高分子弦振動式氣相層析感測器之原理開發

Abstract

本研究嘗試開發以機械波振幅變化為原理的新型態感測器，其原理是藉由一揚聲器發出特定振幅以及頻率的正弦波，並透過一高分子弦傳遞至另一端收音器上被電腦記錄，經傅立葉轉換後可得到該頻率之強度，藉由氣體分子接觸高分子弦的吸附行為，造成高分子弦之質量與機械性質改變，進而引起振幅衰減而被觀察出。而此感測器藉由不同的設計，可以將其串聯於大流量的動態氣體生成系統，其偵測下限最低可感測到59.6 ppm的Butyl acetate以及101 ppm的Toluene之有機揮發性氣體。此裝置串聯於氣相層析儀上作為感測器使用時，實驗中將七種不同官能基之有機氣體混和後注入，經管柱分離後可得到相對於各樣品的訊號峰，其LOD最低可測得0.5 μg的m-Xylene，並比較高分子弦在不同條件下其長度、粗細等對偵測特性的影響，同時對於操作頻率、讀取訊號等方法，加以探討。此感測器未來應用在氣相層析具有獨特的優點。目前已證實原理的可行性，靈敏度等提升方法則仍在研究中。This research reports the development of a novel acoustic sensor made by speaker, microphone, and polymer string, called polymer string vibration (PSV) gas sensor. The sound produced by speaker was propagated to microphone through a polymer string. A function generator was used to produce an electronic sine wave with fix frequency and amplitude. The signal was then converted to vibrational wave by speaker. This acoustic signal was be transmitted to microphone by the polymer string. The acoustic wave can easily be detected by the microphone. The data acquisition were processed by Fast Fourier Transform (FFT) and programmed built-in LabVIEW 8.5, we can obtain the magnitude of given frequency. When the organic vapor was in contact with the polymer string, the vapor sorption by polymer string will result in polymer’s mass and mechanical properties change, causing attenuation of vibration. When PSV sensor was connected to vapor gas generator system, the limits of detection were found to be 59.6(Butyl acetate) and 101 (Toluene) ppm. When the PSV sensor was a detector connected to GC. Testing samples include: ethyl acetate, benzene, toluene, butyl acetate, chlorobenzene, m-xylene. The limits of detection were found to be ~10μg for most gas sample. We has demonstrated a proof-of-concept work for PSV sensor. Future work will also focus on improve the sensitivities, selectivities, and make this device suitable for environmental monitoring application.