Abstract View
Optimization Study of a Thermal Ambient Desorption Source to Improve Sensitivity for Fragile Heritage Objects and Conservation
MICHAEL BUCHANAN, Xi Chen, Viraj Gandhi, Asher Newsome, Carlos Larriba-Andaluz, IUPUI
Abstract Number: 420
Working Group: Instrumentation and Methods
Abstract
Ambient desorption/ionization may be combined with a variety of Ion Mobility Spectrometers (IMS) and Mass Spectrometer (MS) systems for analyzing surfaces at atmospheric pressure. A typical sampling system is direct analysis in real time (DART) which uses heated gas flow to thermally desorb analytes for ionization in the gas phase and collection by a vacuum inlet. In a collaboration with the Smithsonian Museum Conservation Institute, this project aims at improving the collection efficiency of particles in a similar system through the study of the thermo-fluid dynamic domain at the sample exposure position including inlet and outlet configurations. The system consists of the outflow tube (a heated capillary with a constant flow rate to extract molecules), sample plate and transfer inlet tube. The collection efficiency is one of the key factors that need improvement, which may be optimized by adjusting the distance and angle of the transfer tube to the sample plate as well as by modifying its geometry and shape. In this project, a series of simulations in nitrogen gas were implemented to study the sample particle trajectories aiming to improve transmission. The model was generated in a computational fluid dynamic (CFD) software SOLIDWORKS, and flow simulations were performed assuming laminar and turbulent flow. Many different configurations are sought by an iterative procedure to optimize the system’s collection efficiency looking at the stream tube that contains the analyte sample and directing it towards the sample inlet. The system is then verified through post-processing simulation of particle tracking. This must be done while meeting some real-life constraints such as keeping an appropriate distance between sample and heated capillary to avoid damage to cultural heritage objects.