| 摘要: | 全面二維氣相層析技術（comprehensive two-dimensional gas chromatography; GC × GC）擁有一般傳統層析技術所無法達到的高峰容量特性，大幅改善了在分離高度複雜樣品（例如油品、香精）時容易發生的共析（co-elution）問題，因此使得GC × GC成為新一代層析技術之主流。
GC × GC一旦聯結質譜偵測器便成為極強大的定性、定量工具，其中又以聯結飛行時間質譜儀（time-of-flight mass spectrometer; TOFMS）為目前商品化設備的主流，因TOFMS具有高資料擷取頻率（200Hz）與高質量解析的能力，自然成為與GC × GC的最佳匹配，對未知物鑑定能力遠高於其他非質譜偵測器（例如：火焰離子偵測器flame ionization detector; FID），因此在分離與鑑定能力上展現出前所未有的優勢。然而商品化的GC × GC - TOFMS造價昂貴與維護不易，無法普及於一般實驗室，因此本研究嘗試利用一般實驗室既有的GC改裝成具有GC × GC功能的設備；使用丁式切換器（Deans switch）作為閥件型調制器（valve-based modulator），並在層析尾端連接FID與四極柱質譜儀（quadrupole mass spectrometer; qMS）而成為一GC × GC – FID/qMS系統。雖然qMS的數據擷取頻率低，會使調制峰失真，故無法作為準確定量之偵測方式，但有限之訊號擷取點仍具有定性之功能，而完整的GC × GC圖譜則交由FID完成，作為定量之訊號來源。
本研究建立之GC × GC - FID/qMS系統，以DB-1作為第一維管柱，DB-1701作為第二維管柱，展現分散力（dispersive force）與極性（polarity）偶合作用下之正交效果，並使用自行配製含有34種化學成份（包含烷、醇、酯和酮）的混合標準品以測試分析系統之定性、定量效能。在定性工作上qMS可得到部份相應的物質資訊；在定量上透過FID則可得到良好的再現性與線性結果，RSD可達0.89%以上，而5種烷類標準品之R2可達0.98以上。在研究中亦嘗試以本方法對生活中常見之酒品及油品進行分析，建立樣品之特性指紋圖譜。
;Comprehensive two-dimensional chromatography (GC × GC) is inherited with high peak capacity that dramatically improves separation resolution and alleviates the co-elution problem for complex samples (such as fuels or essential oils), making GC × GC a main stream technique in modern chromatography.
When coupling with mass spectrometry it becomes a powerful qualitative and quantitative tool, particularly if time-of-flight mass spectrometry (TOFMS) is chosen due to its fast data acquisition rate (200Hz) and high mass resolution, making the GC × GC – TOFMS technique superior to other GC detection methods (e.g., flame ionization detection; FID). However, because of the high cost in purchase and maintenance, GC × GC – TOFMS is generally out of reach for average budget-concerned laboratories. As a result, this research is attempted to transform a regular GC into a GC × GC setup using a Deans switch as the valve-based modulator and both FID and quadrupole mass spectrometry for detection (GC × GC – FID/qMS). Although the data acquisition rate for qMS is too low for normal GC × GC use, its role in this study is only limited to structural identification, whereas quantitation is performed by FID to acquire the complete GC × GC contour.
Our GC × GC - FID/qMS system used a DB-1 column (60 m × 0.25 mm i.d. × 1 μm d.f.) as the first dimensional (1D) column and a DB-1701 column (1 m × 0.25 mm i.d. × 0.5 μm d.f.) as the second dimensional (2D) column to reveal the orthogonality of zero-polarity vs. mid-polarity. By searching with the NIST (version 08) library, 7 compounds out of 34 in the standard mixture, including alkanes, alcohols, esters, and ketones, were able to be identified. Quality assurance of linearity and precision were performed for the target compounds. For instance, the five alkanes, i.e., n-octane, n-nonane, n-decane, n-undecane, and n-dodecane, showed linearity (R2) better than 0.98 in the concentration range of 10 - 100 ppm and the relative standard deviations (RSDs) better than 0.89% (n = 5). With this newly developed GC × GC - FID/qMS method, the fingerprints of liquor and gasoline samples were successfully obtained. |
