Multi‐wavelength light emitting diode array as an excitation source for light emitting diode‐induced fluorescence detection in capillary electrophoresis

Abstract

A multi-wavelength LED array was used as an excitation source for in-column fiber-optic LED-induced fluorescence for CE. The light source consisted of a multi-wavelength LED array consisting of three different LEDs (430, 450 and 480 nm), a focusing lens and a gradient index lens group. The LED beam was collimated and reshaped with the gradient index lens group for coupling the LED light source into a single-mode optical fiber. In addition, the luminance and stability of the LED light source was improved by powering the LED under constant current at enhanced voltages. The benefits of this system were demonstrated by the simultaneous determination of FITC-labeled L-asparagine (Ex/Em 488/520 nm), 4-fluoro-7-nitro-2,1,3-benzoxadiazole-labeled epinephrine (Ex/Em 468/530 nm) and 3-(4-carboxybenzoyl)-quinoline-2-carboxaldehyde-labeled L-leucine (Ex/Em 440/530 nm). Detection limits of L-asparagine, epinephrine and L-leucine were estimated to be 0.8 x 10(-9), 12.0 x 10(-8) and 4.0 x 10(-8) M (S/N=3), respectively. The RSDs (n=6) for migration time and peak area were better than 0.71 and 0.92%, respectively. The performance of the developed multi-wavelength LED excitation source was compared to the use of a single-wavelength LED and found to provide superior sensitivity for the three fluorophores used in this study.

Signal-to-noise ratio enhancement of the compact light-emitting diode-induced fluorescence detector

“…capillary. To our knowledge, except in this work, LODs of most LED-FDs reported so far were at the nano molar level [11][12][13]. The value next to the lowest was 0.29 nM which was reported by Dan Xiao's group [10].…”

“…The LOD was evaluated by FIA with a capillary flow cell of 250 mm i.d. The LOD value of 0.75 nM was already among the lowest in literature [11][12][13].…”

A compact and highly sensitive light-emitting diode-induced fluorescence detector for capillary flow systems

“…Because there had never been a standard evaluation conditions for LED-FD, the sensitivity was roughly estimated by us. For CE methods, because of the zone concentration effect, the SNR was generally enhanced by several times when the sample was prepared in a buffer much diluter than the running buffer [13,14]. For FIA methods, there is no such concentration effect, but there is a dilution effect instead [11].…”

“…Therefore, the light intensity at the detection cell was partly impaired. Recently, LED-FDs that were constructed by using optical lens system and excitation fiber together reached the sensitivity of 10 −10 M [13,14].…”

HPLC with In-Capillary Optical Fiber Laser-Induced Fluorescence Detection of Picomolar Amounts of Amino Acids by Precolumn Fluorescence Derivatization with Fluorescein Isothiocyanate

“…Recently, our research group has successfully developed in-column optical fiber induced-fluorescence detection system for capillary electrophoresis (CE) [16][17][18][19][20][21][22][23][24][25]. For the in-column optical fiber induced-fluorescence detection system, our previous work demonstrated that an excitation light beam waveguided by an optical fiber to the detection point of the capillary shows relatively lower background light than that obtained from an excitation light beam impinged orthogonally on the capillary exterior wall.…”