Anions in trade effluents - Determination of Anions in Natural and Treated Waters - page 590

10.5 Complex cyanides
10.5.1 Spectrophotometric method
In a method described by Drikas and Routley [28] a stoichiometric amount of lead acetate
is added to the sample to remove sulphide interferences. Addition of excess lead caused a
low recovery of cyanide. The stoichiometric amount of lead to be added was determined
by titration with lead acetate using a redox electrode for endpoint detection; cyanide
recoveries averaged 91%.
In a continuous Technican Autoanalyser method [29] for determining total cyanide ion
cyanide was reacted with pyridine-barbituric acid and the colour produced was evaluated
spectrophotometrically. Percentage recoveries from industrial waste samples spiked with
potassium ferricyanide and cyanide, respectively, were 98.9% and 100%.
10.5.2 Ion pair chromatography
Grigorova et al. [30] separated and determined stable metallo-cyanide complexes of
copper(II), silver(I), iron(II), cobalt(III), nickel(II), iron(III) and gold(I) in metallurgical
plant solutions by reversed phase ion-pair partition chromatography and ultraviolet
detection. The mobile phase contained 2.5mm tetrabutyl ammonium hydrogen sulphate
and methanol and the stationary phase consisted of carbon-18 Novapak cartridges with
4µm packing. Precision was good with relative standard deviation ranging from 1.1 to
2.8%.
10.6 Dithionate
10.6.1 Ion chromatography
Petrie et al. [31] applied this technique to the determination of dithionates in mineral
leachates. The application of this technique is also discussed under multianion analysis in
section 12.8.4.
10.7 Ferrocyanide
10.7.1 Spectrophotometric method
Ferrocyanides in coke plant effluents have been determined spectrophotometrically using
2,2 ′ -bipyridyl or 1,10-phenanthroline [32], The ferrocyanide is first broken down by
digestion with formaldehyde prior to the determination of uncomplexed iron.