Reference Section
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97
Chapter 5
Holder Use
Insertion of Electrode
Make sure the electrode cap is loosened so that pressure on the cone washer is
relieved, but do not remove the cap. Push the back end of the electrode
through the cap and cone washer until it presses against the end of the bore.
Gently tighten the cap so that the electrode is gripped firmly.
To minimize cutting of the cone washer by the sharp back end of the electrode,
you can slightly smooth the edges by rotating the ends of the electrode glass in
a Bunsen burner flame prior to pulling.
Filling Electrodes
Only the taper and a few millimeters of the shaft of the pipette should be filled
with solution. The chlorided tip of the wire should be inserted into this
solution. Avoid wetting the holder since this will increase the noise.
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 bleach for
about 20 minutes, until the wire is uniformly blackened. This provides a
sufficient coat of AgCl to work reliably for several weeks. Drifting or
otherwise unstable offsets during experiments is suggestive of the need for
rechloriding. The chlorided region should be long enough so that the electrode
solution does not come in contact with the bare silver wire.
1
For easy-to-use recipes see Microelectrode Methods for Intracellular Recording and Ionophoresis, by R.D. Purves, London:
Academic Press, 1981, p. 51 or The Axon Guide. Foster City, CA: Axon Instruments, Inc., 1993, p. 83.
