title: UV light-emitting diode-induced fluorescence detection combined with online sample concentration techniques for capillary electrophoresis.
abstract: The application of an ultraviolet (UV) light-emitting diode (LED) to on-line sample concentration/fluorescence detection in capillary electrophoresis (CE) is described. The utility of a UV-LED (peak emission wavelength at 380 nm, approximately 2 mW) for fluorescence detection was demonstrated by examining both a naturally fluorescent (riboflavin) compound and a nonfluorescent compound (tryptophan), respectively. The detection limit for riboflavin was determined to be 0.2 ppm by the normal MEKC mode, which was improved to 3-7 ppb when dynamic pH-junction technique was applied. On the other hand, the detection limit of the tryptophan derivative was determined to be 1.5 ppm using the MEKC mode, which was improved to 3 ppb when the sweeping-MEKC mode was applied. In an analysis of an actual sample, the concentrations of riboflavin in beer, and tryptophan in urine and milk samples were determined, respectively.
authors.affiliation: Department of Chemistry, National Taiwan Normal University, 88 Sec. 4, Tingchow Road, Taipei, Taiwan.
authors.forename: Yen-Sheng
authors.initials: YS
authors.lastname: Chang
authors.forename: Chun-Min
authors.initials: CM
authors.lastname: Shih
authors.forename: Cheng-Huang
authors.initials: CH
authors.lastname: Lin