Fluoride L / M170
SPADNS Method for Fluoride Determination
Instrument Specific Information
The test can be performed on the following instruments. The required cuvette and the absorption range of the photometer are also indicated.
| Instruments | Cuvette | Wavelength (λ) | Measurement Range |
|---|---|---|---|
| MD 100, MD 600, MD 610, MD 640, MultiDirect, Spectro-Direct, XD 7000, XD 7500 | Ø 24 mm | 580 nm | 0.05 - 2 mg/L F |
Reagents
Required materials (partially optional):
| Reagent | Packaging Unit | Order Number |
|---|---|---|
| SPADNS Reagent Solution 250 ml | 250 mL | 467481 |
| SPADNS Reagent Solution 500 ml | 500 mL | 467482 |
| Calibration Standard Fluoride | 30 mL | 205630 |
Application Areas
- Drinking water treatment
- Purification of polluted water
Preparation
- Before measurement, perform user calibration (refer to photometer instructions).
- Use the same SPADNS reagent solution batch for user calibration and sampling (refer to photometer instructions). The instrument must be calibrated for each new batch of SPADNS reagent solution (see Standard Methods 20th, 1991, APHA, AWWA, WEF 4500 F D., S. 4-82).
- For user calibration and measurement, the zero adjustment and the test must be performed using the same cuvette, as cuvettes have small tolerances relative to each other.
- The calibration solutions and water samples to be measured must have the same temperature (± 1 °C).
- The analysis result depends primarily on the exact sample and reagent volume. Use only a 10 ml or 2 ml graduated pipette (Class A) to dispense the volume of the sample and reagent.
- Seawater and wastewater samples must be distilled.
- It is recommended to use special cuvettes with a larger fill volume.
Execution of Fluoride Determination with Liquid Reagent
Select the method in the instrument. For the following instruments, a zero measurement is not required each time: XD 7000, XD 7500. Observe the notes!
Step 1: Sample Preparation
Fill a 24 mm cuvette with exactly 10 mL of sample.
Close the cuvettes. [close-icon]
Place the sample cuvette in the measuring chamber. Pay attention to positioning. [position-icon]
Step 2: Zero Adjustment
Press the ZERO button. [zero-button-icon]
Remove the cuvette from the measuring chamber.
For instruments that do not require a zero measurement, start here.
Step 3: Reagent Addition
Fill a 24 mm cuvette with exactly 2 mL of SPADNS Reagent Solution. Note: Fill the cuvette to the brim! [fill-icon]
Close the cuvettes. [close-icon]
Step 4: Mixing and Measurement
Mix the contents by swirling. [swirl-icon]
Place the sample cuvette in the measuring chamber. Pay attention to positioning. [position-icon]
Press the TEST (XD: START) button. [test-button-icon]
The display shows the result in mg/L Fluoride.
Chemical Method
SPADNS
Appendix
Calibration Function for Third-Party Photometers
Conc. = a + b•Abs + c•Abs² + d•Abs³ + e•Abs⁴ + f•Abs⁵
| Coefficient | Ø 24 mm | 10 mm |
|---|---|---|
| a | 8.44253 10+0 | 8.44253 10+0 |
| b | -1.41844 10+1 | -3.04965 10+1 |
| c | 9.24803 10+0 | 4.2749 10+1 |
| d | -2.3046 10+0 | -2.2904 10+1 |
| e | ||
| f |
Interferences
Permanent Interferences
1. Accuracy decreases above 1.2 mg/L fluoride. Although the results are sufficiently accurate for most applications, better accuracy can be achieved by diluting the sample 1:1 before use and multiplying the result by 2.
Interferences
| Interference | Interferes from |
|---|---|
| Cl₂ | 5 mg/L |
Literature References
Standard Methods 20th, 1992, APHA, AWWA, WEF 4500 F D, S. 4-82
Conformity
US EPA 13A
APHA Method 4500 F D
