Ch. 30
Capillary Electrophoresis, Capillary Electrochromatography and Field - Flow Fractionation
Electrophoresis = ?
Capillary Electrophoresis = ?

電 泳
: a separation method based on the differential rate of migration of charged species in a buffer solution across which has been applied a dc electric field .
Q / d : charge-to-size ratio
Swedish chemist
1948 Nobel Prize
Serum proteins

Slab electrophoresis
平板
Bio macromolecules:
Proteins (enzyme, hormones, antibodies)
Nucleic acids (DNA, RNA)
L. Stryer, Biochemistry , 4 th ed.,
W. H. Freeman, 1999, p. 47.

F. Rouessac and A. Rouessac, Chemical
Analysis , Wiley, 2000, p.112

Human Genome: sequence for human DNA

Systematic apparatus for capillary electrophoresis
25 ~ 75 μ m i.d.
~ 50 cm long vs. slab eletrophoresis: no joul heating effect
15 ~ 30 kV
G. D. Christian, Analytical Chemistry ,
6th ed., John Wiley, 2004, p. 632

FIGURE 30-1 Schematic of a capillary electrophoresis system.

D. C. Harris, Quantitative Chemical
Analysis , 6 th ed., 2003, p. 655.

buffer solution e.g. Na
+
Ac
-
電 滲 流
Acts as a pump
帶動整體溶液
Microfluid
微流體 electrical double layer
OH pH > 3 O
-
Si Si
FIGURE 30-2 Charge distribution at a silica-capillary interface and resulting electroosmotic flow .

+ =
-
+ >
-
D. C. Harris, Quantitative Chemical
Analysis , 6 th ed., 2003, p. 658.

+
電滲流
電泳
+
charge / size
In general,
ν eo
>
ν e
Separation is based on differences in electrophoretic mobility.
migration velocity
淨移動速率
FIGURE 30-4 Velocities in the presence of electroosmotic flow. The length of the arrow next to an ion indicates the magnitude of its velocity; the direction of the arrow indicates the direction of motion. The negative electrode is to the right and the positive electrode to the left of this section of solution.

flat parabolic electroosmotic hydrodynamic
+ pump
FIGURE 30-3 Flow profiles for liquids under (a) electroosmotic flow and (b) pressure-induced flow.

pump
D. C. Harris, Quantitative Chemical
Analysis , 6 th ed., 2003, p. 658.

ms ms
D. C. Harris, Quantitative Chemical
Analysis , 7 th ed., 2007.

D. C. Harris, Quantitative Chemical
Analysis , 6 th ed., 2003, p. 656.

van Deemter equation:
D. C. Harris, Quantitative Chemical
Analysis , 6 th ed., 2003, p. 656.

• High separation efficiency (N > 10
5
)
• Low reagent consumption
• Low sample consumption (< 10 nL)

1.
Electrokinetic injection
2.
Pressure injection a. pressure b. vacuum c. height difference (gravity)

(UV/Vis)