| A capillary electrophoresis/light emitting diode（LED） induced fluorescence detector system was designed and constructed especially for the determination of ephedrine and pseudoephedrine in ephedra herb.According to the spectral and chemical characteristics of ephedrine and pseudoephedrine,the main parts of apparatus were chosen as follows:a blue LED was used as the light source;two band pass filters including BP 470 filter and BP 530 filter were used for the emission light and the fluorescence,respectively,and photomultiplier tube（PMT） was used as the detection element.The buffer concentration and the separation voltage were optimized.Fluorescein isothiocyanate（FITC） was chosen as the label probe,and 10 mmol/L Na2B4O7（pH 9.3）+16 mmol/L SDS was used as running buffer.Under the optimal conditions,a baseline separation of two compouds in ephedra herb was achieved under the separation voltage of 12 kV.The method showed good linearity over the concentration range of 0.25-10 mg/L for the two compounds with correlation coefficient more than 0.99.The limits of detection（S/N=3） for ephedrine and pseudoephedrine were 0.38 μg/L and 0.29 μg/L,respectively.The intra day RSDs for ephedrine and pseudoephedrine were 2.0% and 2.2%,and the inter-day RSD were 5.4% and 5.1%,respectively.The method was successfully used in the analysis of ephedra herb with recoveries of 94% for ephedrine and 107% for pseudoephedrine. |