本研究以紫光/發光二極體(波長410 nm, 2 mW)為螢光激發光源,配合毛細管電泳-線上掃集濃縮技術/誘導螢光偵測法,成功偵測到尿液中微量的多巴胺。這方法是藉由NDA (naphthalene-2,3-dicarboxaldehyde)做為螢光標識試劑,與多巴胺進行衍生反應以後,以螢光偵測的方式進行測量。研究結果發現,以SDS(十二烷基磺酸鈉)為界面活性劑的毛細管微胞電動層析(MEKC)與掃集-毛細管電泳法(sweeping-MEKC)進行分離時,電泳結果所得到的譜峰其理論板數分別為1 × 105、2 × 105;偵測極限為9.1 × 10-7 M與1.2 × 10-8 M。若以sweeping-MEKC的分離模式,且在樣品基質(sample matrix)與背景緩衝溶液(background electrolyte)之間,添加一截甲醇區段,不僅可以延長樣品進樣的體積,使偵測極限到達4.7 × 10-9 M,SDS微胞被甲醇層先破壞後重組的過程之後,理論板數甚至能增加到 1 × 106。
Uses and limitations of a methanol plug assisted sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method are described. Dopamine labeled-NDA (naphthalene-2,3-dicarboxaldehyde) was selected as the model compound; this new method is also applied to the determination of dopamine in actual urine samples. An inexpensive violet light-emitting-diode (LED) was used for the light source because this is suit for fluorescence excitation. The number of theoretical plates of the analyte was determined to be ~ 1 × 105 and ~ 2 × 105 by means of a MEKC and sweeping-MEKC and this was improved to ~ 1 × 106 when the methanol plug assisted mode was applied. In addition, the detection limit of NDA-labeled dopamine was determined to be 9.1 × 10-7 M and 1.2 × 10-8 M by means of MEKC and sweeping-MEKC and this was improved to 4.7 × 10-9 M when the methanol plug assisted sweeping-MEKC mode was applied.