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MI-442 Na+
Ion Microelectrodes
Operating
Instructions |
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Carefully unwind
the tape and remove the probe from
the protective glass tube. Only the
bulbous tip is sensitive to
potassium. For best results, soak
the tip of the electrode in 0.1 N
KCl solution for 24 hours prior to
use.
The use of a
separate Reference Electrode such as
our MI-409F is required.
Calibration
Meter requirement:
Any research grade pH meter with
millivolt mode capability. Set
meter to millivolt mode.
The
MI-442 is standardized using pure
potassium chloride (KCl) solutions
and again in solutions containing
possible interfering ions ( if
appropriate). The pure KCl
solutions are used to determine
probe function. In pure solutions,
a 55 mv difference (approximate)
will occur between each tenfold
change in concentration. For
example, test in 0.001 N KCl, 0.01 N
KCl and 0.1 N KCl.
Standardization in solutions
containing possible interfering ions
is done in order to simulate the
actual samples to be analyzed. For
example, if your samples contain a
known sodium background such as 150
millimoles NaCl then your
calibrating standards should also
have this background.
Remember! For best results,
do the following:
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Always use standards that
bracket the concentration range
that you expect to have in your
samples.
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Always mix your standards to
closely match the composition of
your samples.
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Always calibrate using the same
volume of standard that you will
have as a sample.
Example: samples = 50 microliters
then standards = 50 microliters.
Handling
Always handle the electrode with the
same care you would use with other
glass electrodes.
Cleaning
When using the electrodes in
solutions containing protein, the
MI-442 and the reference electrode
should be rinsed with an enzyme
cleaning solution such as Terg-a-zyme
(Alconox,
Inc.) or a chromic/sulfuric
glass cleaning solution after each
use for a couple of minutes to
remove the protein from the glass
and the reference junction. This
will prolong the useful life of the
electrodes.
These are some possible mixtures
you could use:
0.001N KCl-0.15 N NaCl, 0.01N
KCl-0.15 N NaCl, 0.1N KCl-0.15 N
NaCl. The data are then plotted on
semilog paper
(See Sample Calibration Curve).
Storage
Always clean the microelectrode
before storing:
Long-term (over 2 weeks):
Return the electrode to its original
container and prepare it in the same
condition is which you received it.
Usually this means simply moistening
the sponge located in the bottom of
the protective glass tube with
distilled water.
Short-term: The
electrode can be left in a 0.1 N KCl
solution.
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