Novel dicyanoargentate polymeric membrane sensors for selective determination of cyanide ions

The construction and general performance characteristics of three novel potentiometric PVC membrane sensors responsive to dicyanoargentate anion are described. The sensors are based on the use of magnesium(II)- and iron(II)-phthalocyanines as neutral ionophores and iron (II)-bathophenanthroline dicyanoargentate ion-pair complex as an ion exchanger in plasticized PVC matrices. These sensors exhibit fast, stable and near-Nernstian response (54-59 mV/ decade) for the singly charged dicyanoargentate anion over the concentration range 1 × 10^-2-5.8 × 10^-6 M. Potentiometric responses of sensors based on metal phthalocyanines and iron (II)-bathophenanthroline are stable over the pH ranges 5-7 and 5-12, respectively. The selectivity of the sensors are fairly good over most common anions. Use of the sensors for potentiometric determination of microgram quantities of cyanide ion after conversion into dicyanoargentate anions shows an average recovery of 99.5% and a mean standard deviation of ±0.5%. Determination of cyanide ions in some exhausted electroplating bath samples gives results that compare favourably well with data obtained using the solid-state cyanide electrode.