Abstract

A spectrofluorimetric method has been developed for the determination of free CN− in real samples with fluorescent safranine-O. When safranine-O interacts electrostatistically with CN−, the fluorescent intensity of safranine-O is decreased. Several experimental conditions such as pH of the sample solution and the amount of safranine-O were optimized. Ag+ interfered higher than any other ions. Interference of Ag+ could be disregarded because Ag+ was scarcely contained or mostly complexed with CN− in selected real samples. With this proposed method, the linear range of CN− was from 5.0 to 110 ng/mL and the detection limit of CN−was 2.9 ng/mL. For validating this technique, real samples (Cu, Ag, Au electroplating wastewater, and untreated wastewater in university and in sewage treatment plant) were used. Recovery yields of 91.5%~106.0% were obtained. Based on experimental results, it is proposed that this technique can be applied to the practical determination of free CN−.