I am planning for preparation of a home-made Ag/AgCl reference electrode. Can anyone suggest how to prepare and calibrate the electrode?
It depends on how accurate you need the potential to be. That paper is probably a good method. I usually do it even more easily since I usually do not care so much about having the exact right potential. I just take a Ag wire and remove any oxide by wiping it or by applying a negative potential sweep. To generate AgCl I put the wire in 10x diluted conc. HCl and apply +1V against my Pt counter electrode (also serving as reference in this case) for 10min. Then I just put this wire into my cell.
I guess many electrochemists laugh at this simple method, but like I said, I think it works good enough as long as you do not care about high accuracy in your potential.
It depends on how accurate you need the potential to be. That paper is probably a good method. I usually do it even more easily since I usually do not care so much about having the exact right potential. I just take a Ag wire and remove any oxide by wiping it or by applying a negative potential sweep. To generate AgCl I put the wire in 10x diluted conc. HCl and apply +1V against my Pt counter electrode (also serving as reference in this case) for 10min. Then I just put this wire into my cell.
I guess many electrochemists laugh at this simple method, but like I said, I think it works good enough as long as you do not care about high accuracy in your potential.
I follow the preparation of Ag/AgCl reference electrode as Andreas Dahin said. We can also prepare by using capillary tubes and frits (e.g. Silica, composites etc). Seal one end of the capillary tube with the frit and fuse it. With the only open end fill (3/4th) it with KCl solution, and then insert the AgCl coated Ag wire inside the capillary.
It is better to replace the KCl soln once in 2 days or everyday which can be easily done by using the syringes.
@Logudurai Replacing the solution is not such a good idea for this reference electrode because for stable potentials you need an equilibrium between AgCl solid and AgCl in solution. This is established by dissolution of the solid.
Dear Dave, I agree with your comment, the process is simple but little tedious for stabilization and replacing the KCl solution. For simple electrolytic solutions, it worked nicely, but for complex biological solutions, it had pbm due to the clogging in the frit. I used to replace the KCl soln by evening before leaving home, and by overnight it will stabilize. Next day morning i calibrate with the commercial reference electrode or any standard solutions.
http://pubs.acs.org/doi/abs/10.1021/ed086p355?prevSearch=shaukatali%2Binamdar&searchHistoryKey=
this paper will provide even more simpler idea ....i used only the sketch pen barrel and its fibrous tip......you can reduce the size and even using this procedure you can prepare Ag/AgCl reference electrode of any dimension..... it will be easiest way to prepare your homemade reference electrode.
The consulrsr site is a goldmine of information, I thoroughly recommend it. In response to Andreas Dahlin, I would have to warn that whether or not you can dangle a silver wire directly in your cell depends on what else you have there. For some electrolytes this is no problem, for others it will contaminate your cell. If you have an oxidising compound present, such as Fe(III) or Cu(II), it will dissolve the Ag to form Ag+ ions and this will ruin your measurements over time.
I've illustrated this problem recently in the linked paper (figure 3), I've also attached the figure to this post. The figure shows that over time Fe(III) in solution reacts with metallic silver to form Ag+ and Fe(II) ions. The arrows indicate the decrease in cathodic current and increase in anodic current as the reaction progresses. This was measured with a silver wire in an RDE cell.
Just be aware that the potential can be off by 0.1 V or so in either direction. We usually measure an open circuit potential of +50 mV against a commercial Ag/AgCl electrode.
To "freshen up" your Ag wire you can put it in 10x diluted HCl, apply -2V (Pt as counter and reference) for 1 min, then rinse and apply +1V for 10 min (in 10x diluted HCl again). This should remove some dirt and oxide on the Ag and regenerate the AgCl layer.
- Badges
- Science topic
- Similar topics
- Chemistry
- Electrochemistry