Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 164

mesh Shimalite W. The column and injection port temperatures were maintained at 140
and 250°C respectively. The nitrogen flow rate was 25ml minL −1 . The peak areas were
measured by a digital integrator.
Down to 3mg L −1 free cyanide can be determined in waste waters by this procedure
without interference from 100mg L −1 of ammonium, cadmium(II), chromium(VI),
fluoride, chloride, bromide, iodide, thiocyanate, nitrate, bicarbonate and phosphate. Lead
(II), zinc(II) and sulphide interfere at 100mg L −1 but do not interfere at 10mg L −1 .
2.23.13 Miscellaneous
Other techniques used for the determination of free cyanides in water samples include
ultraviolet spectroscopy as the Ni(CN) 4 2− complex [286], squarewave polarograph [287]
and conventional polarography. The sensitivity of the polarographic methods range
between 0.1mg [286] and 1µg [287] cyanide .
2.24 Cyanide (total)
Total cyanide includes free cyanide ions plus complexed metal cyanides, eg
ferrocyanides. The methods discussed in the previous section determine only free
uncomplexed cyanide. To determine uncomplexed plus complexed cyanide, ie total
cyanide, it is necessary prior to analysis to decompose the complexed cyanides to free
cyanide [288].
2.24.1 Atomic absorption spectrometry
Rameyer and Janauer [289] have described a method using reactive ion exchange for the
determination of complex iron cyanides in water in the mg L −1 range. The cyanide
complexes are preconcentrated on shallow beds of sulphonated cation-exchange resins in
copper(II) form by precipitation as copper hexacyanoferrate(II) or copper
hexacyanoferrate (III). Other cations, including contaminant iron species, are eluted with
hydrochloric acid. Aqueous ammonia relatively releases and elutes the hexacyanoferrate
by the formation of the copper ammine complex. Finally the complex cyanides are
determined as iron by atomic absorption spectrometry.
2.24.2 Ion selective electrodes
A procedure has been developed for determination of cyanide [290] in concentrations
down to 2mg L −1 by manual or automated potentiometry using a cyanide ion selective
electrode. Distinction is made between simple and complex cyanides by irradiation with
ultraviolet light.
2.24.3 Ion chromotogrophy
Rocklin and Johnson [291] have applied ion chromatography to the analysis of mixtures
of the complex cyanides of cadmium, zinc, copper, nickel, gold, iron and cobalt.