preconcentration based on electrostatic interaction between the analytes and

仪器资料 · 发表于 2018-7-23 15:02:10

preconcentration based on electrostatic interaction between the analytes and capillary inner surface
An online preconcentration method based on electrostatic interaction between the
analytes and inner surface of the capillary column was developed for the determination
of zwitterionic analytes such as amino acids in CE coupled with a DAD. The amino
acids possessed positive charges when they were dissolved in an acidic solvent. When
they were injected into the column, they were attracted by the negatively charged inner
surface of the fused-silica capillary column. An etched column was used to increase
the area of the capillary’s inner surface and, consequently increase the electrostatic
interaction between the amino acids and the inner surface of the capillary column. It
was found that when the sample was injected at 10 psi for 1 min and the pH value of
the sample was 4, the amount of amino acids attracted to the inner surface of the
capillary was maximum. Under these optimized experimental conditions, the detection
sensitivity of CE-DAD was enhanced by 5200, 2800, and 3100 times for asparagine,
tryptophan and phenylalanine, respectively, compared with normal CE separation. The
method provided good reproducibility in terms of both migration time and peak height.
It can be successfully used for the preconcentration zwitterion.

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