Research: Science & Education edited by
Topics in Chemical Instrumentation
Howard A. Strobel Duke University Durham, NC 27708-0354
Capillary Electrophoresis Part I. Theoretical and Experimental Background Christine L. Copper Chemistry Department, United States Naval Academy, Annapolis, MD 21402
Separation is the cornerstone of many areas of chemistry. Quite often, the goal of a chemical experiment is to isolate and analyze a particular compound. The different types of chromatography are unquestionably the most widely used methods of separation in analytical chemistry. However, a somewhat related technique, capillary electrophoresis (CE), also referred to as capillary zone electrophoresis (CZE) and as high-performance capillary electrophoresis (HPCE), is also emerging as a powerful separation tool. Separation in CE is based on differences in solute mobilities when a strong electric field is applied across a separation buffer solution (also known as a running buffer). Compared to conventional liquid chromatographic (LC) techniques (such as high-performance liquid chromatography, HPLC), CE offers advantages of high efficiency, short analysis time, simple apparatus, small sample and separation buffer volumes, and ease in changing the separation buffer (1). Additionally, selectivity in CE separations can be easily altered through the use of different buffer additives. Background Capillary electrophoresis has evolved from what now seem to be rudimentary column electrophoresis techniques that were introduced three decades ago. Early reports, many of which were by Hjerten and Catsimpoolas, employed columns having inner diameters (i.d.’s) on the millimeter scale (2, 3). However, advantages of smaller-diameter columns were soon discovered by Virtanen (4) and by Mikkers, Everaerts, and Verheggen (5). Virtanen used Pyrex tubing with i.d.’s ranging from 200 to 500 µm to quantitatively analyze Li+, Na+, and K+ cations using potentiometric detection. His report is noteworthy for its recognition of the important influence of electroosmotic flow on a solute’s behavior. Mikkers et al. separated a number of inorganic and organic anions using 200 mm i.d. Teflon tubing and UV and conductometric detection schemes. In 1981, Jorgenson and Lukacs performed the first electrophoretic separations in narrow glass capillaries (
