天然精油廣泛應用於食品、化妝品以及芳香療法等各方面，然而，市售精油的品質良莠不齊，攙混或稀釋之現象時有所聞。本研究利用氣相層析儀搭配火燄離子偵測器（GC-FID)以及質譜儀(GC-MS)，檢測並判讀五十餘件市售樣品之圖譜，配合文獻考證，並對照本實驗室建立之精油指紋圖譜資料庫，檢出數樣異常的精油樣品，分別爲：精油中添加揮發性有機溶劑-毒管物質ニ氯甲烷（dichloromethane);添加塑化劑鄰苯ニ甲酸酿類（Diethyl Phthalate, DEP);添加多元醇類等不當稀釋。透過本研究的兩種精油分析技術，可以快速、有效地檢測精油樣品是否純正，進而維護使用者的健康與安全。

The natural essential oils have been vastly aoolied to numerous areas such as foods, cosmetics, and aromatherapy in recent decades. However, the quality of the commercially available essential oils varies to a great extent due to adulteration and dilution. We have investigated more than fifty samples of commercially available essential oils by analytical instruments such as gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectroscopy (GC-MS) in this study. By comparison with reported literature data and the spectroscopic data bank established in our laboratory, several adulterated samples have been detected. The improper practices discovered were: Adulteration with volatile organic solvents such as the toxic dichloromethane; Dilution with plasticizers, such as diethyl phthalate (DEP), and polyols. With the technologies established in this study by GC-FID and GC-MS, the purity and the quality of the essential oils can be effectively and efficiently authenticated; and thus the health and the safety of the consumers can be ensured.