Anions in wastewaters - Determination of Anions in Natural and Treated Waters - page 550

DIW 1.30 1.10

DIW 5.1 5.2

DIW 5.1 5.1

WW CA 0.06 0.06

WW CB 0.13 0.10

WW CC 0.31 0.29

WW BE 0.41 0.33

WW CD 0.66 0.64

WW CE 0.93 0.95

WW CF 0.96 0.97

WW CG 1.9 2.2

a DIW=deionised water; WW=wastewater
Source: Reproduced with permission from the American Chemical Society [54]

Czikai and Barnard [54] evaluated their procedure by adding both free cyanide and
complex metal cyanides to both deionised water solutions and wastewater samples
containing or spiked with nitrate and thiocyanate. The recovery of cyanide was virtually
complete. Typical findings for complex metal cyanides are presented in Table 8.18. For
the cyanide complexes of chromium, copper, iron and nickel, the recovery of cyanide was
usually greater than 95%. As mentioned previously, the failure to disrupt
hexacyanocobaltate(II) due to its kinetic inertness is a limitation of most total cyanide
procedures.
In Table 8.19 some results obtained by both the spectrophotometric and the cyanide
electrode potentiometric finishes are presented. The similarity of cyanide determinations
obtained by these two different procedures confirms that cyanide only is being
determined.

8.9.5 Gas chromatography

Complex cyanides have been determined gas chromatographically in amounts down to
100µg L −1 [59]. The complex cyanides are broken down by ultraviolet radiation, reacted
with bromine water and the cyanogen bromide formed is separated and determined
selectively by means of an electron capture detector.

8.9.6 Miscellaneous

Overbach [38] discussed problems encountered in the determination of low
concentrations of cyanide in photographic processing waste waters. Determination of
both total and free cyanide in the same sample differentiates between the toxic free
cyanide and the complexed ferrocyanide. Because of possible instability of the cyanide,
he recommended that samples should be analysed on-site, for instance by microdifusion