Table 12.1 Comparison of methods for the determination of fluoride in water samples
Method Reagent Precision
Accuracy
(based on
recoveries
from 'spiked'
samples)Interferences(1) spectrophotometric alizarin red-S 4 – 5%
preferably removed by ion exchange
or distillation
(2) spectrophotometric eriochrome cyanine R
(solochrome)
6 – 8%
(3) spectrophotometric SPADNS 4 – 5% aluminium is
the most
serious
(4) spectrophotometric alizarin-complexone ~3%
(5) potentiometric (fluoride
electrode)
— ~3% 100% readily complexed to release F(6) distillation–titration converted to H 2 SiF 6
(7) titration Th(NO 3 ) 4 alizarin red–S
indicatorNot evaluated(8) ion exchange–
spectrophotometric
beryllium salt, SPADNS