the end of the second pulse. The performance of the calcium electrode under potentiometric and conductometric monitoring is similar in most respects; the conductometric method simply short-circuits the ISE potential and allows it to generate a current that is measured along with the current induced by the voltage pulse. Therefore, working curve detection limits, linear ranges, and general shapes are quite similar, as is the selectivity of the electrode to calcium in the presence of a variety of interfering species. The measured current is proportional to log (calcium concentration) rather than log (calcium activity), and it is shown that voltage pulses greater than 15 mV in amplitude are responsible for the concentration dependence. Also voltage pulses force the ISE to respond to abrupt changes in Ca('2+) concentration more rapidly than it does in the potentiometric mode.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Powley, Charles Robert

• Chemistry, Analytical

Identifier

(UMI)AAI8218541

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70190