Selective separations by reactive ion exchange: Part II. preconcentration and determination of complex iron cyanides in waters

Reactive ion exchange has been applied to the determination of p.p.b. concentrations of hexacyanoferrate(II) and hexacyanoferrate(III) in various water matrices. The in situ precipitation of copper hexacyanoferrate(II) or hexacyanoferrate(III) preconcentrates the complex cyanides on shallow beds of sulfonated cation-exchange resin in the copper(II) form. Hydrochloric acid reactively elutes other cations including concomitant iron species from the resin bed and, finally, aqueous ammonia reactively releases and elutes the hexacyanoferrate(II) (or III) species through the formation of the copper-ammine complex. Preconcentration factors of 100 or more are possible when 1-1 samples are used. Final determination of the complex cyanides is performed by atomic absorption spectrometry (for iron).