Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 226

(d) Diazotisation reagent: 4-aminosalicyclic acid

Coupling reagent: naphth-1-ol
Flamerz and Bashir [493] studied the effects of this method on foreign ions that often
accompany nitrite in water samples (Table 2.38).
The method is more selective towards anions than cations; this is not unexpected
because these azo dyes are commonly used chromogens for metal ions. However, an ion
exchange procedure can be used to remove the seriously interfering ions.

Table 2.38 Effect of diverse ions on the determination of nitrite

Interferent Permissible amount in the

presence of 10µg of nitrite (µg) a

Ammonia 150

Carbonate 50

Chloride 180

Cyanide 75

Fluoride 120

Iodide 140

Hydrogen carbonate 110

Nitrate 80

Phosphate 110

Sulphide 4

Sulphite 25

Calcium 60

Cadmium 9

Cobalt (II) 8

Copper(II) 10

Iron(III) 7

Magnesium 15

Mercury(II) 30

Lead(II) 30

Tin(II) 20

Phenol 170

a Amount of diverse ion causing an error of less than 2% in the determination
Source: Reproduced with permission from the Royal Society of Chemistry [493]