Cavitands as superior sorbents for benzene detection at trace level

We present an innovative dynamic headspace-based approach to sampling of BTX using molecular receptors. For this purpose methylene-bridged (MeCav) and quinoxaline-bridged (QxCav) cavitands were silylated at the lower rim and grafted onto silica gel. In the case of QxCav, the resulting sorbent material selectively retains BTX at ppb levels in the adsorption phase and delivers a benzene-enriched fraction in the desorption phase. Under the same conditions, commercial sorbents like Carbotrap 100(R) and Tenax TA(R) proved to be unselective both in the uptake and in the release steps. The molecular origins of the observed selectivity were traced by theoretical calculations in the presence of multiple electrostatic and CH-pi interactions, possible only in the case of QxCav aromatic analyte complexes.