10
11
stabilized. This value should be less than the previ-
ous 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 4010).
•
Verify plastic film has been removed from inner stem
(HI 4110 or HI 5315 electrode).
•
Verify electrodes are connected properly to meter and
meter is powered. For HI 4110 verify sensor is screwed
into the inner stem.
•
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 standard may solve
the problem. (Choose 10
-2
M fluoride or 1000 ppm
standard).
•
A scratched sensing surface can be polished with fluo-
ride toothpaste (without baking soda). Use a small
drop of the paste and a soft wipe. Using a circular
motion, and gentle pressure, rub the surface of the
electrode with this micro abrasive material. Rinse
with water. Check to see if small scratches have been
eliminated. Rinse in deionized water and blot dry.
Soak in a fluoride standard for 1 hour. Repeat section
IX.
•
If the reading is jumpy or unstable, shake sensor
down (see section VIII).
•
If the membrane is damaged, the response becomes
extremely sluggish, or the slope of the electrode has
decreased significantly, and procedures above have
not helped, the sensor (or module) should be re-
placed.
10. Tighten the electrode cap onto the body and fill elec-
trode body until fill solution volume is just below fill
hole.
11. Position electrode in a Hanna HI 76404 electrode
holder (or equivalent) and connect plug to meter.
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 deionized water into a beaker with
stir bar.
•
Place the electrodes 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
9. Holding the body of the electrode gently press upper
cap with your thumb. This permits the fill solution to
drain out of the body. Release cap and verify elec-
trode returns to its original position (you may need to
gently assist for this to occur).
HI
41
10
FLUORIDE
COM
BINA
TION
