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indium electrodes

Udin, Susan SUdin at ubmedb.buffalo.edu
Wed Jun 28 21:15:31 EST 1995


I don't use indium electrodes, but I do use woods metal electrodes 
(Dowben-Rose) with gold 
and platinum plating, so I may be able to help you.  I plate across 5 
megohms.  For the gold, I use Dalic alkaline gold plating solution (with 
cyanide), code 3020, that I get from SIFCO in Cleveland, OH.  It's expensive, 
but it lasts forever.  I'm on my third bottle in 25 years.  I plate for about 
6 seconds until I get a nice round ball of a few microns in diameter.  If 
the ball isn't rount, pull it off and start again.  

For platinum, I make up my own solution.  Here's the recipe:
    A: 1 g H2PtCl6/6H20 (hexachloroplatinic acid, hexahydrate, FW 517.92)
        100 ml H20
        0.5 mg lead citrate
    B. 25 mg agarose 
        100 ml H20
        Heat to about 70o to dissolve
        Add Solution A and top off with water to 250 ml.

I plate for about 10 sec with platinum.  You won't see much difference in 
size compared to the gold ball.

My application is recording from axon arbors in the optic tectum of the 
frog.  These electrodes also can be used for recording from cells.  

Good electrodes generally have a resistance of about 100 K at 1000 Hz.  I 
don't bother to test them that way, though.  I just try them out in the 
brain.  A good electrode will cause the noise level to go down about 50% when 
you first touch the brain.

Good luck,

Susan Udin
Dept. of Physiology
Buffalo, NY 14214
sudin at ubmedb.buffalo.edu
REPLY FROM: Udin, Susan
Return-Path: <BIOSCI-REQUEST at net.bio.net>
To: neuroscience at net.bio.net
From: PET101 at ukcc.uky.edu
Subject: indium electrodes
Date: Thu, 22 Jun 95 18:14:55 EDT
Message-ID: <173C51009FS86.PET101 at ukcc.uky.edu>
NNTP-Posting-Host: ukcc.uky.edu
I've been making indium electrodes for extracellular recording, but I'm having
trouble with the plating...What is a good resistance to use to get a nice,
coating when plating the indium with gold and then platinum black?  How long
does it usually take to get a good plating of both the gold and platinum?
Jamie Tittle
pet101 at ukcc.uky.edu

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