Chemical Analysis by Sessile Droplet Microfluidic Devices and Surface Sampling Probe Mass Spectrometry

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Hermann, Matthias
Mass Spectrometry , Analytical Chemistry , Microfluidics , Electrospray Ionization , Mass Spectrometry Imaging , Spectrometer , Surgery , Perioperative , Automation
Is this tissue section cancerous or benign? Is this water safe to drink? Is the concentration of red blood cells in this sample sufficient? Those are just a few of many questions that the instrumentation, devices and methods developed within this thesis attempt to answer. Numerous quantitative and qualitative analytical chemistry techniques are utilized in billions of tests daily to answer a wide range of questions. Some methods require highly experienced personnel and advanced infrastructure, while others are cost-effective, portable, and easy to perform. With the COVID-19 pandemic, people worldwide became familiar with different types of tests to determine whether an individual is infected. Rapid antigen tests are examples of fast, portable, and easy to use microfluidic devices but provide limited sensitivity and accuracy. First microfluidic devices that also allow for fast and easy-to-use “point-of-care” (PoC) analysis are described, such as a sessile droplet microfluidic device to analyze cadmium in drinking water. The concept is extended with a microfluidic chip using fluid motion based on Young-Laplace-forces for viscosity measurements. Some analyses lend themselves to simple devices. However, more complex determinations and enhanced instrumentation can improve accuracy and sensitivities but require advanced laboratory equipment. An approach to reduce the costs of such tests while maintaining their accuracy and sensitivity is by increasing sample throughput and reducing the required personnel by automation of sample preparation and analysis. A self-built sampling stage for automated profiling of surfaces and its utility by chemically profiling cancerous kidney and liver tissue samples in conjunction with a surface sampling probe coupled to a mass spectrometer is presented. Lastly, the rapid surface wetting and droplet deposition devices are combined with the automated sampling stage. A microfluidic approach is employed that uses discontinuous dewetting to accurately deposit and position droplets of defined volume on a calibration slide. The calibration slide can be prepared in seconds, eliminating the need to pipette and prepare many calibration solutions.
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