In the present paper, a laboratory-made high-performanceelectrophoresis microcolumn unit was prepared for UV-Vis spectrophotometer. X-raydiffraction was used in the preparation of electrophoretic microcolumns. And ananalytical technique of microcolumn electrophoresis coupled with UV-Visspectrophotometry was introduced. Uniform quartz microncrystals were prepared byhydrothermal synthesis. Their crystalline phase and morphology were identified byX-ray diffraction and scanning electron microscope, respectively. The quartzmicroncrystals were packed into a 2-mm i.d. fused-silica tube to prepare theelectrophoretic microcolumn. With 1.5 mmol?L-1 disodium phosphate buffersolution (pH 11.5) containing 25% (φ) methanol and 10% (φ) acetonitrile,tryptophan, phenylalanine and tyrosine were on-line separated on line anddetected by microcolumn electrophoresis coupled with UV-Vis spectrophotometrywithout derivatization. The limits of detection were 0.037, 0.20 and 0.20 μmol?L-1, respectively. The separation efficiency of tryptophan was 4.5×104 plates/m.The sample capacity of the electrophoretic microcolumn achieved 35 μL. It wasfound that the electrophoretic microcolumn packed with quartz microncrystals wasable to limit Joule heat, increase sample capacity and enhance detectionsensitivity. The laboratory-made electrophoretic microcolumn could be a high-performance separation unit for conventional UV-Vis spectrophotometer. The on-line coupling of microcolumn electrophoresis and UV-Vis spectrophotometry couldseparate and determine samples with complicated matrices, reduce zone broadeningand enhance separation efficiency, so expand the analytical function ofspectrophotometer in the trace analysis of mixed components with overlappedspectra.spectrophotometer; Hydrothermal synthesis; Quartz microncrystals; X-raydiffraction; Amino acids