| As the quest for modernization of traditional Chinese medicineprogresses, the demand for more powerful analytical tools becomes muchurgent. This phenomenon has brought great challenge to the diversity andadvancement of analytical and detection methods. One kind of traditionalChinese medicine may be a system of more than one hundredcomponents. New chemical constitutes also could be discovered asscience advances. Moreover, in the process of preparation of the herbalmedicine compounds, more ingredients may be produced. So it is nodoubt that the quality control of traditional Chinese medicine presents acomprehensive challenge. Evaporative scattering light detector could beused to detect any samples that have a lower volatility than the mobilephase. As an universal detector, it poses advantage of wide gradientcompatibility and no limitation on choice of solvents, especially when itis used for herbal medicine quality and food safety control. Nowadays,herbal medicines, or more widely natural products, is developing rapidlyworldwide. It is an integrated part of the rapidly expanding global“eco-fashion”. Ginkgo biloba is an ideal representative that falls into thecategory of modern herbal medicine. As ultraviolet-visible (UV/Vis)detection is popular and could provide good sensitivity. A part of thisstudy has been focused on the combination of UV with ELSD in series,and investigation on the analysis of Ginkgo biloba extract. The maintherapeutic components, terpene lactones were also determined. Single detector (UV/Vis) fingerprints method was further integrated with asecond detector (ELSD), establishing an improved binary detectorfingerprint analysis method. On the other hand, apparatus minimization isone of the main branches in analytical instrument development, widelyapplicable in biomedical and high-throughput drug screening areas. Inthis study, we also investigated the optimization of the spray methods inminiaturized ELSD (μELSD). The μELSD was coupled to capillaryseparation systems, resulting in separation of several samples: thecomplex traditional Chinese medicine sample Ginkgo biloba extract, itsdisperse tablet sample, the flavonoids and terpene lactones. All thesestudies expanded the application range of capillary liquidchromatography (cLC) and pressurized capillary electrochromatography(pCEC). This presents a powerful tool in complex sample analysis.There are five chapters in this dissertation, in which the maincontents are as following:The first chapter described the basic background on the mechanismand detection procedure of ELSD. Then introduced the outlook of Ginkgobiloba extract and its quality control. Moreover, conventional detectorsthat could couple to capillary separation system were summarized.Meanwhile, the development of light scattering detectors that could becoupled to capillary separation system were illustrated in detail.In chapter two, high-performance liquid chromatography (HPLC)with UV/Vis detection, followed by ELSD platform (HPLC-UV-ELSD)was established. Ginkgo Biloba extract was successfully separated withfour main terpene lactones (Ginkgolide A, B, C and bilobalide)determined. Better result was obtained in70/30(v/v) methanol/watersystem and ultrasound for60min. Solvent A (0.05%aqueous TFA) andSolvent B (isopropanol) were used for gradient elution with the followingprogram:5-20%B within50min, then kept constant until80min.An approach of binary fingerprint analysis method was developed inthe third chapter, which could provide more comprehensive informationon Ginkgo Biloba extract system. Fingerprints for ten batches of Ginkgobiloba extract, from various origins of manufacturers in China (Shanxi,Beijing, Shandong, Zhejiang, Guangdong, Jiangsu, Tianjin, Hunan) were firstly obtained. Similarity Evaluation System for ChromatographicFingerprint of traditional Chinese medicine was utilized, for thegeneration of UV and ELSD reference fingerprints and fingerprintsimilarities. SPSS were conducted to obtain main component analysis andhierarchical cluster analysis. The differentiation was shown in3D Plot.Finally, the single detector fingerprints were further combined to get anintegrated method for fingerprint analysis. The result of the combinedanalysis method indicates a promising method for providingcomprehensive information, which suggests potential applicability inherbal medicine quality control.Chapter four investigated the oprimization of the spray methods ofminiaturized evaporative light scattering detector: electrospray and gasspray. An off-line electrospray platform was established and tested. Thespray distance was explored according to different spray pipelinematerials,10electrospray capillary locations,6diameters and5electrodemodes were tried out. This lays a foundation for the future study ofelectrospray in ELSD miniaturization. In addition, the nebulizationsystem was further investigated by reducing the inter-space between theinner diameter of the stainless steel nozzle and the outer diameter of thecapillary spray needle from40μm to25μm, the nebulization gasflowrate was effectively decreased below1L/min. The drift tubetemperature, nebulization gas flow and organic phase proportion ofmobile phase on quereetin response were also optimized. It proved thatincreasing evaporization temperature of drift tube, nebulization gas flowand organic phase proportion could lead to a higher signal to noise ratio.In chapter five, we moved on to the coupling of μELSD with thecapillary separation system. Application were carried out on the analysisof Ginkgo biloba extract, its disperse tablet formulation, and terpenelactones with pretty weak absorption in the UV detection. Based on thehighly effective advantage of pCEC, the pCEC-μELSD separation anddetection system was established. The separation efficiency of terpenelactones and flavonoids was improved when using this platform. Thislays a solid foundation for μELSD advancement in traditional Chinesemedicine analysis. |
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