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    题名: 以毛細管電泳法分離位置及對掌異構物之方法開法與應用;Application of caplillary electrophoresis to separate positional isomers and enantiomers
    作者: 蕭榮憶;Jung-Yi Hsiao
    贡献者: 化學研究所
    关键词: 熱力學參數;位置異構物;主-客錯合物;結合常數;環糊精;毛細管電泳;除草劑;鹽析;對掌異構物;氯化苯氧基酸;chlorophenoxy aicds;enantiomers;apparent binding constants;host-guest complex;naphthalenesulfonates;positional isomers;thermodynamic parameters;salting-out;herbicides;capillary electrophoresis;cyclodextrins
    日期: 2006-06-08
    上传时间: 2009-09-22 10:16:11 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 異構物(isomers)係指擁有相同分子式之不同化合物,其中取代基排列位置不同者稱為位置異構物(positional isomer),互為鏡像但不可重疊的立體異構物則為對掌異構物(enantiomer)。此二種異構物之間因分子量及帶電量相近或相同,無法利用毛細管區帶電泳法分離。本研究在緩衝溶液內添加對掌選擇劑(chiral selector),使其與分析物錯合形成主客錯合物,產生視電泳遷移率之差異而達到分離之效果。 本研究的主要目標之ㄧ為利用毛細管電泳法分離?磺酸鹽位置異構物,並探討其與環糊精之間的作用關係,進而計算其結合常數與熱力學參數,以了解其分離機制。經由視電泳遷移率與對掌選擇劑(β-CD)濃度之關係,以非線性方程式及三種線性方程式所估算出之結合常數與文獻值比較,證實毛細管電泳法確為一便利且準確之結合常數計算方法。在資料數充分之條件下,四種估算結合常數之方程式中以非線性方程式所得之結果最為準確。實驗結果並顯示位置異構物取代基之種類、位置及數量會對錯合行為造成影響,當β位置上接有取代基時因立體障礙較小,結合常數較大,若取代基在α位置上則反之。此外,藉由不同溫度下結合常數之變化,可計算出主-客分子錯合作用時之熱力學參數變化。經由實驗結果得知?磺酸鹽與β-CD之錯合作用為自發性反應,且在溫度越低時趨勢越強。 本研究的第二目標即在建立一套方法,利用毛細管電泳法分離並檢測在水環境中的氯化苯氧基酸對掌異構物,並搭配前處理步驟以達到濃縮及去除基質干擾的目的。結果顯示,使用添加15 mM HP-β-CD的50 mM醋酸鹽緩衝溶液,施加25 kV的正向電壓所得到之分離效果最好。 一般毛細管電泳儀最常撘配UV偵檢器,其偵測極限都較高。因此,在真實水環境樣品的檢測上都須經過濃縮的步驟,以增加樣品的濃度。本研究所採用的萃取方法為固相萃取法,經由此方法可將樣品濃縮至少2000倍以上,並可去除部份基質干擾。但毛細管電泳法受離子的干擾影響很大,因此在進樣前必須增加一去鹽的步驟─鹽析,再次降低基質干擾。本研究所使用的鹽析條件為2 mL的水樣添加0.45 g NaOH,以1 mL的ACN進行萃取。經由搭配Oasis? HLB固相萃取管柱及鹽析的方法,當針對含有2.5 μg/L分析物之100 mL水樣進行回收率的探討,在最佳條件下各分析物之回收率均高於68%,相對標準偏差在13%以下,顯示本方法具有良好的回收率與再現性。 Capillary electrophoresis (CE) is one of the most popular analytical techniques in separation of positional/structural isomers and chiral compounds, and also can be used to evaluate the binding constants and thermodynamic parameters of guest-host inclusion complex. The first part of this study is application of CE to simultaneously determine the apparent binding constants and thermodynamic parameters for six positional/structural naphthalene sulfonate derivatives with ?-cyclo- dextrin (?-CD). The change in electrophoretic mobilities were used to assess the binding constants by nonlinear regression and three different linear plots methods (named double reciprocal, x-reciprocal and y- reciprocal). The substituent group(s) attached to the naphthalene ring considerably affected the inclusion behaviors of these naphthalene sulfonate derivatives. The binding constant varies over almost one order of magnitude and a highly selective sequence is obtained between these guest model compounds. Naphthalenesulfonates with the substituent(s) at the 2-position(s) displayed stronger interaction with ?-CD, and gave well compatible results by these four plot methods. While at least one substituent was substituted into the 1-position of naphthalene showed the weak interaction or no interaction with ?-CD. Comparison to three linear regression methods, the non-linear regression method proves to be the most suitable for these determinations. Additionally, apparent binding constants for each structural isomer with ?-CD at several temperature, and thermodynamic parameters for binding were also calculated and discussed. The second part of this study is application of CE to separate two groups of chiral chlorinated pesticides (dichloroprop and mecoprop) in water samples with (2-hydroxypropyl)-?-cyclodextrin (HP-?-CD). The most effective separation conditions were to use 50 mM ammonium acetate with 15 mM HP-?-CD at pH 4.6. Determination of the apparent binding constants and thermodynamic parameters for these two chiral pesticides were also calculated. The use of solid-phase extraction (SPE) and salting-out effect for the off-line preconcentration of chiral pesticides is demonstrated in this study. Oasis HLB-SPE cartridge was used to reduce interferences and enhance the extraction of analytes from surface water samples. The most effective salting-out effect was 0.45 g NaOH and 1.0 mL acetonitrile in 2-mL of SPE extract. Significantly sensitive improvement was observed and more than 2000-fold enrichment was achieved. Recovery of the analytes in various spiked water samples was up to 68% with RSD less than 13%.
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