Redox probe-based amperometric sensing for solid-contact ion-selective electrodes

The transformation from the traditional potentiometric response of an ion-selective electrode (ISE) to other signal readout is promising to realize the potential signal amplification. In this work, the redox probes, including ferrocyanide/ferricyanide (Fe(CN)(6)(3-/4-)), hexaammineruthenium (Ru(NH3)(6)(3+)) and ferrocene derivatives, were introduced to read out the potentiometric response for the solid-contact Ca2+-ISE. The mechanism is that the oxidation current of the redox probe on a glassy carbon electrode is modulated by the potential of the ISE through changing the concentrations/activities of Ca2+ under the control of the constant applied potential. Results show that the linear range and the slope sensitivity for detection Ca2+ by using the amperometric signal based on Fe(CN)(6)(4-/3)-redox probe are adjustable through changing the applied potentials. Moreover, the redox probe-based amperometric signal for the solid-contact Ca2+-ISE is found to be related to both of the types of the redox probes and the electrode areas. This work provides a convenient and general method for translating the potential response at mV grade to the amperometric signal at the mu A level, and is promising for detection of ions with high sensitivity by using the ISEs.

Automated summary

The study successfully translated the potentiometric response of solid-contact Ca2+-ISE into adjustable and sensitive amperometric signals by introducing redox probes. This method is convenient and promising for high-sensitivity ion detection using ISEs.