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  • 學位論文

非連續電噴灑及晶片式微注射器於毛細管電泳-質譜與毛細管電層析-質譜之開發與應用

The development of CE-MS and CEC-MS interfaces based on noncontinuous electrospray and chip-based microinjector

指導教授 : 何國榮

摘要


利用非連續性電噴灑法,解決在無鞘流電泳質譜界面中所遭遇的電灑噴頭堵塞問題進而利用非連續性電噴灑的特性而發展出多通道低流速鞘流毛細管電泳質譜界面。另外,也利用短的毛細管電層析管柱銜接至晶片式微注射器以達到快速分析之目的。 在較靈敏的無鞘流毛細管電泳界面中,由於毛細管電泳的電滲流流速約為50~250 nL/min,電噴灑頭之口徑通常需被拉尖到~ 20 µm以下以符合理想噴灑流速。然而對於一個拉尖的噴頭而言,在塗佈導電層到噴頭時容易出現噴頭的損毀以及在分析進行時造成噴頭的堵塞。為了解決上述因為噴頭口經縮小所導致的問題,使用與分離管內徑ㄧ樣的噴頭口徑做電噴灑,再利用非連續性的電噴灑法以有效的增加噴灑流速到最佳流速。在20 Hz,20 %工作週期下可以得到較強且穩定的訊號。離子阱的最大離子進樣時間設定為10 ms,以避免離子儲存的平均效應。從實驗結果得知,使用50 µm口徑的噴灑頭時,在150 nL/min的操作流速下,非連續性電噴灑法可得到比連續性噴灑訊號更強且穩定的訊號。 為了有效提升毛細管電泳質譜的通量分析,開發出多通道低流速鞘流毛細管電泳質譜界面。由於低流速鞘流界面有較小的樣品稀釋比例且可產生較小的電噴灑液珠, 因此它有著比一般商業化電噴灑界面更靈敏以及更抗鹽的特性。然而由於低流速鞘流界面的噴灑流速較小,因此噴灑頭需很靠近質譜進樣端,使得原先在多通道毛細管界面中的金屬旋轉盤無法放置其中。為了使低流速鞘流界面可被應用在多通道毛細管電泳質譜,我們利用非連續電噴灑的概念,使此四根毛細管電泳產生序列式噴灑,再與質譜儀同步化。由於此四根樣品訊號可以不互相干擾並被分別呈現,因此成功的開發出多通道低流速鞘流毛細管電泳質譜界面。 為了使毛細管電層析質譜達到快速且自動化的分析,利用短的填充式毛細管電層析管柱銜接上晶片式微注射器以取代一般的整合式晶片毛細管電層析質譜。因為微注射器可產生較小的樣品帶寬,且可自動化,以及短管柱上的快速分析,因此,此裝置不僅可以保留微流體晶片分析的優點更可以避免在晶片內填充靜相顆粒的困難。 此外,也開發了晶片式微注射器的流體動力進樣方法,使其有著更穩定且快速的樣品進樣。在壓力進樣下,因為受限於填充式分離管柱的背壓,樣品只會流向進樣通道與樣品廢液通道,因此可以在晶片注射器上製備短的進樣通道以形成特定的進樣帶寬。並利用針筒式幫浦以及ㄧ個六向閥,使得樣品可在微注射器上做流動注入。如此,不僅可提供較穩定的注射方法,並可以針對大量樣品做快速注入分析,且已成功的應用在蛋白質水解片段上的序列分析。

並列摘要


Several approaches based on noncontinuous spray and chip-based microinjector have been developed to overcome the clogging problem in sheathless CE-MS, and to increase the throughput in CE and CEC-MS. To develop a more practical and sensitive CE-MS interface, a sheathless pulsed–ESI interface has been developed for coupling capillary electrophoresis (CE) with ion trap mass spectrometer (MS). In sheathless CE-MS, because the EOF in CE is about 50~250 nL/min, in order to meet the optimal flow rate of the sprayer, the orifice of the sprayer has to be tapered down to ~20 µm or less o.d. Nevertheless, the susceptibility of breaking or clogging of the tip during coating or sample analysis limits the application of the tapered tips having small orifices. The use of noncontinuous spray mode allows the use of a sprayer with a larger orifice thus alleviate the problem of column clogging during conductive coating and CE analysis. A pulsed ESI source operated at 20 Hz and 20% duty cycle was found to produce the optimal signals. For better signals, the maximum ion injection time in the ion-trap mass spectrometer has to be set to a value close to the actual spraying time (10 ms). Using a sprayer with 50 µm o.d., more stable and enhanced signals were obtained in comparison with continuous CE-ESI-MS under the same flow rate (150 nL/min). The utility of this design is demonstrated with the analysis of synthetic drugs by capillary electrophoresis-mass spectrometry (CE-MS). For increase the throughput in CE-MS, a multiplex electrophoresis–mass spectrometry using four low flow sheath liquid ESI sprayers has been developed. Because of low sample dilution and the producing of smaller droplets, low flow interface is known to outperform conventional sheath liquid interface in sensitivity and the tolerance of salts. In a low flow interface, the sprayer is very close to the MS entrance for better ion transmission and because of the limited space between the sprayer and the entrance aperture of the ESI source, multiplex can not be achieved with the conventional rotating plate approaches. Based on noncontinuous spray for each sprayer, the multiplex low flow system was achieved by applying ESI potential sequentially to the four low flow sprayers, resulting in only one sprayer being sprayed at any given time. The synchronization of the scan event and the voltage relays was accomplished by using the data acquisition signal from the ion trap mass spectrometer. By synchronization, the ESI voltage was provided to the sprayers sequentially according to the corresponding scan event. With this design, a four-fold increase in analytical throughput was achieved. To perform fast analysis in CEC-MS approach, an approach to perform chip-based packed CEC-MS was proposed. This fast CEC-MS approach was based on a chip-based microinjector and a short fritless CEC column. Unlike integrated CEC chip, a chip-based poly-(dimethylsiloxane) (PDMS) microinjector was incorporated with a short fritless packed CEC column. By taking the advantages of small sample plug produced in channel cross intersection, automation in sample injection and separation, and fast separation because of a short CEC column, the proposed approach not only preserved the merits of chip analysis (fast separation and automation) but avoid the difficulty in packing ODS particles inside a chip. For better ESI sensitivity, this device was coupled with MS using a low flow sheath liquid interface. The potential and limitation of this device were evaluated in the analysis of a peptide mixture. To develop a more reliable sample loading method and to increase the throughput in sampling, a flow injection sampling method has been implemented for fast CEC-MS analysis. Because of the high back pressure of the CEC column, sample from the syringe pump will flow only into the sampling and waste channel. Therefore, a sample plug was formed according to the length of the sampling channel. With the incorporation of a six-port valve and a syringe pump to the chip microinjector, sample was delivered to the sampling channel at a flow rate of 1.56 µL/min. This simple and semi-automation system allows rapid sampling and high sample throughput. The potential and limitations were demonstrated in the analysis of peptides and protein digestion.

參考文獻


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