1.1 Methods
Notes:
1. The same batch of SPADNS reagent solution must be used for adjustment and test.
The adjustment process needs to be performed for each new batch of SPADNS reagent
solution (see Standard Methods 20th, 1998, APHA, AWWA, WEF 4500 F D., S. 4-82).
The procedure is described in chapter 2.4.5 “Calibration – Fluoride Method 170“ on
page 234.
2. During adjustment and test the same vial should be used for zeroing and test, as
different vials may exhibit minor tolerances.
3. The calibration solution and the water samples to be tested should have the same
temperature (± 1°C).
4. As the test result is highly dependent on exact sample and reagent volumes, the sample
and reagent volumes should always be metered by using a 10 ml resp. 2 ml volumetric
pipette (class A).
5. The accuracy of the test methods decreases above a level of 1.2 mg/l Fluoride. Although
the results are sufficiently accurate for most applications, even more exact results can be
achieved by 1:1 dilution of the sample prior to use and subsequent multiplication of the
result by 2.
6. SPADNS reagent solution contains Arsenite.
Chlorine concentrations up to 5 mg/l do not interfere.
7. Seawater and wastewater samples must be distilled.
8. It is convenient to use special vials with larger volume.
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