Chronopotentiometry is an electrochemical technique that applies a constant current between electrodes and measures the potential over time. It can be used to investigate electroporation of bilayer lipid membranes. When a constant current is applied, the potential gradually changes as oxidation and reduction reactions occur at the electrodes. Ultimately, the concentration of one species is depleted at the electrode surface, causing a rapid change in potential. Chronopotentiometry provides simple information about membrane pores but is not well-suited for studying capacitive currents.

1. chronopotentiometry
Done by
K. Revathi
I-M.sc Chemistry

2. Introduction…
•Stationary electrode
•Unstirred = mass transport by diffusion
• Constant current applied between electrodes
• Measure potential vs time

3. Introduction
• Chronopotentiometry is useful for investigation of electroporation
phenomenon of bilayer lipid membranes.
• The measurements are provided in current-clamp conditions.
• This technique allows to obtain only simple pore in the membrane.
• The pore has size about few nano meters - size similar to the membrane
thickness.
• The pores are stable or irregular oscillating.

6. Theory of Chronopotentiometry
•A gradual change in E occurs as [Red] goes up and [Ox] goes
down (transition region) Ultimately the surface concentration of
Ox goes to zero & to sustain the constant current applied,
electrode potential makes a rapid change to the value required to
make a new process go

9. Chronopotentiometry Output Wave
E
time
Transition
Time (τ)
At start no Red is present so E is not defined
Point at which Ox
is used up

14. Hardware
•The program controls the KSP measurement system with
following modules:
• DPTG-461 - programmable potentiostat - galvanostat
ADC-1204 – analog – to - digital convereter.
DAC-1201 - digital-to- analog convereter.
TIMER-49 - programmable timer
• Measurements are made in a four-electrode arrangement

15. Features of the program
• saving of data and printing of the report.
• writing of data as a text file for using in worksheets and graphic
programs.
• selection 2-, 3- or 4-electrode system.
• setting up to 10 methods (sets of measurement parameters and
experiment descriptions).
• readout of data directly from the graph.
• readout of curve slope directly from the graph.
• zoom of the graph.

17. Mainwindow of the "Chronopotentiometry" program.
• The curve shows electroporation of the bilayer lipid membrane made from egg yolk lecithin.
• The begin increasing of the potential is for the membrane without pores.
• Membrane voltage increased with speed dependent on current intensity, membrane capacitance and
membrane resistance.
• When voltage attains to the breakdown voltage value the membrane resistance rapidly decreases
causing decreasing of voltage on the membrane.
• Size of the pore irregular oscillates and membrane potential changes.
• There is an irreversible breakdown of the membrane.
• The generated pore is full filled by the electrolyte.
• Disconnecting of the current flowing causes closing of the pore and recovering of uniform structure of
the membrane in time of seconds to minutes.

18. Used files
• CHRONPOT.EXE - main program file
CHRONPOT.INI - configuration file
CHRONPOT.HLP - help file
• DPTG.DLL - driver for the potentiostat/galvanostat module
ADC.DLL - driver for the analog-to-digital converter module
DAC.DLL - driver for the digital-to-analog converter module
TIMER.DLL - driver for the programmable timer module

21. Application of chrono potentiometric measurements
• studies of membrane electroporation phenomenon.
• studies of membrane transport processes.
• studies of basic properties of membranes as capacitance and
resistance.

23. Summary
• In reality it is better done by other methods.
• Chronopotentiometry illustrates constant current
situation in electrochemistry.
• Chronopotentiometry is very poor at handling
capacitive current.

24. Reference
1. S. Kalinowski and Z. Figaszewski, A four-electrode potentiostat-
galvanostat for studies of bilayer lipid membranes, Meas. Sci. Technol., 6 (1995)
1050-1056.
2. S. Kalinowski, G. Ibron, K. Bryl and Z. Figaszewski, Chrono potentiometric
studies of electroporation of bilayer lipid membranes, Biochim. Biophys. Acta, in
press (1998).

25. Thank you friends..