The Analysis Of Several TCMs By MEEKC Based On Ionic Liquids

The determination of active compounds in Traditional Chinese Medicines (TCMs)have been a hot topic in the Analytical Chemistry field for many years. There arevarious kinds of compounds in the TCMs and some of them may vary with differentcollecting districts and seasons, which makes it more difficult to analyze them. Thereare mainly four challenges for TCMs analysis.1) Complex constituents in TCMs.2)Various isomers in TCMs.3) Strong polarity components such as proteins andnucleosides.4) Unstable ingredients in TCMS. Microemulsion ElectrokineticChromatography (MEEKC) was established in1990s based on Micellar ElectrokineticChromatography (MEKC). MEEKC can separate acidic, basic and neutral compoundssimultaneously with good resolution, which makes MEEKC suitable for separatingsome multi-compounds in complex samples, so MEEKC has also found increasing usein natural products analysis. Actually, ionic liquids are moltens alts and have beentestified that they are more environmentally attractive than organic solvents, They arereceiving more and more attentions because of their special physical and chemicalproperties. The prevalent use of ionic liquids has been hindered by the low solubility ofsome substances in ionic liquids. For the sake of tackling the problem above, combiningmicroemulsion with ionic liquids is an ideal way. The microemulsion based on ionicliquids can find widespred use because it owns characters of both microemulsion andionic liquids, actually it has been applied in many fields currently. The purpose of thisthesis is to develop a new kind of MEEKC with hydrophobic ionic liquids [BMIM]PF6as oil phase, and then find its application in separation and determination of some activecompounds in several TCMs. The thesis mainly consists of five parts just as follows:The first part of this thesis is a reviw about the application of normal MEEKC andMEEKC based on ionic liquids.In the second part, a rapid and repeatable microemulsion electrokineticchromatography (MEEKC) method was developed for the simultaneous determinationof three isomers (α-, β-and γ-asarone) in Acorus tatarinowii by using ionic liquid1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) as oil phase. Finally,the main compounds in the methanol extract of Acorus tatarinowii were well separatedwithin11min.The developed method was applied to determine the contents of α-, β-and γ-asarone in Acorus tatarinowii from five different producing areas in China (Anhui, Hebei, Sichuan, Zhejiang and Chongqing). On the other hand, the microemulsionelectrokinetic chromatography with ionic liquid as oil phase should be a promisingmethod for the analysis of volatile components in medicinal herbs.In the third chapter, four nucleobases, four nucleosides, and two nucleotides weresimultaneously determined by MEEKC with ionic liquid1-butyl-3-methylimidazoliumhexafluorophosphate ([BMIM]PF6) as oil phase. Finally, the ten compounds were wellseparated within11min. The developed method was successfully applied to determinethe contents of investigated compounds in three different widely used traditionalChinese medicines (cultured Cordyceps sinensis, Radix Astragali, and Radix Isatidis).The results indicated that the developed MEEKC method could be used for the rapiddetermination of nucleobases, nucleosides, and nucleotides in herbal medicines or othercomplex matrices.Curcuminoids have been proved to degradate easily under alkaline conditions,while most analysises of curcuminoids were carried out under alkaline conditions (dueto the strong solubility), in the fourth chapter, the stability of curcuminoids (curcumin,demethoxycurcumin, bis-demethoxycurcumin) in different solutions (boric acid buffer,microemulsion with n-octane as oil phase+boric acid buffer, microemulsion with ionicliquid ([BMIM]PF6) as oil phase+boric acid buffer) were investigated. The resultsindicated that microemulsion systems have significant protective effect on the analyteseven under alkaline conditions as compared to boric acid buffer only, whilemicroemulsion with ionic liquid showed the best protecting effect. Therefore, a stableand rapid microemulsion electrokinetic chromatography (MEEKC) method with ionicliquid as oil phase was developed for simultaneous determination of the threecurcuminoids in rhizome (Jianghuang) and tuberous root (Yujin) of Curcuma longa.Finally, the investigated curcuminoids were well separated within9min. The developedmethod was successfully applied to determine the contents of investigated curcuminoidsin four real samples (Yujin from Chengdu and Leshan, Jianghuang from Chengdu andLeshan). All of the results showed that the MEEKC with ionic liquid as oil phase shouldbe an ideal choice for the analysis of curcuminoids by CE.The fifth part summarized the experimental sections and some improvement weshould be done in the future work.