Piezoelectric quartz crystal detection of benzene vapour using chemically modified cyclodextrins

Abstract

Three chemically modified cyclodextrins have been prepared, characterised by n.m.r. spectroscopy, and studied for their possible rôle as piezoelectric crystal coating detectors towards benzene vapour. 2,6-Per-O-methyl-β-cyclodextrin 3-perbenzoate (DMβCD-B<inf>7</inf>) is not recommended. 2,6-Per-O-(t-butyl-dimethylsilyl)-α-cyclodextrin (DSαCD) was found to be the best for the ca. 0.08 - ca. 400 mg dm ^-3 range of benzene vapour in air. 2,6-Per-O-allyl-α- cyclodextrin (DAαCD) is a possible alternative. Both detector systems function for > 20 days. The detectors are selective towards benzene vapour over methane, propane, butane, pentane, ethyne, ammonia, nitrobenzene, and toluene. Toluene gives rise to the most serious interference. For the preferred DSαCD sensor, toluene only gives <20% of the decrease in frequency observed with the corresponding amount of benzene. However, the interference is slightly greater for the DAαCD sensor.