| 摘要: | 本研究利用丁式切換器(Deans’ switch)作為產生脈衝的方法，並結合自製之熱脫附裝置，開發出簡易型之全面二維層析技術，自行開發一套全面二維氣相層析裝置，其耐用性高且裝置簡單，可大幅降低購置與分析成本，不需採用專門分析方法與商業軟件成品。 本實驗針對若干常見的高揮發性VOCs 作為分析對象，以DB-1 作為 第一維管柱與PLOT 作為第二維管柱，利用兩種不同滯留特性的管柱進行正交化分析(orthogonality)，表現VOCs 熱脫附與GC×GC 上的獨特性，並利用丁式切換器產生脈衝，達全面二維氣相層析中調制(Modulation)的功能。利用自行發展的數據處理程序搭配商業繪圖軟體(Surfer 8)，將原始圖譜轉換成等值線圖(contour map)以呈現立體之分析的效果，並撰寫自動化程序來處理數據與繪圖。 實驗中發現遲滯效應(wrap-around)易造成偽層析峰的出現，產生層析上的錯覺。本實驗使用簡易方法來辨別遲滯效應所造成的偽層析峰，修飾後之等值線圖中可表現出正交性，不同物質類別出現群性，第一維以沸點大小差異分離，第二維以滯留力的強弱作再一次的展開，表現不同與以往常見GC×GC 中第一維以沸點大小與第二維以極性差異的分離方式；最終可定義出26 種分析物，包括於本實驗中仍為共析的2,3-dimethylbutane(NO. 16)、2-methylpentane(NO. 17)的兩物質。 全面二維層分析系統線性進行檢量線測試，未調制與調制後的積分面 積總量(pA)與體積總量(volume)的系統再現性R2 分別為0.999 及0.997，且兩者相關性0.996。本實驗成功地開發一套簡易型的全面二維氣相層析裝置，可針對空氣中常見VOCs 物質進行全面二維層析之自動化系統，讓分析過程中人性化與普其化。 Comprehensive GCxGC is a chromatographic technique using two different interactions of columns to separate complex compounds in a orthogonal manner. The key component of a comprehensive 2D-GC (GCxGC) system lies in the modulator installed in between the 1-D and 2-D column. Elution segments from the first column are concentrated and injected in series into the second column for orthogonal analysis. Although thermal/cryogenic designations is the most common modulator type in the recent development, it consumes cryogens such as liquid nitrogen (LN2) or liquid carbon dioxide and is costly as a result. In this study, rather than using a thermal/cryogenic modulator, a Deans’ switch-based modulator was used, which was coupled to a homemade thermal desorption unit for analyzing ambient volatile organic compounds (VOCs). The Deans’ switch device generated eluent slices from the first column into the second column. One of the novel features with this method is that rather than using common interaction forces of volatility x polarity for GCxGC, this study used volatility x retention. The first-dimension separation was performed by the difference in volatility (boiling point), the second-dimension separation was performed by the difference in retention force between the analytes and the Al2O3 solid phase on the PLOT column. Instead of using the specialized GCxGC software package, a widely available graphic software (Surfer 8) was adopted for plotting results of GCxGC. This data process method allowed peaks to be easily transformed into contour or 3-D surfaces at a minimal cost. Wrap-around is a common phenomenon seen in GCxGC. It often occurs when peak retention times in the second column are longer than the modulation period, creating ghost peaks on the final contour plot. By simply adjusting modulation periods, wrap-around can be easily detected and then removed. In this study, alkenes over C6 and alkanes over C7 are usually the wrap-around species due to strong retention on the PLOT. Finally, 26 VOC species from C3 to C7, including the co-elution compounds - 2,3-dimethylbutane and 2-methylpentane, were identified by the GCxGC method. The peaks on the contour map could divide into alkane group and alkene group. A calibration curve with sample volumes ranging from 80 to 400 mL was made with an R2 of 0.997 (N=3). The correlation between modulated (GCxGC) and non-modulated (GC) are 0.996. In summary, by combining off-the-shelf components, an automated valve-based comprehensive GCxGC system was constructed with the advantages of rigidity, simplicity, flexibility, and low cost. |
