Chromogenic Chemosensors Based on Phenolic Imines for the Detection of Alkylamines and Lidocaine in Water and in the Vapor Phase

Three imines comprised of 5-nitrothiophen-2-yl as electron-accepting and phenols as electrondonating groups were synthesized and used as chromogenic chemosensors to detect alkylamines. The compounds are colorless in water, but their deprotonation by the alkylamines generates the corresponding colored phenolates, which can be used to detect those analytes. The addition of cetyltrimethylammonium bromide (CTAB) causes bathochromic shift of the perichromic band of the phenolates, indicating that the compounds are transferred into the micelles. In addition, CTAB lowers the pKa of phenols and increases the stability of the phenolates, improving their performance as chemosensors. Applications were prospected with the chromogenic chemosensors adsorbed on strip papers to detect alkylamines in water and in the vapor phase. The compounds were also used in solution for the quantification of lidocaine in water. Thus, the versatility of the compounds studied allows to think about applications in industrial, environmental, and pharmaceutical areas.