6
7
VII.
VII.
VII.
VII.
VII. General Guidelines
General Guidelines
General Guidelines
General Guidelines
General Guidelines
•
During measurement always operate electrode with
the fill hole open.
•
Verify protective cap has been removed.
•
During normal use, fill solution will slowly drain out
of the ceramic junction located on the side of the the
electrode. Excessive loss (>2 cm drop within 24 hours)
is not normal.
•
Add fill solution daily to maintain a good head
pressure. For optimum reference response, this level
should be maintained and not be allowed to drop
more than 2-3 cm (1-inch) below fill hole.
VIII.
VIII.
VIII.
VIII.
VIII. Electrode Preparation
Electrode Preparation
Electrode Preparation
Electrode Preparation
Electrode Preparation
Before using the electrode for the first time or if reactivating
it after storage, the electrode should be conditioned, soaked
in storage solution and then tested.
For a new sensor:
Remove the protective shipping cap from the glass bulb
and save for storage.
Slide fill hole cover off opening to refill reference cavity
with HI 7079 fill solution. Leave open during measure-
ment.
Condition/etch sodium sensitive membrane:
Warning: Use extreme care when handling condtioning
solution. Protective gloves and eyeware should be worn.
This procedure removes a thin layer of sensitive glass from
the sodium membrane exposing a fresh surface. Pour a
small quantity of Hanna HI 4016-46 conditioning solution
into a plastic container. Place the sensing membrane (round
bulb at tip of sensor) into the solution for one minute.
Discard conditioning solution after use , do not return to
bottle. Rinse off sensor bulb in water and place into a
small container of storage solution (HI 4016-45). This so-
lution provides optimum conditions to rehydrate the mem-
brane surface and prepare it for sodium measurements. A
minimum of one hour is recommended for rehydrating the
sensing surface.
•
Calibration standards and sample solutions should
have the same ionic strength. ISA should be added to
both samples and standards immediately before tak-
ing measurements.
•
Calibration standards and sample solutions should be
at the same temperature. Thermally insulate solution
vessel from magnetic stirrer with cork or other insulat-
ing medium.
•
Calibration standards and sample solutions should
be stirred at the same rate using identical sized stir
bars.
•
Surface coating will effect the response. Inspect sen-
sor before using.
•
Rinse electrode with distilled or deionized water be-
tween samples and dab dry with lab wipe or other soft
disposable absorbent toweling.
•
Check calibration every 1-2 hours.
IX.
IX.
IX.
IX.
IX. Quick Check of Electrode Slope
Quick Check of Electrode Slope
Quick Check of Electrode Slope
Quick Check of Electrode Slope
Quick Check of Electrode Slope
•
Connect sensors to pH/mV/ISE meter
•
Place meter in mV mode.
•
Place 100 mL of DIW into a beaker with 10 mL ISA
and a stir bar.
•
Place electrode into prepared sample.
•
Add 1 mL of a standard (0.1 M or 1000 ppm stan-
dard) to beaker. Record the mV value when stable.
•
Add an additional 10-mL of standard to the solution.
Record the mV when reading has stabilized. This
value should be more positive than the previous noted
•
Determine the difference between the two-mV values.
An acceptable value for this slope is 56 ± 4 mV.