Detection of polar organic vapours with piezoelectric crystals coated with crown ethers

An oscillating piezoelectric crown-ether-coated quartz crystal membrane detector with a computer interface for signal processing was prepared to detect polar organic vapours. The piezoelectric crown ether/quartz membrane detector exhibited high sensitivity with a frequency shift range of 10-340 Hz/(mg/l) for organic gases, a short response time (< 2.0 min), good selectivity and good reproducibility for reusage. Several coatings on quartz membrane crystals based on benzo-15-crown-5 and cryptand-22 were made for responses to organic amines, alcohols, ketones, halides, carboxylic acids and sulfides. Benzo-15-crown-5 functioned as a sensitive coating for alcohols, amines and organic sulfides whereas cryptand-22 was sensitive to amines and carboxylic acids. Steric effects and isomer effects on frequency shifts of the quartz crystal detector based on benzo-15-crown-5 for alcohols and amines were also investigated.