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
(*已发表在光谱学与光谱分析，18，73，1998)
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GC、HPLC 和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-IR和SFC/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 是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.