Study On Capillary Electrophoresis With Dialysis Sampling Function

Macromolecules and particles are troublesome when small molecules in real samples such as biological samples and environmental samples are analyzed by capillary electrophoresis (CE), so it is really desirable to couple sample clean-up technologies with CE. Off-line coupled sample preparation, which is the most commonly used mode, may cause great sample loss and contamination; also it is tedious and time consuming. So on-line or in-line sample clean-up technologies are badly needed to further the application of CE in complex matrixes analysis. In this paper, a novel method, which is very simple, of in-line dialysis capillary electrophoresis was established. A polysulfone membrane was prepared in the inlet end of the separation capillary by phase-inversion process, which endued the capillary with an additional function of clean-up sampling. The capillary can be directly used for clean-up sampling and in-line electrophoresis separation of small molecules in complex sample. The preparation process and performance of the system was studied in detail and several applications with satisfactory results were performed. The main research and results are as below: 1. A novel CE method with dialysis sampling function was established and its performance was studied. A polysulfone membrane was prepared in the inlet end of the separation capillary by phase-inversion process, which endued the capillary with an additional function of clean-up sampling. The membrane cut off macromolecules and particles efficiently and persistently. As the membrane was formed in situ, there is almost no dead volume. Using this capillary in electrophoresis, column efficiency with little reduction was achieved and the RSDs of migration times and peak areas of chlorpheniramine were 0.8% and 4.6%, respectively. During continuous use of this capillary for 12 hours, the performance of the membrane changed little. Both electrokinetical injection and equilibrium dialysis injection was available. 2. The molecule weight cutoff of the membrane (sample cleanup ability) could be controlled by the control of the formula of the casting solution, which enhanced the flexibility of the method. In order to improve the detection sensibility, electrochemical detection method was developed, which extended the application field of this method. 3. This technology has been applied in the analysis of free caffeine in Coffee Milk Drink. Without any sample preparation, Coffee Milk was injected and analyzed. Little interference was observed, and the concentration was determined to be 0.68 mmol·L-1. 4. By applied this method into the evaluation of the molecule interaction, the binding constant of promethazine hydrochloride with BSA was obtained, that is 1.47×104 L·mol-1. In this method, the interfere of macromolecules which exist in common capillary electrophoresis interaction methods was eliminated, so the method is promising in the interaction analysis between macromolecules and small molecules. 5. This method was also applied into the determination of glucose in human blood. Electrochemical detection with copper microelectrode as working electrode was adopted. Whole blood was diluted and injected directly. The concentration of blood sugar was 5.53 mmol·L-1,and the limit of detection was 0.1 mmol·L-1. The technology may be further used to monitor the endogenous or exogenous small molecules and their metabolites, which may contribute to studies in life science and pharmaceutics. Furthermore, as the capillary could be inserted into the animal's vein and equilibrium dialysis injection was available, this method may be used for in vivo analysis.