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INSTRUMENT OPERATION
Axopatch 200B, Copyright 1997-1999, Axon Instruments, Inc.
Silver Chloriding
It is up to you to chloride the end of this wire as required. Chloriding procedures
are contained in many electrophysiology texts
1
. Typically the chlorided wire will
need to be replaced or rechlorided every few weeks. A simple, yet effective,
chloriding procedure is to clean the silver wire down to the bare metal using fine
sand paper and immerse the cleaned wire in CHLOROX bleach for about 20
minutes, until the wire is uniformly blackened. This provides a sufficient coat of
AgCl to work reliably for several weeks as an internal reference pipette. Drifting
or otherwise unstable offsets during experiments is suggestive of the need for
rechloriding. The chlorided region should be long enough so that the pipetted
solution does not come in contact with the bare silver wire.
Heat smoothing the back end of the pipette extends the life of the chloride coating
by minimizing the amount of scratch damage. Another way to protect the AgCl
coating is to slip a perforated Teflon tube over the chlorided region.
The chlorided region should be long enough so that the pipette solution does not
come in contact with the bare silver wire.
Replacing the Silver Wire
To replace the silver wire, insert the nonchlorided end through the hole of the
silicone seal and bend the last 1 mm of wire over to an angle of 90°. Press the wire
into the back of the barrel making sure that the silicone seal is flush with the back
of the barrel. Slip the threaded collar over the back of the barrel. With the large
end of the pin directed toward the bent-over wire screw the pin cap down firmly,
but without excessive force. This assures good electrical contact. Screw the pin
cap down firmly but without excessive force.
1
For easy-to-use recipes see Microelectrode Methods for Intracellular Recording and Ionophoresis, by R.D. Purves, London:
Academic Press, 1981, p. 51.
The Axon Guide. Foster City, CA: Axon Instruments, Inc., 1993, p. 83.
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