Fluoride
Fluoride
Fluoride_AccuVac_Other_SPD_Eng_Ody.fm Page 3 of 6
Interferences
This test is sensitive to small amounts of interference. Glassware must be very
clean (acid rinse before each use). Repeat the test with the same glassware to
ensure that results are accurate.
Distillation
1. Most interferences can be eliminated by distilling the sample from an acid
solution as described below:
2. Set up the distillation apparatus for general purpose distillation. Refer to the
Distillation Apparatus manual for proper assembly. Use a 125-mL Erlenmeyer
flask to collect the distillate.
5. Touch the timer icon.
Touch
OK.
A one-minute reaction
period will begin.
6. When the timer
beeps, place the blank
into the cell holder.
7. Touch Zero.
The display will show:
0.00 mg/L F
–
8. Place the AccuVac
Ampul that contains the
sample into the cell
holder.
Touch
Read.
Results will appear in
mg/L F
–
.
Zero
Interfering Substance Interference Levels and Treatments
Alkalinity (as CaCO
3
) At 5000 mg/L it causes a −0.1 mg/L F
–
error.
Aluminum
At 0.1 mg/L it causes a −0.1 mg/L F
–
error. To check for interferences from aluminum, read the
concentration one minute after reagent addition, then again after 15 minutes. An appreciable
increase in concentration suggests aluminum interference. Waiting 2 hours before making the
final reading will eliminate the effect of up to 3.0 mg/L aluminum.
Chloride At 7000 mg/L it causes a +0.1 mg/L F
–
error.
Chlorine
SPADNS Reagent contains enough arsenite to eliminate interference up to 5 mg/L chlorine. For
higher chlorine levels, add one drop of Sodium Arsenite Solution (Cat. No. 1047-32) to 25 mL of
sample for each 2 mg/L of Chlorine.
Iron, ferric At 10 mg/L it causes a −0.1 mg/L F
–
error.
Phosphate, ortho At 16 mg/L it causes a +0.1 mg/L F
–
error.
Sodium Hexameta-
phosphate
At 1.0 mg/L it causes a +0.1 mg/L F
–
error.
Sulfate At 200 mg/L it causes a +0.1 mg/L F
–
error.
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