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PhD student's success at the Mass Spectrometry LC-MS Unit
Author: E Els
Published: 19/10/2021

​​​​Keabetswe Masike was a PhD student under the supervision of Prof Marietjie Stander, manager of the Mass Spectrometry LC-MS Unit and Prof André de Villiers of Chemistry, and finished her PhD study successfully in 2021. She relied largely on the CAF LC-MS facilities.

Keabetswe Masike

Keabetswe Masike's research project focused on characterising plant phenolic compounds based on their liquid chromatography-photodiode array-ion mobility-high resolution mass spectrometry (LC-PDA-IM-HR-MS) methods. The compounds were then characterised based on the retention time, mass spectral information (including high resolution and tandem MS data), spectroscopic data and collision cross section (CCS) value data.

Masike decided to embark on this research because the CCS as a feature can be beneficial in the development of an in-house phenolics compound library in analytical laboratories, which can help to expedite the characterisation of phenolic com­pounds in varying research fields, such as plant metabolomics and food science. 

Four Protea plants, comprising two hybrid cultivars and two pure species were collected from the commercial farm “FynBloem" and from the Harold Porter National Botanical Garden respectively for this study. As her research focused on optimising chromatographic and mass spectro­metric (LC-MS) methods for the analyses of a range of plant metabolites, this meant that most of her PhD studies required the LC-MS lab. Some plant metabolites isomerise, making it difficult to differentiate by MS. Thus, the integration of IMS into MS has become an appealing tool for the analyses of structurally similar metabolites. 

Some interesting discoveries were made:

The black beard of the flower head gets its colour from anthocyanidins, the same compounds that is responsible for the colors of berries and red wine.  The concen­trations of these red pigments are so high that they appear black.

The post harvest problem of leaf browning that cause losses especially in the export market was studied. The species and hybrids that are more prone to blackening have differences in their phenolic profiles compared to the species and hybrids that are not.

“The LC-MS lab staff were quite helpful. The collective knowledge regarding sample preparation, LC-MS analyses and data processing has been helpful for the progression of my research work.  As most of my PhD studies involved the analysis of plant extracts using the LC-MS lab, I was able to obtain advice from the staff regarding which options were available to me regarding sample preparation, LC-MS analyses and data processing."

Masike submitted and defended her thesis successfully. Her future plans involve being a committed researcher and an effective educator with a fascination for solving challenging problems in the biological sciences using analytical instrumentation. ​

The original article with images and more detail is published in the 2020-2021 CAF Annual Report.