Comparison of the performance of flexural plate wave and surface acoustic wave devices as the detector in a gas chromatograph

The sensitivity to chemical vapors of the flexural plate wave (FPW) device is compared to that of a 250 MHz surface acoustic wave (SAW) detector available with the MSI-301 Gas Chromatograph. The sensitivity of uncoated devices, and devices coated with the polymeric adsorbents polyisobutylene and polybutadiene, were compared using three vapors-methanol (CH₃OH), nitrous oxide (N₂O), and helium (He). Both the SAW and FPW sensor responses were linearly proportional to concentration with concentration. The FPW is shown to be more sensitive than the SAW for all three vapors, regardless of coating. The minimal detectable concentrations for methanol, N₂O and He were 75 ppm, 80 ppm, and 250 ppm respectively, for the FPW, and 535 ppm, 2500 ppm, and greater than 10000 ppm for the SAW. The relatively high sensitivity of the FPW is attributed to its response to both mass loading and changes in gas density