Sensing of halogenated aromatic hydrocarbons in water with a cavitand coated piezoelectric device

•Design and synthesis of a new quinoxaline cavitand functionalized at the upper rim with a bithiophene moiety suitable for electropolymerization.•Functionalization of a Piezoelectric Quartz Crystal (PQC) through electropolymerization of a quinoxaline cavitand.•The coating of the PQC transducer provides a highly sensitive and reproducible sensor for in-flow detection of aromatic hydrocarbons in water.•Excellent limit of detection (0.17 ppm) is achieved for 1,2,4-trichlorobenzene, outperforming conventional systems.