Introduction to Capillary Electrophoresis

While the term “electrophoresis” was coined in 1909 by Michaelis, 1 it was the pioneering experiments of Tiselius in 19372 that first showed the separation of serum proteins—albumin, and α-, β- , and γ -globulins—by “moving boundary electrophoresis”; this provided the first intimation of the potential use of electrophoretic analysis for biologically active molecules. However, this approach to electrophoresis was limited by the incomplete separation of proteins, the relatively large sample volume needed, and the necessity of relatively low electrical fields due to the convection currents generated by Joule heating, even in the presence of dense sucrose solutions. The historical events that followed in electrophoretic method development were paradigm shifting—for historical detail, the reader is referred to two reviews in the journal Electrophoresis , one by Hjertén 3 in the late 1980s and the other by Rilbe 4 in the mid-1990s. The 1940s saw major efforts directed at improving anticonvective media for zone electrophoresis, while paper electrophoresis was shown to be applicable to the analysis of a wide variety of molecules. 5 , 6 Gels formed from starch 7 and, later, agarose 8 , 9 were developed for the analysis of peptides, proteins, and oligonucleotides. In the 1950s, Kolin 10 attempted isoelectric focusing (IEF), but the absence of “ampholytes” led to short pH gradients that had poor stability over time. It was in this period that the pioneering work of Hjertén 3 laid the groundwork for the capillary electrophoresis (CE)analysis of diverse analytes, ranging from small molecules (inorganic ions, nucleotides) to proteins and viruses. Much of this work was conducted with a functional CE-like instrument, albeit with 3 mm tubes that Hjertén constructed as early as 1959 (see Figure 1.1 ). Figure 1.1 Photograph of the CE system designed by Hjertén. On the left are stacked the high voltage supply and electronic components for the detector, topped off by a strip-chart recorder. In the center is the carriage with the capillary and the electrode vessels above the immersion bath, while the cooling reservoir flanks it on the right. The CE system designed by Hjertén features the high voltage supply and electronic detector components stacked on the left, topped by a strip-chart recorder. At the center is the carriage holding the capillary and electrode vessels, positioned above the immersion bath, while the cooling reservoir is located to the right. https://www.w3.org/1999/xlink" xlink:href=" https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429128370/78feaa72-2f80-42c1-9951-727eeac40591/content/fig1_1.jpg "/>