Chromo- and fluororeactands: Indicators for detection of neutral analytes by using reversible covalent-bond chemistry

Chromo- and fluororeactands are indicator dyes that allow the optical detection of electrically neutral analytes. Unlike complexing agents such as calixarenes, cyclodextrines or cyclophanes, reactands form a reversible covalent bond with the analyte molecule. This chemical reaction causes strong changes in absorbance or fluorescence. In this article reactands for analytes such as amines, alcohols, aldehydes, saccharides, carbon dioxide and sulfur dioxide are presented. Methods to enhance the sensitivity of the reactands as well as the operational and shelf lives of the corresponding optical sensors are discussed.