Electrochemical reference electrodes on a budget - Page 1
Forum section: electronics / projects

author: ChristofferB
author_rank: Frequent Contributor
timestamp: November 10, 2019, 01:55:01 pm
content: Hey all!I've been messing around with making silver/silver chloride reference electrodes for a few days, as preample to a larger project of making a sweepable 3-electrode potentiostat for cyclic voltammetry analyses.And today I've finally gotten them working!See attached diagram for the general idea. The electrode body was made by cutting little discs of approx 1mm thick clay sheet and then letting them dry, and firing them in a gas flame (a few of them popped apart but some survived - use eye protection!!), then epoxying to the end of a 15cm lenght of 7mm glass tubing.The silver electrode was made by coating a lenght of 1mm dia. 99.9% silver wire in silver chloride, this is best done by electrolysis, but the easiest option, and the one i used was to just put a lenght of the wire (bottom 5ish cm) in household hypochlorite bleach for an hour. a grey/blue coating is observed.The wire was mounted in teh tube with some layers of wire insulation and bicycle valve latex tubing, whether the wire is centeredor leans against the edge of the tube doesn't seem to make any difference.The tube is filled to ~3cm with concentrated potassium chloride solution and the wire inserted. When placed in sodium chloride solution, and tested against a similar electrode (I made two), there's only 2-3 mv between them. When measured against a copper foil electrode (reference positive they both measure 220 mv +-10mv.I'm happy with this performance, although I do fear that iron oxide in the clay frit might give some strange signals in analytical voltammetry.Anyway it was an interesting build!--Chris

author: vindoline
author_rank: Unknown
timestamp: November 10, 2019, 03:38:25 pm
content: Once again, very creative Chris! How did you settle on clay? I would have thought a small piece of glass frit would be best. I’m looking forward to seeing what you do with this!

author: SeanB
author_rank: Super Contributor
timestamp: November 10, 2019, 04:37:27 pm
content: Very nice, and easy to refill as well. Now all you need to do is figure out how to blow soluble glass electrodes. Wonder if you could use some sintered silica instead of the clay, as it would be very easy to bond it to the glass without too much loss of porosity.As you work in a lab try to get some broken Hirschmann dispensers, preferably the smaller volume ones, and use the sintered ceramic plunger as an enclosure. I call those my 200 Euro knife dressers.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: November 10, 2019, 06:09:47 pm
content: Thanks!The clay frit idea came from a lot of early electrochemical cells, a lot of which used clay pots to separate the electrolytes.Certainly a lot of materials, glass frit, or the vycor frits used on commercial electrodes would be better. I am trying to draw the general trend in my scientific products that if a scientific specific/lab specific component can be substituted with a commercial/everyday component without significant incident, I'l use the more accesible part.I was considering using cellophane as well. It has less contaminating ions, and is also (some of it) semipermeable.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 10, 2019, 07:00:47 pm
content: Very interesting !I just started using my Keithley 2450 for 3-electrode potentiostat and cyclic voltametry analyses.It is a very special field.What are you planning to do with the cyclic voltametry analysis?

author: ChristofferB
author_rank: Frequent Contributor
timestamp: November 10, 2019, 11:53:08 pm
content: Nice! I've read some articles replacing older electrochemical gear with SMU's as well.I don't have any specific need for this instrument right now, it's mainly just to try it out. My research group is however working on a lot of very redox active aromatic macromolecules, so maybe i'll try and sneak the home-built instrument into my thesis. Would certainly add style points i'd think.--Chris