一體式單槽介面於低電滲流毛細電泳質譜之研究暨應用

Abstract

使用無鞘流介面進行毛細電泳/質譜分析時，並無鞘流溶液的補充，因此須將毛細電泳操作在高電滲流的環境下，才能維持穩定之電噴灑。當緩衝溶液系統所提供的電滲流過低時，則以低稀釋效應又可補充流速的低流速鞘流介面較為適用。實驗室先前曾發展具無鞘流與低鞘流雙模式的一體式單槽介面，本研究將針對此介面於低鞘流模式中，溶液補充對分析物訊號影響的探討，最後將此介面應用於牛奶中乙型受體素之分析。

由於毛細電泳操作在酸性條件下，其電滲流的速度相當低，需要補充溶液來協助電噴灑法之穩定，而補充溶液多寡會影響稀釋效應，進而影響質譜分析時的靈敏度。此外，若噴灑時的流速很低，則實驗將操作在質量靈敏區域，流速會對訊號產生影響，因此影響訊號強度的因素就不只有稀釋效應，質量靈敏效應也會造成影響。本研究首先對在低電滲流環境下鞘流及無鞘流模式的分離效果進行評估，發現在無鞘流式下分離解析度會變差。接著探討稀釋效應與質量靈敏效應對訊號的影響，找到訊號最佳時的噴灑電壓。最後搭配固相萃取進行樣品前處理，在最佳噴灑電壓下，將此介面應用於牛奶中七種乙型受體素之分析，以SRM模式偵測並找到此方法之偵測極限。

When sheathless interface was employed in CE/MS, EOF must be high enough to stabilize the electrospray process. A common choice for interfacing CE to MS in low EOF condition is the low-sheath flow interface, providing stable electrospray with low dilution effect. Recently a dual mode CE/MS interface had been developed in our group. In this research, the effect of make-up flow on the signal intensity using sheath liquid mode was investigated. In addition, the interface was applied to analyze β-agonists in milk. Because the EOF is often low in acidic BGE, the make-up flow is needed to maintain the stability of electrospray. The make-up flow rate affects not only the dilution effect but also the mass sensitive effect. If the flow rate of electrospray is very low, the ESI will operate in mass sensitive region so the signal intensity would be affected by the flow rate. First part of this work was to evaluate the separation efficiency with sheath liquid and sheathless mode in low EOF system. The resolution of sheathless mode was found to be poorer than sheath mode. Second part of this work studied the dilution effect and mass sensitive effect to find the optimum spray voltage. The optimized conditions in combination with Solid-phase extraction was used to analyze seven β-agonists in milk. The limit of detection (LOD) of this method (SRM) was found in the range of 10-100ppb.