本研究的目的以逆相層析系統來定量分析食用油中飽和及順、反未飽 和脂肪酸,在此研究進行的方法有兩種:1.在動相溶劑中添加銀離子,來 達到選擇性的沖提,2.使用最適化的溫度、溶劑的組成和梯度方式來達到 分離結果。 在動相中添加銀離子主要的目的是銀離子會與 未飽和脂肪酸的雙鍵形成錯合物, 所以可以利用此關係來達到分離 順、反未飽和脂肪酸。因為順式能與銀離子形成強 錯合物,而反式 與銀離子會形成弱的錯合物,這是由於立體障礙的影響,所以利用 此關係順/反式容易達到分離。結果顯示銀離子濃度越高對於順、反未飽 和脂肪酸 的分離越好,但是高濃度銀離子容易形成沈澱對管柱靜相 造成傷害,而使管柱壽命減短 ,解析度降低。不添加銀離子,在適當的 條件掌控下C18管柱亦可被用來進行食用油中脂肪酸的分析,本實驗使 用coumarin進行脂肪酸的衍生化,配合螢光偵測器在波長325NM 偵測以提高靈敏度,並且由相關的Van Holf方程式探討溫度滯留 的影響,結果顯示降低溫度的結果可以有更好的解析度產生,但是分析時 間會拖長。此外,經由溶解度參數理論討論有機溶劑組成的影響,並作一 個系統性和合理化的探討。結果顯示有機溶劑組成降低時分離效果亦明顯 提高,由於動相極性增加的關係。然而,事實上分析時間亦同樣的拖長。 為了達到分離快速的目的利用三種有機溶劑氰甲烷、甲醇和水混合在55 ℃下分離,結果顯示11個飽和和順、反未飽和脂肪酸能夠在40分鐘內 快速的分離。本方法的發展可應用於食用油的分析上,接著對油樣品經皂 化萃取和衍生化,並以HPLC進行分析,每一對脂肪酸可經由層析標準 品溶質比對後可被確認。接著以C17:0 為內標物來作定量分析的測 定。並以添加C17:0三酸甘油脂進入到混合油樣品中,反應後作回收 率的計算所測得結果為90%。在偵測極限測定上,測得結果為< 1p pm 而S/N=3。而在研究的六種油樣品之中,以油酥含有高百分比 的trans脂肪酸(14.5%)。 The goal of this research is toquantitatively analyze the satu rated and cis/trans unsaturated f atty acids in dietary oils by Re versedPhase Liquid Chromatograph y (RPLC).There are two methods t o process the research: 1.Use of silver ion in the mobile phase for the selective elution. 2. Us e of the optimized temperature, solvent composition and gradient program to achieve the separati on. The main purpose to add s ilver ion in mobile phase is to form the silver complex with the double bonds of unsaturated fat ty acids. Because the trans conf ormation will form a weaker comp lex than the cis conformation du e to the steric hindrance, the s eparation between cis and trans conformation can be readily achi eved. The result shows that the use of higher concentrations of hence, silver ions provides a be tter separation, but is likely t o cause the precipitation and re duce the lifetime of the column. Under proper controls, the C18 column can be used to pr oceed theanalysis of fatty acids without theuse of silver ions. The research makes use of coumari n to proceed the fluorescence de rivitization in order to increas e the sensitivity. The effect of temperature on retention is inv estigated and correlated to Van Holf equation. Results show that the decrease of temperature wou ld increase the resolution but a longer analysis time is require d. Moreover, the effect of organ ic solvent composition on the re tention was also systematically e xamined and rationalized by the theory of solubility parameter. Results show that when the compo sition of organic solvent is red uced, the separation is obviousl y improved due to the increase o f the mobile phase polarity. How ever, the analysis time is subst antially increased as well. To a ttain a quick separation, a tern ary system composed of acetonitr ile, methanol and water were pro grammed for the separation at 55 ℃. The result reveals that 1 1 saturated and cis/trans unsatu rated fatty acids can be readily separated in 40 minutes. The developed method was applied for the analysis of dietary oils . After the soapnificative extra ction and derivitization, HPLC a nalysis was proceeded and each f atty acid was identified by the comparison of retention times wi th those of the standard solutes . Quantitation was performed wit h the use of C17:0 as the intern al standard. By spiking C17:0 tr iglyceride into the mixed oils, the recovery of was calculated to be 90%. The detection limit was determined to be <1ppm with a S/ N=3. Among six oil samples inves tigated, the butter contains the highest percentage (14.5%) of t rans fatty acid.
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