Question

Glass microcapillaries are preferred over metallic electrodes because of the former _______

(a) polarizes with input current

(b) does not have sustainable current carrying capacity

(c) has less contact surface area

(d) has sustainable current carrying capacity

This question was posed to me in a job interview.

This intriguing question comes from Microelectrodes in division Bioelectric Signal and Electrodes of Biomedical Instrumentation

Answer 1

Correct choice is (d) has sustainable current carrying capacity

To explain I would say: Metallic electrodes polarize with smaller amplifier input currents. Hence, they tend to develop unstable electrode offset potential and are therefore not preferred for steady state potential measurement. On the other hand, in case of glass micro electrodes have a sustainable current carrying capacity because of the large surface area between the metal and the electrolyte.