High performance capillary electrophoresis - T.E.A.M.

Principles
2.1 Historical
background and
development
25-75 cm
25-75 µm
300-400 µm
5-25 cm
Electrophoresis has been defined as the differential movement
of charged species (ions) by attraction or repulsion in
an electric field. Electrophoresis as a separation technique
was introduced by Tiselius in 1937. Placing protein mixtures
between buffer solutions in a tube and applying an electric
field, he found that sample components migrated in a
direction and at a rate determined by their charge and
mobility. For his work in separation science Tiselius was
awarded a Nobel Prize.
Separation efficiency in free solution, as performed by
Tiselius, was limited by thermal diffusion and convection.
For this reason, electrophoresis traditionally has been
performed in anti-convective media, such as polyacrylamide
or agarose gels. Gels in the slab or tube format have been
used primarily for the size-dependent separation of biological
macromolecules, such as nucleic acids and proteins.
Although it is one of the most widely used separation
techniques, slab gel electrophoresis generally suffers from
long analysis times, low efficiencies, and difficulties in
detection and automation.
An alternative to the slab-format is to perform the electrophoretic
separation in narrow-bore tubes or capillaries
(figure 2). Since narrow capillaries are themselves anticonvective,
gel media are not essential to perform that
function. This allows the performance of free-solution (or
open tube) electrophoresis, as well as the use of traditional
gel media in the capillary.
5-25 cm
1-2 cm
Figure 2
Comparison of gel used for slab
electrophoresis and capillary for HPCE
Initial work in open tube electrophoresis was described by
Hjérten in 1967. At that time, since only millimeter-bore
capillaries were available, Hjérten rotated them along their
longitudinal axis to minimize the effects of convection. Later
Virtanen and then Mikkers performed electrophoresis in
approximately 200-µm internal diameter (id) capillaries
made from glass and Teflon, respectively. In the early 1980s
Jorgenson and Lukacs advanced the technique by using
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