T/CAIA SH002-2014 Drinking water fluoride determination using 2-(p-sulfobenzeneazo)-1,8-dihydroxy-3,6-naphthalenedisulfonic zirconium spectrophotometric method

Scope

Scope: This standard specifies the method for determining the fluoride content by spectrophotometry using 2-(o-sulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonic acid zirconium. This standard is applicable to the determination of fluoride (calculated as F-) in drinking water ranging from 0.28 mg/L to 1.6 mg/L. For a water sample containing 1.0 mg/L fluoride (calculated as F-), the interference ion concentrations that cause an error of 0.1 mg/L are as follows: Al3+ (0.1 mg/L), Cl- (7000 mg/L), NaPO3 (1.0 mg/L), SO42-(200 mg/L), PO43- (16 mg/L), Fe (10 mg/L), and alkalinity (calculated as CaCO3, 5000 mg/L). Main technical content: The 2-(o-sulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfonic sodium (SPADNS) forms a red zirconium dye with zirconium ions. In an acidic solution, fluoride ions react with the red zirconium dye, quantitatively displacing the zirconium in the dye, causing the dye to fade. The degree of fading is linearly related to the fluoride ion concentration within a certain range. The absorbance is measured at a wavelength of 600 nm on a spectrophotometer. The mass concentration of fluoride (calculated as F-) is then calculated.

Development Information

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