Turn‐off–on chemiluminescence determination of cyanide

A flow injection chemiluminescence (FI–CL) method was developed for the determination of cyanide (CN^?) based on the recovered CL signal by Cu²⁺ inhibiting a glutathione (GSH)‐capped CdTe quantum dot (QD) and hydrogen peroxide system. In an alkaline medium, strong CL signals were observed from the reaction of CdTe QDs and H₂O₂, and addition of Cu²⁺ could cause significant CL inhibition of the CdTe QDs–H₂O₂ system. In the presence of CN^?, Cu²⁺ can be removed from the surface of CdTe QDs via the formation of particularly stable Cu(CN)_n]^(n‐1)– species, and the CL signal of the CdTe QDs–H₂O₂ system was efficiently recovered. Thus, the CL signals of CdTe QDs–H₂O₂ system were turned off and turned on by the addition of Cu²⁺ and CN^?, respectively. Further, the results showed that among the tested ions, only CN^? could recover the CL signal, which suggested that the CdTe QDs–H₂O₂–Cu²⁺ CL system had highly selectivity for CN^?. Under optimum conditions, the CL intensity and the concentration of CN^? show a good linear relationship in the range 0.0–650.0 ng/mL (R² = 0.9996). The limit of detection for CN^? was 6.0 ng/mL (3σ). This method has been applied to detect CN^? in river water and industrial wastewater with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.