CE/FT-IR 金属雾化器接口*


何林涛    James A. de Haseth

Department of Chemistry, University of Georgia, Athens, GA30602-2556, USA



        毛细管电泳(CE)可以说是“电驱动”的色谱, 是色谱家族中较新的一员,跟其它色谱技术如GCHPLC SFC相比,CE常被称之为分析速度快,样品用量少,应用范围广的高效分离技术。

         色谱与付里叶红外(FT-IR)光谱的联用是重要的分析工具,GC/FT-IRSFC/FT-IR联用技术已有广泛的研究,并有大量的文章发表,目前正在走向商品化,离机联用Off-Line HPLC/FT-IR已有商品接口仪器。但是,CE/FT-IR至今未有报导。本文研究CE/FT-IR联用接口,并证明CE/FT-IR的联用是可行的。

         HPLC/FT-IR有效的接口是采用溶剂消除法实现的,CE/FT-IR的联用要比其它色谱技术与FT-IR的联用困难得多。基于溶剂消除法的CE/FT-IR联用有三个主要困难:(1) 正常的CE操作中必需的电接触(electric contact)而产生高压,(2) CE所必用的缓冲剂对IR检测的干扰,(3) 为达到IR检测的灵敏度,必须要形成非常小的样品沉积点。

         根据上述因素的考虑,我们已成功地设计了以金属雾化器为主要组件的CE/FT-IR接口,并选用挥发性的缓冲溶液醋酸铵作CE电解液,成功地得到一些样品的CE/FT-IR光谱。图1为我们修改了常规CE毛细管柱子,将之延长而供 CE/UV/FT-IR用的新柱子。图2 CE/FT-IR金属雾化器接口的示意图。在大部分情况下,当使用挥发性缓冲溶液,几乎不需要对缓冲溶液作差谱处理,而样品的沉积尺寸大约200mm。图3 显示了以醋酸铵作CE电解液所得到的CE/FT-IR光谱和其差谱结果比较。金属雾化器CE/FT-IR接口有希望应用于定量分析,CE的馏分制备,以及对CE机理与理论的研究。


FIGURE 1. CE/UV/FT-IR column and the modified high                      FIGURE 2. Metal nebulizer CE/FT-IR interface. 

voltage supply. Capillary: 75m i.d., total column length:                       The negative polarity of the high voltage supply

110 cm, 50 cm between start and UV detector.                                      is connected to the metal nebulizer.




Figure 3.  CE/FT-IR condition: 0.01M N-Acetyl-D-glucosamine (GlcNAc), Pressure injection 10 seconds, 15 KV voltage, 75 mm i.d. 80 cm long home-made CE/UV/FT-IR fused silica capillary column, 20 psi helium for nebulization. FT-IR spectra were collected on Perkin-Elmer 2000 with microscope at resolution of 4 cm-1 and 64 scans. 







Metal Nebulizer CE/FT-IR Interface*


Lin-Tao HE and James A. de Haseth

Department of Chemistry, University of Georgia, Athens, GA 30602-2556, USA


   Capillary Electrophoresis (CE) is an electricity-driven chromatography. Compared with other chromatographic technologies such as GC, HPLC and SFC, CE can be broadly described as high-efficiency separations with high analysis speed, low sample volumes and wide applicability to polar and non-polar substances.

   An interface between chromatography and FT-IR is an important analytical tool. GC/FT-IR has been commercially available for  two decades. HPLC/FT-IR and SFC/FT-IR have been researched in a large number of publications and interfaces are presently being commercialized. CE/FT-IR, however, has not been reported previously. In this work, CE/FT-IR was investigated and proven feasible in our laboratory.

   CE/FT-IR is more difficult than other chromatography/FT-IR techniques. CE/FT-IR based on a solvent elimination approach has three major obstacles: (1) electrical contact for normal CE operation, (2) buffer interference in IR detection,  (3) small sample deposition size for increased IR sensitivity.

   We have designed metal nebulizer CE/FT-IR interface according to the above considerations and successfully collected CE/FT-IR spectra with a volatile ammonium acetate buffer system. The result show CE/FT-IR spectra almost do not need buffer subtraction when an ammonium acetate buffer is used. The sample deposit size from the metal nebulizer is about 200 mm.  The metal nebulizer CE/FT-IR interface is applicable to qualitative and quantitative analysis, CE fraction preparation, and investigation of CE mechanisms and theory.

* Published in Proc. 11th Int. Conf. Fourier Transform Spectrosc.,Am. Inst. Phys. Conf. Proceedings 407, 1997