Hanna Instruments HI 4009 - Manual (Page 10)

10
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
Use of a hood and protective clothing is strongly advised.
•
Connect sensors to pH/mV/ISE meter
•
Place meter in mV mode.
•
Place 100 mL of deionized water into a beaker with
stir bar and 1 mL of HI 4001-00 ISA.
•
Place electrodes into prepared sample.
•
Add 1 mL of the stock standard (either M or ppm) to
the beaker. Record the mV value when stable.
•
Add an additional 10 mL of stock 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 4009).
•
Verify plastic film has been removed from inner stem
(HI 4109).
•
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 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 gloved thumb
against the shiny backing and slowly rotate back and
forth while applying gentle pressure. Continue pol-
ishing until you are satisfied with the surface. If dark
deposits appear on polishing strip move the paper
slightly and continue polishing.