EPA Method 340 1
EPA Method 340 1
EPA Method 340 1
1974,
1978)
INSTRUMENTATION: Spectrophotometer
2.1 Following distillation to remove interferences, the sample is treated with the
SPADNS reagent. The loss of color resulting from the reaction of fluoride with
the zirconyl- SPADNS dye is a function of the fluoride concentration.
3.0 Comments
3.1 The SPADNS reagent is more tolerant of interfering materials than other
accepted fluoride reagents. Reference to Table 414:1, p 388, Standard Methods
for the Examination of Waters and Wastewaters, 14th Edition, will help the
analyst decide if distillation is required. The addition of the highly colored
SPADNS reagent must be done with utmost accuracy because the fluoride
concentration is measured as a difference of absorbance in the blank and the
sample. A small error in reagent addition is the most prominent source of
error in this test.
3.2 Care must be taken to avoid overheating the flask above the level of the
solution. This is done by maintaining an even flame entirely under the boiling
flask.
4.0 Apparatus
5.0 Reagents
6.0 Procedure
7.0 Calculations
7.1 Read the concentration in the 50 mL sample using the standard curve (6.2.4)
7.2 Calculate as follows:
7.3 When a sample (mL sample) is diluted to a volume (B) and then a portion (C)
is analyzed, use:
Bibliography
1. Standard Methods for the Examination of Water and Wastewater, p. 389-390 (Method
No.414A, Preliminary Distillation Step) and p. 393-394 (Method 414C SPADNS) 14th
Edition, (1975).
2. Annual Book of ASTM Standards, Part 31, "Water", Standard D 1179-72, Method A, p.
310 (1976).