Anion-selective exhaustive injection-sweeping microemulsion electrokinetic chromatography.
In this study, anion-selective exhaustive injection-sweeping (ASEI-sweeping) technique, which is a selective on-line sample concentration technique, was first proposed in microemulsion electrokinetic chromatography (MEEKC) for analyses of eight acidic phenolic compounds. In contrast to a capillary that is typically filled with nonmicellar background solution in conventional ASEI-sweeping MEKC method, in the proposed ASEI-sweeping MEEKC method, a capillary is filled with a low pH microemulsion solution (pH 2.0), and then with a short acid plug (pH 2.0, 1.9 cm) before field-amplified sample injection. This proposed design has two functions. First, the microemulsion solution that is present at the front of capillary column is able to avoid phase separation of microemulsion solution during MEEKC separation. Second, the presence of the short acid plug would effectively limit the partition behavior of acid analytes with the oil droplets in the microemulsion during field-amplified sample injection; otherwise, the stacking effect of acid analytes would be markedly reduced. This optimal ASEI-sweeping MEEKC method afforded about 96,000-fold to 238,000-fold increases in detection sensitivity in terms of peak areas without any separation efficiency loss when compared to normal MEEKC separation. Furthermore, trace levels (about 3 ng/g) of gallic acid and catechin in foods were also detected successfully by the proposed ASEI-sweeping MEEKC technique.
Huang
Hsi-Ya
HY
Department of Chemistry, Center for Nanotechnology at CYCU, Chung Yuan Christian University, Chung-Li, Taiwan, China. hyhuang@cycu.edu.tw
Lien
Wei-Chih
WC
Huang
I-Yun
IY
D000143:Acids / Q000032:analysis; D000838:Anions / Q000032:analysis; D002392:Catechin / Q000032:analysis; D002853:Chromatography, Liquid / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D004655:Emulsions; D005504:Food Analysis / Q000379:methods*; D005707:Gallic Acid / Q000032:analysis; D009862:Online Systems; D010636:Phenols / Q000032:analysis* / Q000737:chemistry; D012680:Sensitivity and Specificity
D000143:Acids; D000838:Anions; D004655:Emulsions; D010636:Phenols; D005707:Gallic Acid; D002392:Catechin