First colorimetric sensor array for the identification of quaternary ammonium salts

A colorimetric sensor array based on supramolecular host–guest complexes has been developed for the identification and quantification of quaternary ammonium salts (QAS). QAS are ubiquitous undesirable compounds for which the identification of the individual compounds is not trivial and needs instrumental techniques. The sensor array developed by us is constituted by host–guest complexes formed by the inclusion of tricyclic basic dyes such as proflavine, acridine orange, thionin, and methylene blue inside the hollow space defined by cucurbit[n]urils with n =7 and 8. The operation of the sensor array has been demonstrated by differentiating 14 quaternary ammonium salts, some of them differing by a single carbon atom in the alkyl group. The detection limit concentration was 10−5 M and the system can also be used to quantify the concentration of the quaternary ammonium ion.