| 摘要: | 含氧揮發性有機物質 ( oxygenated volatile organic compounds; OVOCs )為光化學反應過程的中間產物，且大量出現於工業製程中。因其反應性、極性較高，故製作標準氣體時通常不採取高壓鋼瓶靜態配製法，因不利於長久保存，而採動態產生方式為較佳之策略。因此本研究以自製滲透管的方式動態製備OVOC標準氣體，可產生不同濃度下的多物質混合標準氣體。 本研究以動態滲透管法製備OVOC標準氣體，物種包括：醇、醚、醛、酮、酯類，同時加入不含氧之非極性物質：苯、甲苯、乙苯及鄰-二甲苯，作為OVOC濃度推估之內標物。分析方法是以線上熱脫附法搭配GC/FID ( gas chromatography/flame ionization detector ) 對滲透法進行評估，針對13種OVOC物質如：異丙醇 ( isopropanol )、正丁醇 ( n-butanol )、丙二醇甲醚 ( propylene glycol mono-methyl ether )、甲醛 ( formaldehyde )、乙醛 ( acetaldehyde )、丙醛 ( propanal )、丙烯醛 ( acrolein )、丙酮 ( acetone )、丁酮 ( methyl ethyl ketone )、甲基異丁酮 ( methyl isobutyl ketone )、乙酸乙酯 ( ethyl acetate )、乙酸丁酯 ( butyl acetate ) 與丙二醇甲醚醋酸酯 ( propylene glycol mono-methyl ether acetate )，其線性之R2值皆在0.99以上，相對標準偏差 ( RSD ) 皆在2 %內，驗證自製滲透管具有高穩定濃度輸出的功能。滲透管濃度推估是以FID對各物種之單位碳感度的概念進行換算，以注射純物質推得各物種之單位碳感度，進而以莫耳數比估算滲透管之輸出濃度。 隨著自製滲透管物種數量的增加，單管柱無法有效分離各物種，因此再以實驗室自行開發之全面二維氣相層析技術 ( Comprehensive GC x GC ) 將繁雜的物種進行更有效的分離。日後可將成功開發完成地自製滲透管OVOC技術實際應用於野外極性物質的自動監測上。 Oxygenated volatile organic compounds ( OVOCs ) are originated from biogenic and anthropogenic sources, as well as from photochemical reactions of volatile organic compounds (VOCs). The high reactivity and lability of OVOCs makes preparation of diluted mixture and storage in high-pressure cylinders unstable. Thus, it is preferred using the dynamic dilution method to the static dilution method and cylinder storage. As the result, this study presents the dynamic dilution method of preparation of OVOC standards to produce gas mixture standards with any chosen composition and at any desired concentration level. In this study, self-made permeation tubes, including alcohols, ethers, aldehydes, ketones, esters, were selected as our OVOCs sources. To verify the applicability of permeation tubes, a self-made preconcentration system and GC/FID were used as the assessment tool throughout the study. Thirteen OVOCs, i.e., isopropanol, n-butanol, propylene glycol mono-methyl ether, formaldehyde, acetaldehyde, propanal, acrolein, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate and propylene glycol mono-methyl ether acetate were prepared as permeation tubes to generate continuous flow of gas mixture at ppbv level. Repeated analyses by GC/FID showed RSD less than 2% and R2 better than 0.99, verifying the stable output of the method. A few non-oxygenated VOCs such as benzene, toluene, ethylbenzene and o-xylene were also included in the mixture to serve as surrogates for estimating dilution factors based on flame ionization detection (FID). As the number of added compounds increased in the mixture, single column GC became difficult to meet our demands for complete separation. As a result, the two-dimensional technique was adopted for greater separation efficiency. The use of the comprehensive GCxGC technique was able to successfully separate the mixture. Ultimately, this technique of OVOC permeation method will be applied to field measurements for on-site automated calibration and quality-control of ambient OVOC monitoring. |
