| 摘要: | 細懸浮微粒一般為粒徑小於2.5 μm之顆粒物質，稱為PM2.5，組成十分複雜，其有機物質包括烷類、烯類、醛酮類、有機酸、多環芳香族等可佔總質量20-50%，因其化學組成非常多元，需仰賴高分離效果的分析技術，以進一步了解一次污染物(primary pollutants)成分，與形成二次有機氣膠(secondary organic aerosols; SOA)的主要關鍵物質，以及PM2.5對人體健康的影響。全面二維層析(comprehensive GC×GC)分離能力非傳統層析法所能望其項背，已成為新一代層析技術發展的主流。GC×GC 技術是藉由一維管柱與二維管柱的串連，利用兩種以上之靜相作用力來達到正交展開(orthogonality)的分離效果。而GC×GC 之關鍵技術在於一維與二維管柱間之調制器(modulator)的設計與運作，目的在將一維管柱流析出之分析物以脈衝方式壓縮、聚焦後送入第二維管柱進行再一次分離，且由於每一脈衝僅數秒，質譜速度必須夠快，傳統四極柱質譜無法滿足，故使用飛行時間質譜(ToFMS)。本計畫在107年以GCxGC-ToFMS技術結合有機溶劑萃取技術發現板橋地區PM2.5成分中含有明顯的7種塑化劑(Phthalates)與3種有機磷阻燃劑(Phosphorous fire retardants; PFRs)成分，因而發現除食物、接觸途徑進入人體外，污染空氣亦可能是進入人體重要渠道。除溶劑萃取PM2.5濾紙方法外，本研究亦嘗試開發熱脫附氣膠層析技術(Thermal desorption aerosol gas chromatography; TAG)，以便於自動化分析PM2.5上之有機成分，以及有利於實現在線(on-line)分析，了解在特定環境中氣膠形成原因與污染源鑑別，例如交通源成分鑑定、各類工業區的典型排放物質、生質燃燒組成，以及鑑別本地與移入型氣膠在成分上之差異。第二個目標是進一步提升GC×GC的解析能力與降低偵測下限，藉由改進調製方法與一、二維管柱搭配達到此一目的，針對微量但成分複雜的二次氣膠成分，如高度氧化有機物質，以及透過化學衍生法分析高極性含氧有機物，以持續精進二維技術。 ;The composition of PM2.5 aerosols is extremely complex, containing about 20-50% of organic components, including alkanes, alkenes, aromatics, aldehydes, ketones, acids, PAHs, etc. To identify and quantify organic constituents on PM2.5 aerosols, a highly efficient separation technique with superb resolution is required. Comprehensive GC×GC techniques have evolved rapidly into a powerful separation means in the last decade, with superior resolution far beyond conventional chromatography. The basic working principle of GC×GC is to use two columns in-series with different chemical forces to interact with analytes, resulting in orthogonal separation and thus high peak capacity. The most important component in GC×GC is the modulator which connects and also coordinates primary and secondary columns to perform 2D separation. Its role is to periodically enrich and focus effluents from the primary column to form pulsed sample slices which are then sent to the secondary column for further separation. Due to the rather narrow peak width of each sample slice, ToF-MS with much faster data sampling rates than q-MS is utilized to form the system of GC×GC-ToFMS. In 2018, using solvent extraction to combine with GC×GC-ToFMS, we were able to identify 7 phthalates and 3 phosphorous fire retardants (PFRs) from urban (Banqiao district) PM2.5 urban samples. As a result, in addition to the well-known intake channels of oral and skin contact, inhalation of fine particles in polluted air is another channel to pose a health risk. Other than solvent extraction of PM2.5 filter samples, a new technique of thermal desorption aerosol gas chromatography (TAG) is also undergone development in my research group aiming at on-line measurement of PM2.5 in the field to shed light to the formation of secondary organic aerosols (SOA) and source identification. Source markers or profiles of traffic, industrial, biomass burning, and the differentiation of domestic and transboundary PM2.5 events can then be realized. Our second goal is to enhance resolution and sensitivity of GC×GC-ToFMS. By choosing proper column combination and fine-tuning the modulation variables, the improved resolution and sensitivity can facilitate detection of trace level of complex composition of SOA, such as highly oxygenated organic compounds due to prolonged photochemistry. The sensitivity and identification of selective polar compounds can be further elevated through the means of derivatization prior to GC×GC analysis. |
