氣相層析儀結合微型發音哨對氣體分析的開發與研究

Abstract

本研究利用微型哨式發音器(milli-whistle)結合氣相層析儀(gas chromatography, GC)，並使用麥克風為偵測器，將毛細管柱之載流氣體與外加輔助的鞘流氣體混合後，偵測混合氣流以受迫性的高速通過哨式發音器時的單頻聲音。此時，聲音藉由麥克風接收並同步以 LabVIEW (Laboratory Virtual Instrument Engineering Workbench)程式進行快速傅立葉轉換(fast Fourier transform, FFT)，獲得即時聲音頻率，並探究頻率變化與分子量大小等對頻率影響的公式計算和探討。在最佳化實驗條件下頻率訊號半高寬約為 1.6 Hz，並以層析時間與即時發音哨之頻率作圖，即得氣相層析譜圖。與實驗結果比對後，發現不僅能成功地驗證理論推導公式，更可以應用在各式氣體樣品之中。透過本研究開發之理論公式可推估氣體樣品含有的氣體組成成分及含量，搭配分析物的滯留時間與頻率訊號的檢量線驗算，將能更精確地進行樣品的定性和定量研究。本研究進行檢測健康人體志願者之呼氣中含二氧化碳/氧氣比例、固相微萃取法(solid-phase microextraction, SPME)檢驗丙酮蒸氣的含量，以及硼烷氨類釋氫量與金屬酵素(metalloenzyme)釋氫量的理論計算，都得到與實際值或理論值相近的計算結果。此外，哨式發音器的製作有許多方法，本研究也比較了各種不同的構型，發現對於哨式發音器的感度和發聲頻率有很大的影響。

This study is conducted to a general understanding of the use of a milli-whistle as a gas chromatography (GC) detector in gas analysis, including on the methodology and theory associated with a number of different related applications. The milli-whistle is connected to the outlet of a GC capillary, and when the eluted gases and the GC carrier gas pass through it, a sound with a fundamental frequency is produced. The sound wave can be picked up by a microphone, and after a fast Fourier transform, the online data obtains for frequency-change vs. retention time constitute a new method for detecting gases. The first part discusses the fundamentals of the milli-whistle. Some modifications are also discussed, including various types of whistles and an attempt to maximize the sensitivity and stability of the method. The following part focuses on several practical applications, including an analysis of the CO2/O2 ratio from expired human breath, hydrogen released amount with theoretical calculation from ammonia borane and metalloenzyme, and a solid phase micro-extraction (SPME) test for acetone. These studies show that the GC-whistle method has great potential for use as a fast sampling ionization method, and for the direct analysis of biological and chemical samples under ambient conditions.