On-line wall-free cell for laser-induced fluorescence detection in capillary electrophoresis |
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Authors: | Chang-Zhu Yu You-Zhao He Hai-Yang Xie Yong Gao Wu-Er Gan Jun Li |
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Affiliation: | 1. Department of Chemistry, University of Science and Technology of China, Jinzhai Road 96, Hefei, Anhui 230026, China;2. School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, China |
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Abstract: | A wall-free detection method based on liquid junction in a capillary gap was proposed for laser-induced fluorescence (LIF) of capillary electrophoresis (CE). The capillary gap of the wall-free cell was fabricated by etching a 10-mm × 50-μm I.D. fused-silica capillary to obtain a polyimide coating sleeve, decoating about 6 mm at one end of both 50 μm I.D. separation and liquid junction capillary, inserting the treated capillary ends into the coating sleeve oppositely, fixing the capillaries with a gap distance of 140 μm by epoxy glue and removing the coating sleeve by burning. The theoretical model, experimental results and wall-free cell images indicated that the gap distance and applied voltage were main influence factors on the wall-free detection. Since the wall-free cell increased the absorption light path and avoided the stray light from the capillary wall, it improved the ratio of signal to noise and limit of detection (LOD) of CE-LIF. Three flavin compounds of riboflavin (RF), flavin mononucleotide sodium (FMN) and flavin adenine dinucleotide disodium (FAD) were used to evaluate the wall-free detection method. Compared with on-column cell, the LODs of the wall-free cell were improved 15-, 6- and 9-fold for RF, FMN and FAD, respectively. The linear calibration concentrations of the flavins ranged from 0.005 to 5.0 μmol/L. The column efficiency was in the range from 1.0 × 105 to 2.5 × 105 plates. The wall-free detection of CE-LIF was applied to the analysis of the flavins in spinach and lettuce leaves. |
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Keywords: | Capillary electrophoresis Wall-free detection Laser-induced fluorescence Flavin Vegetable |
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