Determination of cyanide by a pervaporation–UV photodissociation–potentiometric detection approach

Abstract

An automated system for the determination of total cyanide in water samples was developed. Stable metal–cyanide complexes such as Fe(CN)₆³⁻ are photodissociated in an acidic medium with a UV lamp. The released hydrogen cyanide (HCN) is pervaporated and collected in dilute NaOH solution acting as an acceptor. The cyanide ion is isolated from interferents such as sulfide and determined potentiometrically using an ion-selective electrode. The content of cyanide in three wastewater samples obtained with the new method was compared with the results provided by the EPA method OIA-1677 for the determination of total cyanide in water samples. Excellent agreement was obtained in all instances. The method can be applied over a wide range of concentrations (0.4–200 μg l⁻¹ CN⁻ and 0.05–50 mg l⁻¹ CN⁻ using injection volumes of 200 and 50 μl, respectively). The sample throughput of the system is 40 h⁻¹ and the detection limit for total cyanide is 0.01 μg l⁻¹.