Abstract
本研究主要是發展出一套大氣環境中揮發性還原態硫化物的採樣以及分析方法。空氣樣品利用Tenax TA固態吸附劑取樣管配合低溫冷凍的方法採集，以經過改裝的熱脫附儀進行冷凍濃縮熱脫附前處理後，於線上將樣品導入氣相層析儀毛細管柱中分離，最後再以硫化學發光偵檢器偵測。分析管柱為30m x 0.32mm i.d.，4mm膜厚的Quadrex 007系列毛細管柱，分離樣品包含沸點範圍在-63 ~ 200℃間的28種硫化物，層析分離時間約為35分鐘。本研究中首度利用無火焰式硫化學發光偵檢器與火焰游離偵檢器串聯同步偵測樣品中的硫化物以及碳氫化合物圖譜，突破偵檢器串聯時第一個偵檢器必須為非破壞性偵檢器的限制。本研究中並以一級硫醇作為使用硫化物選擇性偵檢器時滯留指標的參考物種，建立26種高揮發性及半揮發性硫化物在線性昇溫條件下的滯留指數。低溫採樣時水汽造成嚴重的波峰分裂以及滯留時間漂移的問題，本實驗中利用Retention Gap的概念，在管柱前端加裝一段內徑0.53mm的去活化管柱，可有效解決波峰分裂的問題，在常溫下相對濕度80%以下採集1公升空氣樣品時，可將硫化氫以及甲基硫醇滯留時間漂移控制在5%以內，對於沸點高於乙基硫醇的樣品滯留時間漂移則可控制在1%以內。本研究另一個主題是利用長度400cm的毛細管柱分離硫化物樣品，以最佳效能(Performance)的概念探討縮短分析時間並達到最佳化分離。研究中主要探討管柱外效應引起的波帶變寬效應以及儀器常數與管柱長度的關係，用以預測在定溫條件下不同管柱長度的理論板高與線性流速關係，並藉由理論計算最短分析時間。經由最佳化探討將一組包含甲基硫醇的7種硫化物樣品由原先的12分鐘總分析時間縮短到2.6分鐘，另外將22種硫化物以昇溫條件在11分鐘內分離。The main goal of this study is to develop a sampling andanalysis system for the atmospheric reduced sulfur compounds.Atmospheric samples are cryogenically collected in a samplingtube filled with Tenax TA adsorbent. Samples are pretreated on amodified thermal desorber with a cryogenic/ thermal desorptionprocess, and on-line transferred to the capillary gaschromatograph for sample separation and then detected with asulfur chemiluminescence detector(SCD). The analytical column is30m x 0.32mm i.d., 4mm film thickness, Quadrex 007 seriescapillary column, 28 sulfur samples in which boiling pointranged from -63 ~ 200℃are separated within 35 minutes. In thisstudy, a flameless SCD and a flame ionization detector iscoupled in series for simultaneous detection of both sulfur andhydrocarbon chromatograms. This configuration violates the limitthat the first detector in a series-coupled detectors systemshould be a non-destructive ones. Using the n-alkylthiols asthe reference standards, the retention indices of twenty-sixvolatile and semi-volatile sulfur compounds have beenestablished for sample identification. In a cryogenic samplingmethod, peak splitting and retention time shift in chromatogramscaused by the water are serious problems. In this study, basedon the concept of the retention gap, a 0.53mm i.d deactivatedcolumn is installed in front of the analytical column forsolving these problems. In a 1-L air sample with 80% relativehumidity collected at the room temperature, the relativeretention time shift can be controlled within 5% for H2S and CH3SH and 1% for those compounds of which boiling points aregreater than C2H5SH. Another topic of this study is to separatesulfur compounds in a short capillary column, shortened ofanalysis time and optimized separation are achieved by using theconcept of best performance. The band broadening caused by theextra-column effects and the relationship between instrumentalconstant and column length are investigated. The H-u plot of anycolumn length can be predicted and theoretical shortest analysistime can be calculated. Via the optimization process, theanalysis time of seven sulfur compounds is shortened from 12 to2.6 min, and 22 sulfur compounds are separated within 11 minutesusing a temperature programming condition.