可控鞘流溶液流速毛細電泳質譜介面於非揮發性緩衝溶液系統靈敏度提升之研究

Abstract

毛細管電泳經常加入非揮發性鹽類於緩衝溶液中以提升分離解析度，當銜接上質譜時，非揮發性鹽類會與分析物競爭電荷，並抑制分析物訊號。鞘流溶液之稀釋雖可降低鹽類濃度，使抑制情形減輕，但同時分析物濃度亦下降。因此本研究開發一可控制鞘流溶液流速之低流速鞘流介面，藉由調控鞘流溶液流速，在稀釋造成鹽類抑制減輕及分析物濃度下降兩因素間，找尋分析物訊號最佳之稀釋比，以提升非揮發性緩衝溶液毛細電泳－質譜的靈敏度。本研究對於ADS微胞及磷酸銨溶液系統之鞘流溶液稀釋比進行探討，在電滲流注入實驗得到使兩溶液系統分析物訊號最佳化之稀釋比，並確認其結果與電泳－質譜實驗相符。另一方面，本研究亦對於相同鞘流溶液稀釋比下，直接注入與電滲流注入訊號差異之原因進行探討，搭配針式幫浦推動鞘流介面注入實驗結果進行比較，證實其主要原因為電滲流注入時，ADS微胞及磷酸根受自身淌度影響其流速較電滲流流速低，使得進入偵測端之濃度低於原本溶液中之濃度。

In CE analysis, nonvolatile buffer is often utilized to enhance resolution. When it hyphenates to mass spectrometer, nonvolatile salt will compete charge against analyte, and suppress the signal of analyte. Diluting the buffer by sheath liquid can lower the salt concentration and alleviate ion suppression, but the analyte is also diluted. In this study, a sheath flow rate-controlled CE/MS interface was developed. By controlling the flow rate of sheath liquid, we found the best dilution ratio of sheath liquid which affects the dilution of salt and analyte to improve the sensitivity of CE/MS using nonvolatile buffer. The dilution ratio of sheath liquid in ADS micelle and ammonium phosphate buffer systems was investigated. We found the dilution ratio that corresponds to the best analyte intensity in EOF infusion experiments, and the results were similar to the real CE/MS experiments. In addition, we studied the factors that cause the difference of analyte intensity between direct infusion and EOF infusion under the same sheath liquid dilute ratio. With the comparison of the experiment of sheath liquid interface infusion by syringe pump, the most influential factor was confirmed. In EOF infusion, the velocities of ADS micelle and phosphate group are lower than the EOF velocity because of their negative charge. Therefore, the concentrations of the solution entering to the MS are lower than the concentration of bulk solution.