Hanna Instruments HI 4011 - Manual (Page 10)

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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 stir bar.
•
Place electrodes into prepared sample.
•
Add 1 mL of a standard 0.1 M (12690 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 less than the previous noted (more
negative).
•
Determine the difference between the two mV values.
An acceptable value for this slope is -56 ± 4 mV.
X. X. X. X. X. Corrective action Corrective action Corrective action Corrective action Corrective action
•
Verify protective cap has been removed (HI 4011).
•
Verify plastic film has been removed from inner stem
(HI 4111).
•
Verify electrodes are connected properly to meter and
meter is powered.
•
Verify dilute standards are freshly made and stored.
Remake solutions if appropriate.
•
If the sensor slope just misses the suggested slope
window, soaking the sensor in a dilute standard may
solve the problem. (
<10 -3 M Iodide or <126 ppm
standard).
•
A scratched sensing surface can be polished with HI
4000-70 polishing strip. Cut off approximately 1
inch of the micro-abrasive strip. Wet the frosted side
with deionized water
and place against damaged
membrane of the electrode. Place your thumb against
the shiny backing and slowly rotate back and forth
while applying gentle pressure. Continue polishing
until you are satisfied with the surface. If dark depos-
its appear on polishing strip move the paper slightly
and continue polishing.