Multianion analysis, miscellaneous methods - Determination of Anions in Natural and Treated Waters - page 716

14.1.2 Aqueous precipitation
14.1.2.1 Nitrate, sulphate and phosphate
Faigle and Klockow [3] applied gas chromatography to the determination of traces of
nitrate, sulphate and phosphate in rain water. The dissolved salts are freeze-dried and
converted to the corresponding silver salts. These are then converted to n -butyl esters
with the aid of n -butyl iodide, the n -butyl esters being determined by direct injection into
a gas chromatographic column. Sulphate and phosphate may be determined
simultaneously on a column containing 3% OV-17 on Chromosorb G, while nitrate is
determined separately with 3% tri- p -cresylphosphate as the stationary phase on a similar
support.
14.1.2.2 Chloride, bromide and iodide
Mack and Grimsrud [4] have described a photochemical modulated pulsed electron
capture detector suitable for the gas chromatographic determination of chloride, bromide
and iodide in rainwater.
14.1.3 Potable waters
14.1.3.1 Chloride, bromide and iodide
Bachmann and Matusca [5] have described a gas chromatographic method for the
determination of µg L −1 quantities of chloride, bromide and iodide in potable water. This
method involves reaction of the halide with an acetone solution of 7-oxabicyclo-(4.1.0)
heptane in the presence of nitric acid to form halogenated derivatives of cyclohexanol
and cyclohexanol nitrate. The composition of the reagent is 1% 0.1N nitric acid 7-
oxabicyclo-(4.1.0) heptane, 25% water, 75% acetone. The column effluent passes
through a pyrolysis chamber at 800°C and then through a conductivity detector. The
solution is injected onto a gas chromatographic column (OV-10-Chromosorb W-HPl 80-
100 mesh), 150cm long, 0.2cm diameter, operated at 50°C Hydrogen is used as carrier
gas. Chloride contents determined by this method were 5.0 ± 1.5µg L −1 in potable water.
Grandet et al. [6] have described a method for the determination of traces of bromide
(and iodide) in potable water which permits determination of 50µg bromide L −1 and 5µg
iodide L −1 without preconcentration of the sample, or 0.5µg bromide L −1 and 0.2pg iodide
L −1 after preconcentration. The method is based on the transformation of the halides into
2-bromo- or 2-iodo-ethanol. These derivatives are extracted with ethyl acetate and
determined with an electron capture detector. The difference in the retention periods
enables both halides to be determined simultaneously in one sample. The method is
substantially free of interferences and is suitable for use on many types of water.