Electrochromatographic Methods: Capillary Electrochromatograpy
Capilary electrochromatography is a separation technique that brings together advantages of liquid chromatographic selectivity with high efficiency of CE provided by flat flow profile of the electroosmosis. This chapter provides the basic knowledge on gen
- PDF / 2,557,354 Bytes
- 31 Pages / 439.37 x 666.142 pts Page_size
- 14 Downloads / 172 Views
Electrochromatographic Methods: Capillary Electrochromatograpy Michał Szumski
Abstract Capilary electrochromatography is a separation technique that brings together advantages of liquid chromatographic selectivity with high efficiency of CE provided by flat flow profile of the electroosmosis. This chapter provides the basic knowledge on generation of the EOF in capillary electrochromatography and parameters that influence it. Furthermore, attention is paid to the methods used for gradient elution in CEC, which have been one of the problems that restrict the wide use of CEC in chemical laboratories. The chapter also describes the problem of bubble formation in CEC and provides a step-by-step guide of how to perform CEC separation. Moreover, methods of preparation of CEC columns are discussed, including preparation of packed and monolithic silica and polymeric beds. The position of CEC among other contemporary separation methods is also discussed. Capillary electrochromatography (CEC) is a liquid phase separation method using electroosmotic flow to increase separation efficiency in comparison to liquid chromatography. In numerous papers CEC is regarded as a hybrid of capillary electrophoresis and liquid chromatography (HPLC, TLC), which however, is not totally correct. A common characteristic of CE is using one of the electrokinetic phenomena—electroosmosis (EOF)—to move a mobile phase across the stationary phase. It is well known that this phenomenon is not responsible for electrophoretic separation mechanism and it can, but not necessarily, accompany it. A common feature of liquid chromatography is using separation mechanism; however, it has been pointed out in some works that the electric field present during separation may have some influence on the division of the analytes between mobile and stationary phases; hence, the separation mechanisms in CEC and HPLC are not
M. Szumski (&) Faculty of Chemistry, Nicolaus Copernicus University, Torun´, Poland e-mail: [email protected]
B. Buszewski et al. (eds.), Electromigration Techniques, Springer Series in Chemical Physics 105, DOI: 10.1007/978-3-642-35043-6_9, Springer-Verlag Berlin Heidelberg 2013
159
160
M. Szumski
identical. Therefore, electrochromatography can be regarded as an independent separation technique. The first reports on possibilities of using electroosmosis were given by Strain (1939—electrokinetic separation of dyes) [1] and Mould (1952—‘‘electrokinetic filtration’’ of polysaccharides on alumina bed) [2]. The concept of fast liquid chromatography using electroosmosis for ‘‘pumping’’ of eluent through a microcolumn (dc = 1 mm) packed with an adsorbent or along the chromatographic plate (TLC) was proposed by Pretorius [3]. The obtained efficiencies were worse than in LC counterpart, but it was so likely due to poor Joule heat dissipation and problems with construction of the setup. It was in 1981 that Jorgenson and Lukacs first performed CEC separation, using packed 170 lm i.d. capillary, in a manner that is followed till the present times[4].
Data Loading...
