同步離子配對萃取及即時線上衍生氣相層析質譜技術應用於茭白內生吲哚乙酸之分析

Analysis of Indole-4-ActicAcid in Zizania latifolia by Single Step Ion Pair Extraction/on-Line Derivatization and Gas Chromatography-Mass Spectrometry

This work presents an improved GC-MS method to analyze indole-3-aceticacid, the endogenous auxin in plant samples. Zizania latifolia plant tissues were used to evaluate this method. The method involves extraction of＜1g samples by grinding the plant tissue in liquid nitrogen followed by an extraction cocktail including buffer, tetrabutylammonium ion pair/derivatizing agent and small amount organic solvent. The extracted organic solvent was subject to GC-MS analysis without further purification. The on-line derivatization takes place in the injection port of GC equipped with a standard split/splitless injection port; and 2μL of organic extract containing the IAA-tetrabutyl-ammonium salts was injected. The analytes were then identified and quantitated by 70 eV electron impact quadrupole GC-MS. The standard split/splitless injection-port derivatization technique provides fast and reproducible results for IAA analysis with moderate sensitivity. The detection limit is 5 ng IAA per injection in scan mode and 500pg IAA per injection for 2 ions of selected ion monitoring mode. The free IAA concentration of the edible gall of Z. latifolia ranged from 0.26 to 2.43μg/g fresh weight, and the IAA concentration of hydrolyzed samples ranged from 1.55 to 6.34μg/g fresh weight. The butyl ester of indole3aceticacid has an extended retention time on the polar DB-waxGC column, and the expanded molecular ion m/z=231 enabled IAA butyl ester to be separated from other potential contaminations that were present in the plant extracts. Extraction recovery of the IAA in spiked plant samples was 73.9% with RSD=10.8%. 本研究針對植物內生生長素吲哚乙酸之分析發展出一改良氣相層析質譜方法，並以茭白（Zizania latifolia）為方法驗證材料。本方法使用小於1g的植物材料，以液態氮浴在研缽中研碎，並加入包含緩衝液、四丁基季氨鹽離子配對／衍生劑及有機溶劑萃取溶液。此有機溶劑萃取溶液不需更進一步的純化，可直接進行氣相層析質譜分析。將2μL包含吲哚乙酸四丁基季氨鹽之萃取液注入氣相層析質譜儀進樣口，在250℃下進行即時線上衍生產生吲哚乙酸丁酯，再經70eV電子轟擊式四極柱氣相層析質譜儀定性與定量。此標準注射口線上衍生吲哚乙酸丁酯的方法，提供一個簡便快速及具有可接受靈敏度的氣相層析質譜儀定性與定量分析方式。全質譜掃瞄方式的偵測極限約為每次注射吲哚乙酸5ng，選擇離子監測（二離子）模式之偵測極限約每次注射吲哚乙酸0.5ng。茭白筍部的游離態吲哚乙酸約在1.55到6.34μg／gF.W.，結合態吲哚乙酸約在1,540到8,340ng／gF.W.。吲哚乙酸丁酯的質量數離子（m／z=231）在極性的DB-Wax分離管柱中有較長的滯留時間，此較長之滯留時間亦有助於與植物中潛在的干擾物質分離。本方法的總回收率約為73.9%，相對誤差約為10.8%。