Surface acoustic wave olefin/alkyne sensor based on Ag(I)/cryptand-22

A surface acoustic wave (SAW) sensor was prepared by using a 315 MHz one-port quartz resonator coated with a Ag(I)/cryptand-22 complex and a home-made computer interface for signal acquisition and data process, and was applied as a detector for gas chromatographic (GC) detection for various alkenes and alkynes. Effects of the kind and the amount of the coating materials were investigated. Among various metal ion/cryptand-22 complexes, Ag(I)/cryptand-22 was found to be the best coating as an adsorbent for alkene and alkyne molecules. The Ag(I)/cryptand-22-coated GC–SAW detector exhibited linear responses to 1-hexene and 1-hexyne. The comparison between SAW and quartz crystal microbalance (QCM) sensors demonstrated that the SAW sensor exhibited much better response than the QCM sensor. The frequency responses of the Ag(I)/cryptand-22-SAW sensor to normal C6 hydrocarbons were in the order of 1-hexyne > 1-hexene > hexane, while responses to various heptene isomers were in the orders of cis-2-heptene > trans-2-heptene and cis-3-heptene > trans-3-heptene. The molar mass effects examined for alkynes and alkenes indicated that the SAW detector was quite sensitive to the hydrocarbons with good reproducibility and quite low detection limits, e.g. 0.60 mg L−1 for cis-3-heptene. The performance of the Ag(I)/cryptand-22 SAW GC detector was well comparable to the commercial thermal conductivity detectors (TCD). The effects of flow rate and temperature on the response of the detector were also investigated and discussed.