Studies On Microchip Capillary Electrophoresis System With Solid-phase Extraction

Using riboflavin and flavin mononucleotide as model analytes, the present work studies online combination of solid-phase extraction (SPE) with microchip capillary electrophoresis (CE).In the first chapter, the recent development of the solid-phase extraction coupled to microchip was reviewed. Diversity combination technique was introduced. Their advantages and disadvantages were discussed.In the second chapter, a microchip capillary electrophoresis with laser-induced fluorescence detector (CE-LIF) was constructed for separation and detection of riboflavin and flavin mononucleotide. The chemical and biochemical properties of riboflavin and flavin mononucleotide and their function in organism were presented first. Then, experiment parameters were studied. Under optimized conditions (5.0 mmol/L phosphate buffer at pH 7.00, 2500V separation voltage), baseline separation of riboflavin and flavin mononucleotide was achieved in about 1 min. Riboflavin impurity in synthetic flavin mononucleotide (sodium salt) was detected by the proposed method. Riboflavin impurity's content was about 3 percentage which was in agreement with manufacturer's specification.The third chapter was about online coupling of sequence injection solid-phase extraction preconcentration to microchip capillary electrophoresis (SI-SPE-CZE). An interface was designed to couple three systems. Under optimized conditions (a solution containing 80% methanol and 20% 5.0 mmol/L phosphate buffer at pH 7.00 as eluent; 5.0 mmol/L phosphate buffer at pH 8.00 as electrophoresis running buffer; 13.3 μL/s for sample flow rate and 20 μL/s for elution flow rate; -1000V sampling voltage), the coupled system worked steadily. Using riboflavin as model analyte, a concentration enhancement factor 12.6 and a concentration limit of detection of 0.1 μmol/L were achieved. Finally, the difficulties and limitation of the coupled SI-SPE-CE system was discussed.