Further development of fluorescence excitation spectroscopy

|   Physik, Chemie, Gäste

Philipp Bokatius, Gudrun Mende, Matthias Rang & Peter Stolz

Project status after the project's first year

The research project, which started as a collaboration between the KWALIS GmbH research institute and the research institute at the Goetheanum at the beginning of 2019, deals with the further development of fluorescence excitation spectroscopy. In fluorescence excitation spectroscopy, the fluorescent light of a previously briefly illuminated sample is measured. The method was originally developed by Jürgen Strube some thirty years ago and introduced at the KWALIS GmbH research institute as a method for qualitative research on foodstuffs. Since then, several studies on qualitative differences have been carried out with the original equipment setup by Strube, totalling more than 150,000 series of measurements.

Due to the age of the existing equipment, our primary goal at present is to build a new system. The core technical element of this system is the detector unit, consisting of a photomultiplier that converts the extraordinarily low fluorescence of the sample into an electrical signal. This unit forms the detection path along with the amplifier electronics that amplify the very short electrical counting pulses and the computer interface or counting card that digitally records the pulses. The exact interaction of these components represents the actual heart of the new system where the measurement results are created and documented.

Some unexpected difficulties arose during development and resolving the technical problems took considerably more time than was estimated in the project plan. However, there are indications of an improvement over the existing system that we were not able to fully assess at the time of application. We have only provisionally characterised the detection unit but it looks as if we will achieve many times the count rate of the current equipment with similar increases in dark count rate and absolute sensitivity. The total measuring range of the composite detection unit (the dynamic range) will then also increase by this factor compared to the existing system.

Changed project management and addition of personnel

After the first year we have to report a delay of several months in the construction of the new system. This is not only due to the technical difficulties mentioned above but also to a change in the project management. For example, the change in Section leadership of the Natural Science Section at the Goetheanum from Johannes Kühl to Johannes Wirz and Matthias Rang on the first of January 2020 has necessitated a reduction in Matthias Rang's share of the project's workload. Fortunately, we have been able to recruit a new staff member, Philipp Bokatius, as of autumn 2020, who will be able to primarily take over the task of programming the new system as well as producing the technical CAD drawings for Matthias Rang's mechanical design. Philipp Bokatius brings with him experience in both 3D modelling and programme development, so this addition to the team is extremely promising.

Project perspectives for the second year

We are currently working on completing the CAD drawings for the custom-made mechanical components and completing the control programme. Even after the successful completion of these essential steps there are still important tasks to be done before commissioning of the plant. In addition to the actual mechanical production which we will outsource to a contract milling company, these tasks include developing the cooling management of the photomultipliers, the modular illumination unit and an extensive testing and characterisation phase.