微小化介電質氮氣電漿放射光譜應用於氣相層析偵測器之研製

Abstract

本研究成功發展出微小化介電質放電電漿裝置應用於氣體偵測，此微小電漿氣體偵測器的電極是以白金線四周包覆玻璃製作而成，且電極間距為200 μm。當在兩端電極連接高壓產生器，施加電壓8 kVp-p、頻率67 kHz正弦波形的交流電源，可在常壓環境下形成穩定電漿，電漿放電體積約為80.0 nL。本研究以氧氣、氫氣、空氣及氮氣四種氣體做為載流氣體進行測試，其中以氮氣作為背景氣體，最容易產生電漿。當有機揮發性氣體通過電漿區域時，有機物會與氮氣形成碳氮鍵，以光譜儀偵測放射光譜在384 nm的地方會有明顯光譜訊號產生。本研究也進一步探討流速、電壓、採樣袋背景氣體與訊號反應的關係，氮氣電漿對於烷類、醇類、酮類、酯類、芳香族及鹵化物等各種官能基有機氣體通過時，在光譜儀上皆有類似的訊號反應，並且會隨有機氣體碳鏈的長度增加放射光譜的訊號強度。在本研究的測試系統中，偵測極限已達到0.54 ng，此裝置具備微小、價格低廉、不耗損電極、可使用成本較低的氮氣作為載流氣體以及高靈敏度等優點。A micro dielectric barrier discharge (DBD) plasma device has been developed for gas chromatograph detector. The micro plasma device electrode employed a pair of platinum wires (100 μm diameter) which were sealed inside a glass tube. The distance between these two electrodes was less than 200 μm. A high-voltage alternating current (AC) sine waveform of 8 kVp-p and frequency of 67 kHz was applied to the electrodes stable plasma was generated under atmospheric pressure. The volume of plasma discharge region was smaller than 80.0 nL. In the study, we tested four background gases of oxygen, hydrogen, air and nitrogen and nitrogen had lowest breakdown voltage to form plasma. The volatile organic compounds react with nitrogen ion to form carbon-nitrogen bonds when they passed through the plasma region. The spectrometer detected carbon-nitrogen bonds emission spectrum at 384 nm. The study further investigates the correlation of flow rate, voltage and different background gas in tedlar bags to detector respones. The spectrometer had similar emission spectrum when volatile organic compounds passed through the plasma region such as alkanes, alcohols, ketones, esters, aromatic halides of various functional groups, and the emission spectrum intensity increase with alkanes carbon chain length to increase. The estimated limit of detection (LOD) was 0.54 ng for 2-heptanone. This μ-plasma device is an extremely small, inexpensive, no electrode erosion, and can operate under lower cost nitrogen with high sensitivity.