瞬間釋壓法於超臨界流體萃取水溶液之研究

Abstract

在本實驗室自製的超臨界流體萃取系統中, 以較大內徑的的不□鋼管 ( ID=178um ) 取代一般使用的限流器 ( ID=25um ),對以二氧化碳超臨界流 體萃取溶解在水中的酚 (Phenol),進行無溶劑的分析物收集 ;發現實驗中 並沒有限流器被阻塞的問題, 並且對酚在 200atm, 50 ℃萃取時, 有不錯 的收集率 96％. 但是發現收集率並沒有很好的再現性;此外我們也針對靜 態式萃取, 動靜態混合式萃取, 及動態式萃取等方法進行水樣品沖出的探 討; 由於銅離子在二氧化碳超臨界流體中的溶解度極為微量,因此可以利 用銅離子作為水樣品沖出的指標.在相同的萃取條件下,對銅離子水溶液萃 取, 發現沖出量並不規則,而與酚的水溶液萃取 的情形相似.我們認為避 免水溶液樣品在萃取中發生沖出的現象應可從下述兩點著手: 1. 減少萃 取槽中二氧化碳傳送管件的內徑. 2. 加裝一個相分離裝置, 以分離沖出 的水樣品. Supercritical Fluid Extraction (SFE) technique has aroused great attention in solid sample preparation. Recently, researchs of extraction directly from liquid (aqueous) matrix also gain a lot of momentum. During the sample recovery using SFE, it occurs frequently that the restrictor is plugging due to the coolingcaused by the rapid expansion of the fluid. It greatly influences the extraction efficiency and the analytical precision. A system is developed in this laboratory to extract analytes from liquid matrix using a large bore tube to replace a regular small bore (∼25um) rstrictor. Supercritical CO2 is introduced to the samplecell for static extraction. The fluid is then released to acollection tube through a metering valve and the large bore tube. Phenol aqueous samples are examined. No plugging phenomenon has been observed in this solventless collection technique. Under 200atm and 50℃, the recovery of phenol is 96％. However, the reproducibility is poor. It may be correlated to the carry-out of the sample during the rapid depressurization after extraction. In addition, dynamic extraction method is investigated for comparison. Occasionally, water(non-solvated) is observed to be carried out by CO2. Suggestions are made to avoid liquid carry-out and to improved thw operational precision of this staticxtraction system.