Study On The Surfactant Compatible With Micellar Electrokinetic Chromatography-mass Spectrometry

Micellar electrokinetic chromatography-mass spectrometry (MEKC-MS) seems extremely attractive and advantageous, as it would combine a highly versatile separation technique of MEKC with mass-selective and structure-elucidative detection. MEKC is suitable for the analysis of neutral and charged analytes, while CZE is only used for the charged ones. MEKC-MS is a good solution to the efficient separation performance and the qualitative analysis with retention time alone may have the problem of poor reliability of the results when analysis the compositions of the complex sample. However, non-volatile surfactants and buffer systems used frequently in MEKC would reduce the efficiency of atmospheric pressure electric spray ionization (ESI) source and pollute ion source, which may cause the limitation of MEKC-MS. In this thesis, a series of surfactants with different groups and different carbon chains were synthesised based on lauric acid surfactant which was applicable in MEKC-MS. The structures of these surfactants were characterized and the MEKC-MS compatibilities of these surfactants were tested. Finally, a novel micellar electrokinetic capillary chromatography-electrospray ionization mass spectrometry method for the determination of4effective components in Qingwei Huanglian Pills was established using lauroyl malate as the surfactant.This thesis reviewed the development and advantages of micellar electrokinetic chromatography-mass spectrometry technology, and the synthesis and characterization of surfactants, the following aspects were mainly investigated:1. Fifteen surfactants were synthesized, including one Gemini surfactant: di-lauroyl tartaric acid ester; five anionic surfactants:lauroyl citric acid ester, lauroyl ascorbic acid ester, lauroyl malic acid ester, lauroyl mandelic acid ester, lauroyl sulfosalicylic acid ester; six amphoteric surfactants:lauroyl glutamic acid, lauroyl glycine, lauroyl valine, lauroyl phenylalanine, lauroyl cysteine, lauroyl methionine; and three nonionic surfactants:lauroyl maltose ester, lauroyl glucose ester, lauroyl fructose ester. These fifteen surfactants were characterized by means of high performance liquid chromatography, mass spectrometry and infrared spectroscopy.2. Critical Micelle Concentration (CMC) and MEKC-MS compatibility of different synthesized surfactants were tested. The influence to the compatibility of those surfactants on MEKC-MS was investigated. It was found that the lauroyl malic acid ester was the best of them.3. Six fatty acyl malic acid ester surfactants with different carbon chains were synthesized and characterized, and then the MEKC-MS compatibility was tested. The influence of carbon chain length of fatty acyl malic acid ester surfactant to MEKC-MS compatibility was investigated. It was found that the lauroyl malic acid ester was most compatible with MEKC-MS.4. A method of Micellar Electrokinetic Chromatography-Electrospray Ionization-Mass Spectrometry (MEKC-ESI-MS) was established for simultaneous determination of coptisine, palmatine, paeoniflorin and forsythin in Qingwei Huanglian Pills using lauroyl malic acid ester as surfactant. In uncoated fused silica capillary column (84cm×50μm),20mmol·L-1lauroyl malic acid ester and100mmol·L-1ammonia solution (containing20%acetonitrile, pH8.5) was selected for the buffer solution, separation voltage was25.0kV, injection time was4s,60%isopropanol-water mixture (containing3mmol·L-1acetic acid) was selected for sheath liquid of the electrospray ionization mass spectrometry. The four components were completely separated within15min. Therefore, lauroyl malic acid ester could be a new surfactant instead of lauric alternate.