title: Etched bare fused-silica capillaries for online preconcentration of amino acids in CE.
abstract: 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.
authors.affiliation: Jiangsu Key Laboratory of Environmental Materials and Environmental Engineering, College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, P. R. China. quqishu@gmail.com
authors.forename: Qishu
authors.initials: Q
authors.lastname: Qu
authors.forename: Yin
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Tang
authors.forename: Chengyin
authors.initials: C
authors.lastname: Wang
authors.forename: Gongjun
authors.initials: G
authors.lastname: Yang
authors.forename: Xiaoya
authors.initials: X
authors.lastname: Hu
authors.forename: Chao
authors.initials: C
authors.lastname: Yan
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000302:isolation & purification*; D001216:Asparagine / Q000737:chemistry / Q000302:isolation & purification; D019075:Electrophoresis, Capillary / Q000379:methods*; D017022:Flow Injection Analysis; D006863:Hydrogen-Ion Concentration; D010649:Phenylalanine / Q000737:chemistry / Q000302:isolation & purification; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000737:chemistry*; D055672:Static Electricity; D014364:Tryptophan / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D010649:Phenylalanine; D001216:Asparagine; D012822:Silicon Dioxide; D014364:Tryptophan