Instructions KCl Bridge Electrode Holder

Instructions KCl Bridge Electrode Holder
KCl Bridge Electrode Holder
The KCl Bridge Electrode holder is just like a standard holder with an extra section added in the middle.
This new section links the amplifier input with the section that actually holds the electrode. The middle
section holds a small amount of KCl solution where it can form a circuit with the silver chloride pellet
and the quartz capillary tube.
The front part of the holder features the usual silicone seal for the electrode. The glass electrode is
inserted in this part until it can go no further. Then the securing nut is twisted to form a tight seal. On
patch electrodes this section will feature a port for attachment of a suction tube.
Where the front section of the holder meets the middle section, there is another thread that connects the
two parts. Here a silicone seal is compressed against a black plastic backing plate. At the center of the
seal and the plate is a tiny hole to accommodate the quartz capillary tube. The capillary is pushed
through this hole so that its end is securely seated in the middle compartment of the pipette holder.
Tightening the front section into the middle section compresses the rubber seal on the quartz capillary
and holds it in place.
The quartz capillary is the conduit down into the recording pipette. The capillaries supplied are 100µm
and 200µm ID. Try to use the 200µm capillary if you can since it is better (if your pipette is big
enough), otherwise the 100µm can be used. The 200µm ID capillary should have a 100µm silver wire
(supplied) inserted to lower resistance. The silver wire must be chlorided and should be cut just a little
shorter than the tubing and sit in the tubing so that the wire does not protrude from either end. The
100µm ID tubing is used for patch recording and the 200µm ID tubing is used for whole cell recording.
In either case, the capillary is filled with warm KCl by using the luer-lock compression fitting (supplied)
which must be mounted on a syringe. The quartz capillary is inserted into the compression fitting, the
fitting is tightened, and the KCl is injected into the quartz capillary until small droplet forms at the open
end. (1 molar KCl is recommended.)
Once the capillary is full it can be placed in the holder as described above. The capillary can also be
filled if it is installed in the holder properly, and if the KCl reservoir is filled, by simply applying
pressure to the KCl filling port on the middle section of the pipette holder. Pressure should be applied
until a small droplet forms on the end of the capillary tube. (Remove this droplet before installing your
recording pipette.). Do not insert the quartz capillary into your recording pipette if it is dripping. You
do not want to push KCl into your recording pipette so be careful when tightening fittings on the holder
that might increase pressure and push KCl out. After adjustments, wait until the unit stabilizes before
use. In either filling procedure, if the capillary does not fill, it is most likely clogged and in need of
The middle section of the pipette holder, where the KCl is stored, is filled by removing the red cap and
depositing the KCl with a needle. The section should always be full and the cap should always be in
place when in use. This section should be filled before the quartz capillary is inserted.
It is very important to prevent air bubbles from entering the circuit pathway. This means that
precautions must be taken to keep air bubbles from forming in the quartz capillary tube. The best way to
do that is to fill it with warm KCl. On a daily basis one can open the filling port on the KCl module, and
inject some warm KCl into the quartz capillary from the front end using the luer compression fitting and
a syringe. Close the filling port and the holder is ready for the pipette.
Never open up the back section of the holder unless you need to change the silver chloride pellet.
Replacing this section is tricky since the short silver wire of the pellet must be inserted through the back
of the middle section and then into the connector section where it must pass through another seal. If you
need to disassemble this part for any reason, observe how it is set up as you take it apart. Simply put it
back the same way. The use of forceps is recommended.
Things to note about the use of the KCl bridge electrode holder:
The KCl Bridge electrode holder allows the user to record from cells without the need for
chloride containing solutions in their recording pipette. KCl will be in contact with the recording
solution via the quartz capillary tube. Since the tube has such a small ID, very little KCl will diffuse out
even over several hours. Also, the small ID of the tube creates a wire with an OD of 0.1mm which is
less than ½ the diameter of most silver wires. The noise that a wire adds to a recording is proportional
to the Log of its OD, so a smaller wire will give a quieter recording. In addition, there is no need to fill
the recording pipette all the way to the back. It only needs to be filled up enough to make contact with
the quartz capillary—further lowering noise! After usage, the holder does not have to be emptied, but it
should be stored with the tip of the quartz capillary submerged in KCl so crystals don’t form in the
quartz capillary tube. So say good-by to baseline shift and enjoy the next generation of pipette holder
for electrophysiology!
For reference please see: Snyder, Kriegstein and Sachs, A convenient electrode holder for glass pipettes
to stabilize electrode potentials, Pflugers Arch. 438: 405-411 (1999)
Cleaning the Holder
The holder should be cleaned every few weeks. If excessive noise is seen, then the holder should be
emptied, disassembled, flushed out with distilled water followed by methanol and then dried thoroughly.
Again, do not remove the silver chloride pellet or open this section, unless the pellet or wire needs
Storage for use
When the holder is being used for experiments, and it is filled with KCl with the quartz capillary
installed, it is important not to let the capillary dry out. If the KCl dries out then the capillary will
become clogged and will need to be replaced. The best thing to do is store the holder overnight in a way
that the tip of the KCl filled capillary is submerged in KCl solution. Don’t forget each day to replace the
KCl in the quartz capillary with fresh warm KCl to prevent air bubbles!
KCl Bridge Pipette Holder
Middle section of holder is filled with KCl. Red
vinyl cap seals KCl liquid in holder. To fill with
KCl, remove red cap and inject KCl with
syringe needle until chamber is full, replace cap.
KCl filling port.
When front section is screwed into this section it
compresses the red seal which holds quartz
capillary tube. Capillary must go through seal
into KCl chamber.
Rear section of holder is
used to connect to
amplifier. All major brands
can be accommodated.
Gold pin makes contact
with silver wire from the
Ag/Cl pellet sealed in
middle chamber
Front section of holder is
similar to standard pipette
holders, however it is shorter.
Standard KCl Bridge holder
size is for 1.5mm glass, other
sizes upon request.
Assembly Diagram of KCl Bridge Pipette Holder
KCl pellet
o-ring seal.
Silver wire
o-ring seal.
KCl module.
“Gold” pin for
amplifier connection.
Quartz capillary
compression plate.
module; BNC
or Axon style.
Pipette holder module with
o-ring for glass pipette.
KCl filling port
Securing nut. (Hole may
be ordered from 1.22.0mm. 1.5mm standard.)
Capillary oring seal.
chloride pellet
and silver wire.
For Further information contact:
ALA Scientific Instruments, Inc.
60 Marine Street
Farmingdale, NY 11735
Tel: 631.393.6401
FAX: 631.393.6407
Email: [email protected]
Or contact your local dealer.
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