21
METHOD PROCEDURE
• Press
Zero.
The display will show a 2 minute countdown prior to zeroing the blank.
To skip the timer, press
Zero
twice. The display will show “-0.0-” when the meter is
zeroed and ready for measurement.
• Remove the cuvette.
• Insert the second cuvette (#2) into the holder and ensure
that the notch on the cap is positioned securely in the groove.
• Press
Read
. The instrument displays the results in
mg/L
of
fluoride (F
-
)
.
Note:
For wastewater or seawater samples, before performing measurements,
distillation is required. For most accurate results use two graduated pipettes to
deliver exactly 8 mL of DIW and 8 mL of sample.
INTERFERENCES
Interference may be caused by:
• Alkalinity above 5000 mg/L CaCO
3
• Chloride above 700 mg/L
• Sulfate above 200 mg/L
• Orthophosphate above 16 mg/L
• Iron (Ferric) above 10 mg/L
• Sodium hexametaphosphate above 1.0 mg/L
• Aluminum above 0.1 mg/L
• Highly-colored and turbid samples may require distillation
• Highly-alkaline samples can be neutralized with nitric acid
# 2