利用氣相層析儀結合加速規及麥克風氣體感測器線上定量檢測硼烷氨的氫氣釋放濃度

Abstract

本研究首次使用加速規 (accelerometer)作為氣相層析儀 (gas chromatography; GC) 的氣體感測器。將微型哨 (milli-whistle) 連接於氣相層析管柱出口端，當管柱層析物與鞘流氣體通過哨式偵測器時便會發出聲音，產生的聲頻可以用麥克風接收，哨子的振動則由加速規測量，再透過快速傅立葉轉換 (fast Fourier transform; FFT) 即可得到頻率。分析物選擇加熱時能夠釋放氫氣的儲氫材料硼烷氨 (ammonia borane; NH3BH3)。實驗結果顯示，無論是聲波或微型哨身的振動，所產生的頻率是相同的。根據頻率的變化量線上即時測定氫氣的釋放濃度。本實驗使用自組裝電磁閥注射裝置，將硼烷氨放置在注射裝置的樣品槽內加熱，釋放的氫氣以 0.5 分鐘為間隔注入 GC 分離系統，可以即時定量每次注入的氫氣濃度。研究中發現以靜電紡織技術，將硼烷氨包覆在聚碳酸酯纖維 (polycarbonate; PC) 的微管陣列薄膜中，可以降低釋放氫氣所需的溫度，這將使得儲氫材料的適用性更為廣泛。研究結果，每 1.0 mg 的硼烷氨在溫度範圍 85 - 115 ℃中可以產生的氫氣量為 1.0 ~ 1.25 mL。

The use of an accelerometer as a gas detector in gas chromatography (GC) is described for the first time. A milli-whistle was connected to the outlet of the GC capillary. When the eluted and GC carrier gases pass through the capillary and milli-whistle, a sound is produced. After a fast Fourier transform (FFT), the sound wave generated from the milliwhistle is picked up by a microphone and the resulting vibration of the milliwhistle body can be recorded by an accelerometer. The release of hydrogen gas, as the result of thermal energy, from ammonia borane (NH3BH3), which has been suggested as a storage medium for hydrogen, was selected as the model sample. The findings show that the frequencies generated, either by sound or by the vibration from the whistle body, were identical. The concentration levels of the released hydrogen gas can be determined online, based on the frequency changes. Ammonia borane was placed in a brass reservoir, heated continually, and the released hydrogen gas was directly injected into the GC inlet at 0.5 min intervals, using a home-built electromagnetic pulse injector. The concentration of hydrogen for each injection can be calculated immediately. When the ammonia borane was encapsulated within a polycarbonate (PC) microtube array membrane, the temperature required for the release of hydrogen can be decreased, which would make such a material more convenient for use. The findings indicate that 1.0 mg of ammonia borane can produce hydrogen in the range of 1.0−1.25 mL, in the temperature range of 85−115 °C.