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

Figure 17
Influence of buffer concentration on
BSA tryptic digest separations
Conditions: Phosphate buffer pH 7, V = 25kV,
i = 9, 36, and 71 mA, respectively,
l = 50 cm, L = 58.5 cm, id = 50 mm,
od = 375 mm, BSA concentration
= 2 mg/ml, injection = 100 mbar s
mAU
10 mM
Principles
50 mM
100 mM
Elution order
Whale skeletal myoglobin
Horse heart myoglobin
Carbonic anhydrase B
Carbonic anhydrase A
β-lactoglobulin B
β-lactoglobulin A
6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00
Time [min]
to 10), both the wall and the sample will be deprotonated
and negatively charged, and solute-wall interactions will be
limited by charge repulsion (figure 18).
4.0 6.0 8.0
Time [min]
Figure 18
CZE of proteins using buffer pH above
solute pI 7
Conditions: 20 mM borate pH 8.25, V = 30 kV,
l =55 cm, L = 101 cm, id = 52 mm
Coating the capillary wall is a useful method for decreasing
solute adsorption by decreasing the free energy of interaction.
Coatings can take various forms, including simple
addition of dynamic deactivation with buffer additives (that
is, hydrophilic polymers or detergents) or covalent modification
of the wall. Both can be used to eliminate or reverse
the charge on the wall, alter hydrophobicity and limit nonspecific
adsorption. More information regarding coatings
and protein separations can be found in section 3.1.2.
39