Analytical assays based on chromogenic and fluorogenic chemosensors for the detection of cyanide

Cyanide (CN-) is an anion well-known for its toxicity, being a chemical agent often related to cases of homicide and suicide. Despite being responsible for the toxicity of many animals and plants, it is used in several industrial activities, with innumerous implications in terms of the environment. Due to its high toxicity, the maximum level of CN- concentration allowed by the World Health Organization in potable water is 1.7 mu mol/L. This low concentration limit requires methods of visual detection and quantitative determination which are ever more sensitive, simple, reliable, and economical. Advancements in the field of chromogenic and fluorogenic chemosensors for anionic analytes have led to the development of several methodologies for the detection of CN-. Therefore, this review aims to present the main strategies that have been used in the study of quantitative and naked-eye detection of CN- by means of chromogenic and fluorogenic chemosensors. Aspects related to CN-, such as its reactivity, toxicity, applications, and implications in different domains of knowledge, are presented. Recent work involving the development of chemosensors for CN- based on acid-base reactions, chemodosimeters, chromoreactands, and competition assays is also described. In addition, recent studies that make use of nanotechnology to develop strategies for the detection of CN- are also discussed, as well as the prospects envisioned in this field.