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Chapter 1 provides a short introduction into the constraints of phytochemical analysis. In order to make them faster, less laborious and greener, there is a clear scope for miniaturized and simplified sample preparation, solvent-free extractions and the use of cleaner solvents in preparative HPLC. Possible modern techniques to achieve this, such as microfluidic chips, ambient mass spectrometry, selective magnetic nanoparticles, and use of less toxic but equally efficient solvents are discussed. Clear aims were formulated and research towards fulfilling these aims in the field of phytochemical analysis is carried out in this thesis.
A first version of a 3-phase liquid-liquid extraction (LLE) chip for the miniaturized sample pretreatment of alkaloids was introduced by our group in 2009. In Chapter 2 more biodegradable and less-toxic solvents for the transport phase and a more suitable pH for the feed phase were evaluated. The extraction efficiency improved. On-line hyphenation of the 3-phase chip to nanoLC-UV/MS was also investigated. This combination saved a lot of time and solvent in comparison with traditional methods for the purification of alkaloids from plant materials.
A novel Induced Phase Separation Extraction (IPSE) chip was introduced in Chapter 3 for efficient sample pretreatment. The acetonitrile – water (1:1) sample solutions were separated in organic and aqueous phases in this IPSE chip based on their affinity for both phases. In turn this could be correlated with the log D values of the analytes. Some optimization regarding design, operation, flows and solvents was carried out. Extraction efficiencies of several model compounds were determined. A real sample application with a plant used in Traditional Chinese Medicines (TCMs) was carried out to show the usefulness of the IPSE chip in dealing with complex matrixes.
Chapter 4 presented an unambiguous distinction between toxic Japanese star anise and non-toxic Chinese star anise fruits within seconds without any sample pretreatment by DART-orbitrap MS technology. Both positive and negative mode gave the same result, although the latter mode is preferred because of its higher sensitivity and cleaner spectra. Not only raw plant materials but also a herbal tea containing both Chinese and Japanese star anise could be quickly and accurately distinguished by DART-HRMS.
In Chapter 5, direct plant spray in combination with orbitrap HRMS allowed, like DART-HRMS, for an unambiguous distinction between toxic Japanese star anise and non-toxic Chinese star anise fruits within seconds without any sample pretreatment in both positive and negative mode. Direct plant spray ionization has the advantage of low cost, simplicity, room temperature and low standard deviations. Neither the DART nor the direct spray method is very suitable for quantitative measurements of solid samples like star anise fruits.
Chapter 6 describes the purification of eight ginkgolic acids (GAs) from raw plant material (Ginkgo biloba) by using only three steps, namely (1) extraction; (2) selective purification by cheap Fe3O4 magnetic nanoparticles (MNPs); (3) preparative HPLC on a C8 column. The three main constituents occurring at concentrations of 0.15% - 0.60% were enriched to >95% absolute purity without using tedious (gravity) column chromatography with halogenated solvents.
Preparative RP-HPLC is an efficient but not very green technique for the final purification of fine chemicals and natural products as large volumes of acetonitrile, methanol and tetrahydrofuran (THF) are consumed. In Chapter 7 it was investigated whether less toxic organic solvents could replace them. As a test case the preparative separation of Ginkgo terpene trilactones (TTLs) was selected. By a two-step chromatographic optimization procedure a 30 min gradient using only water, ethanol, acetone and ethyl acetate was developed, which gave a baseline separation of 480 mg of an injected TTLs mixture. All five individual TTLs were > 95% pure.
Traditional Chinese Medicines (TCMs) are one of the oldest and most used traditional drugs in the world. Many plants are used for their preparation. An overview of HPLC-related methods such as: multicomponent quantitation, fingerprinting, bioaffinity chromatography and on-flow assays for screening and quality control of TCMs was presented and discussed in Chapter 8.
The final Chapter 9 discusses the major findings of this work and gives further perspectives.
|Qualification||Doctor of Philosophy|
|Award date||22 Jun 2015|
|Place of Publication||Wageningen|
|Publication status||Published - 2015|
- poisonous plants
- chemical composition
- mass spectrometry
- nondestructive testing
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11/01/11 → 22/06/15