In CE analysis, the selectivity was adjusted by changing the pH
and BGS concentration. Therefore, in our studies, the effect of Tris
concentration was observed in a range from 5 to 60 mM. Fig. 3A
showed that the peak heights of the two analytes, as well as the
resolution between them, reached the largest values with a concentration
of 20 mM. This could be explained by the fact that the
increase in Tris concentration could reduce the absorption of the
analytes to the capillary wall, which slowed down the EOF. A slow
EOF was helpful to the sweeping process. At the same time, the
ionic strength of the BGS increased, which resulted in an enhancement
in the conductance of the BGS. If the specific conductance of
the BGS was too high, the Joule heat production would increase,
and high system temperatures led to extra peak broadening and
a decrease in resolution (Beckers & Bocˇek, 2003). Therefore, in
consideration of the resolution, peak shapes, and peak heights of
the analytes, the optimal concentration of Tris was chosen as
20 mM