Microfluidic based injection systems for capillary electrophoresis coupled to contactless conductivity, fluorescence and mass spectrometric detection

Furter, Jasmine. Microfluidic based injection systems for capillary electrophoresis coupled to contactless conductivity, fluorescence and mass spectrometric detection. 2022, Doctoral Thesis, University of Basel, Faculty of Science.


Official URL: https://edoc.unibas.ch/88826/

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This thesis focuses on the development of novel injection systems for capillary electrophoresis based on microfluidics driven through pressurization combined to different detection methods as well as the coupling to and the use of different ionization methods for mass spectrometry. At first, an ambient ionization method based on a cold plasma, which is called dielectric barrier discharge, was coupled to a mass spectrometer. The ambient plasma source was low-cost and the circuitry can easily be replicated. The plasma source was characterised in terms of electronic and optical properties. The ionization method was used to qualitatively and quantitatively analyse substances from different application areas such as pharmaceuticals, illegal drugs and food samples. As second project a new capillary electrophoresis system based on microfluidics was developed. The injection system was solely based on the application of one fixed pressure, while the flow rates were varied by the implementation of flow restrictors. The feasibility of the instrument was demonstrated by the fast separation of different inorganic cations using a thin capillary with an inner diameter of 10 μm. Nine ions were separated in only 25 seconds. Good reproducibility and detection limits could be achieved.
The third project was the development of a graphical user interface for controlling analytical instruments. The software was written in Java programming language and enables the communication with a microcontroller running Forth code. The graphical user interface sends commands in the interpreted programming language Forth to the microcontroller. This approach is simple and improves at the same time the user friendliness of the device operation. This project was published as part of a tutorial about the usage of Forth on microcontrollers for controlling analytical instruments. The graphical user interface was tested by reading and saving analogue values from an alcohol sensor as well as displaying the results in a real time graph.
The fourth project was the development of a low-cost fluorescence detector for capillary electrophoresis. The detector based on a laser diode was assembled from different commercially available parts. The focused light was coupled to the separation capillary and the arising fluorescence converted to a current by using a photomultiplier. The resulting current was amplified and converted to a voltage by using a transimpedance amplifier. The performance of the detector was demonstrated in the scope of a collaboration with the group of Prof. Dr. Than Duc Mai. A new method was developed for detecting different oligosaccharides labelled with a fluorescent tag by using the detector. The results were compared to the performance of a commercially available instrument.
In the scope of the fifth project, an open source capillary electrophoresis instrument was developed. The design of the instrument was kept as simple as possible. Three modules contained an electronic part for instrument control, a pneumatic part for driving the liquids in the tubes at controlled flow rates and a microfluidic part responsible for all fluid handling actions necessary for sample injection. The performance of the instrument was demonstrated showing the separation of alkaline, alkaline earth metals and different heavy metals. In addition, a method was developed for separating different inorganic ions responsible for honey quality. Four honey samples were analysed quantitatively. This project resulted in a collaboration with the company SensorFactory in the Netherlands.
The last project was the development of an automated capillary electrophoresis instrument for the coupling to a mass spectrometer by using an interface free sheathless nanoelectrospray. The microfluidic part responsible for sample injection contained no electronics to avoid damage of the devices due to the high voltage applied to the injection end. Instead, pneumatic valves and different pressures were used for the injection process. A capillary with an internal diameter of 15 $\mu m$ was employed for obtaining good resolution. Volatile buffers based on acetic acid were used to achieve acceptable separation and ionization of the analytes. The feasibility of the set-up was demonstrated by separating three benzalkonium chloride homologues qualitatively. Good resolution and detection limits were obtained for the quantitative measurements of four pesticides in spiked grape juice.
Advisors:Hauser, Peter C. P. C. and Häussinger, Daniel and Rudaz, Serge
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Analytische Chemie (Hauser)
UniBasel Contributors:Häussinger, Daniel
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:14760
Thesis status:Complete
Number of Pages:xi, 159
Identification Number:
  • urn: urn:nbn:ch:bel-bau-diss147609
edoc DOI:
Last Modified:27 Jul 2022 14:35
Deposited On:26 Jul 2022 14:02

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