Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 220

in mineral waters. The method is based on the technique of isotopic dilution analysis. The
formation of negatively charged nitrite thermal ions from the nitrate in the water permits
the nitrate to be detected in the mass spectrometer. Using nitrogen-15 labelled nitrate as a
radioactive tracer for the isotopic dilution method,

Table 2.36 The effects of various interferences on the determination of nitrates by three
methods. For all determinations (with the exception of non saline river waters)
the concentration of NO 3 − N was 1.125mg L −1 . All concentrations are given in
mg L −1

Interference Phenoldisulphonic acid Method UV method Selective ion electrode

Uncorrected Corrected Uncorrected Corrected Uncorrected Corrected

Chloride

1.07 a 1.55 d

100 0.62 1.08 1.08

1000 1.05

Bicarbonate-carbonate
100 1.13 1.06 7.87

1.24 e

260 1.23

1000 1.13

Bicarbonate-chloride
100Cl:200HCO 3

1.58 e

100Cl:100HC0 3

1.46 e

50Cl:100HCO 3

1.46 e

Nitrate
0.304

1.11 1.48

1.10 b

1.31 e

1.500

1.06 b

3.0-4 1.13

Ammonium
1.4 0.98

1.13 e

14.0 0.66 1.08

1400.0 1.08

Interferences Phenoldisulphonic add Method UV method Selective ion electrode

Uncorrected Corrected Uncorrected Corrected Uncorrected Corrected

Phenol
1.0

1.10 c 1.13 c

1.10 1.29