Thesis of Vikas Madhur

Defense of thesis Vikas Madhur - laboratory PhLAM

Abstract :

Conventionnal MS techniques, which operate under high vacuum, pose challenges in sample preparation and handling, particularly for environmental samples. To address these issues, this research focuses on designing and optimizing a sampling interface that facilitates the transfer of samples from atmospheric pressure to a vacuum environment for MS analysis. The study employs Two-Step Laser Mass Spectrometry (L2MS) as the primary analytical techniques. L2MS, known for its high sensitivity and selectivity, couples laser desorption and laser ionization with Time-of-Flight (ToF) mass spectrometry, allowing precise analysis of chemical compositions. Raman Spectroscopy complements this by providing detailed vibrational information about the samples. The research explores various configurations for the sampling interface, testing their effectiveness in transferring both liquid and solid samples. For liquid samples, two configurations with single valves are compared, while for solid samples, five different setups involving one and two valves are evaluated. These configurations are assessed based on their ability to transfer molecules efficiently into the vacuum chamber for MS analysis. This work demonstrates the ability of the interface to analyze various model samples, in particular Polycyclic Aromatic Hydrocarbons (PAH). The study also highlights the importance of heating and synchronization between the desorption, valve opening and ionization processes in order to optimize performance, limit pollution of the vacuum chamber and reduce transfer losses. This thesis also contributes to the validation of a technique for debrominating plastic samples containing brominated flame retardants, with a view to their recycling and recovery. For this purpose, the spectra obtained using the atmospheric pressure sampling interface will be compared with the state-of-the-art vacuum analysis system available in the laboratory.

Keywords : mass spectrometry,laser ionization,laser desorption,atmospheric pressure sampling interface,Raman Spectroscopy,brominated plastics