無接觸式電噴灑游離及大氣壓下化學游離質譜法

Abstract

質譜法是一種能提供待測分析物的質量及化學結構的分析方法。由於質譜分析儀只能用來偵測氣相離子，因此能使凝相態樣品轉換成氣相離子的游離源之開發，在質譜分析中是非常重要的一部分。大氣壓下游離法為一種能在大氣壓下使待測物游離的方法。在大氣壓下游離法中，電噴灑游離法及大氣壓下化學游離法為兩種最重要的游離方法。一般而言，電噴灑游離法中的噴灑頭及大氣壓下化學游離法的游離裝置需要外加高電壓才能使樣品游離。然而，我們的研究團隊在近期已發展出一種不需在電噴灑的噴灑頭及樣品載台上施加高電壓的游離法。本論文的研究主題根據上述的概念，進行新游離源的開發及應用。在論文的第一部分，我們以石墨棒做為輔助電噴灑游離法及大氣壓下化學游離法的基材。在此新的游離法中，極性與非極性的樣品皆能被游離，且此游離法無須在石墨棒上施加高電壓。此外，我們利用石墨棒做為固相微萃取法的探針，並結合石墨棒輔助電噴灑游離法/大氣壓下化學游離法。在論文的第二部分，我們發展出微反應器可與超音波輔助噴灑游離法進行線上分析偵測。在超音波輔助噴灑游離法中，我們以毛細管做為傳輸樣品的通道，毛細管的入口端浸泡在放置在超音波震盪器中的樣品瓶內，而被拉尖的出口端則被放置在質譜儀的進口端。透過毛細現象及超音波震盪的輔助，樣品會經由毛細管進樣端傳輸至出口端。當樣品送至出口端時，析出樣品液會因為受到來自質譜儀所提供的高電廠受到極化誘導效應的影響而產生電噴灑。此外，微流道法對於樣品的前處理及進行微量化學反應非常實用。由於質譜儀擁有很高的靈敏度及與微流道裝置相似的流速，因此質譜非常適合做為微流道法的偵測器。在超音波震盪輔助質譜游離源法之微反應器的實驗，我們選擇了幾種反應速率較快的化學反應，藉此展示此方法能進行線上化學反應的監測。在此方法中，我們將兩支毛細管已各充填兩種液態反應物以一特定角度交叉擺設在靠近質譜進樣端，當反應物從樣品進樣端被輸送至出口端時，由於受到質譜電場影響會進行噴灑混合反應，溶劑揮發後所產生的反應離子可直接由質譜儀偵測。研究結果證明了此超音波震盪輔助質譜游離源法之微反應器，可以進行即時快速化學反應的質譜線上偵測。此外，實驗中也證明此設置在進行線上即時去鹽的效果。

Mass spectrometry (MS) is an analytical tool that can provide molecular weights and structural information for analytes of interest. However, only gas phase ions can be detected. Thus, the ionization technique that can bring samples from condensed phase to gas phase for formation of ions in gas phase play an important role in mass spectrometric analysis. Atmospheric pressure ionization (API) that can be used to ionize analytes at atmospheric pressure have been developed for handling samples in condense phase. The most important API ionization techniques are electrospray ionization (ESI) and atmospheric chemical ionization (APCI). Generally, an ESI emitter and an APCI source have to be applied with a high voltage for initiating ionization to occur. Recently, our research group has demonstrated simple ionization techniques, which do not require any electric contact on the ESI emitter and sample introduction site, so called contactless. On the basis of this “contactless” concept, new ionization techniques and their derived applications are demonstrated in this work. In the first part of the thesis, a graphite rod was used to assist ionization in ESI and APCI. Furthermore, there is no direct electric contact required on the graphite rod. Polar and low-polarity analytes can be ionized using the newly developed ionization techniques. Furthermore, the combination of solid phase micro-extraction with graphite rod-assisted ESI/APCI was also demonstrated. In the second part of the thesis, a micro-reactor on-line hyphenated with another contactless API ionization method, namely ultrasonication-spray ionization (UASI), was explored. In USAI, a capillary inlet is placed to a sample vial subjected into an ultrasonicator, and its tapered capillary is placed close to the MS inlet. There is no direct electric contact applied on the capillary outlet. Owing to capillary action and ultrasonication, sample solution can be directed to the capillary outlet. Electrospray can readily be induced in front of the MS inlet that is applied with a high voltage. Microfluidics is useful for conducting sample pretreatment and micro-reactions. MS is a suitable detection tool for microfluidics owing to its high sensitivity and similar flow rates used in microfluidics. We selected fast chemical-reactions that can be completed within few seconds to demonstrate the feasibility of this UASI-based micro-reactor for on-line monitoring by USAI-MS. Two UASI capillaries that contained different reactants were used to deliver their samples and to fuse the eluents on the cross section in proximity of the MS inlet. The results showed that reaction can be readily conducted using this approach and monitored simultaneously by UASI-MS. In addition, high-salt containing samples can be treated using the current setup to remove salts in situ prior to MS analysis