Impedance-Assisted Amperometry and Voltammetry for Biological Applications

Presenter and Advisor Information

Jennifer Schreiber, Illinois Wesleyan University
Melinda Baur, Faculty Advisor, Illinois Wesleyan University

Submission Type

Event

Expected Graduation Date

2013

Location

Atrium, Center for Natural Sciences, Illinois Wesleyan University

Start Date

4-20-2013 2:00 PM

End Date

4-20-2013 3:00 PM

Disciplines

Chemistry

Comments

AC impedance was used at carbon fiber microelectrodes to assist in making electrochemical measurements in biological systems. A high frequency sine wave (100 kHz, 20 mV rms) was added to the potential applied for amperometry or voltammetry, and the amplitude of the resultant AC current was measured with a lock-in amplifier. This amplitude is inversely proportional to the solution impedance close to the carbon fiber electrode. The AC signal can be recorded simultaneously with the faradaic current, and requires no electrode modifications. We have found that such measurements are invaluable for reproducibly positioning the electrode close to single cells and close to the surfaces of isolated tissues. The AC signal is also useful for confirming that stimulant solution ejected from a micropipette reaches the electrode vicinity. Furthermore, we have detected small changes in ionic strength during exocytosis that are independent of the redox reactions occurring at the surface of the electrode. Minimal hardware, consisting of only a modified pre-amplifier and a lock- in amplifier, is required to add this capability to conventional electrochemical instrumentation.