Miniature Mass Spectrometer System with a Sampling Probe
This thesis focuses on the development of miniature mass spectrometry systems and the sampling probes. Mass spectrometers are usually installed and used in the analytical laboratory. It requires complex sample preparation before the analysis. Use of miniature mass spectrometer enables the chemical analysis outside the lab and a sampling probe provides convenience for real-time analysis. Two miniature mass spectrometer systems have been developed in this work.^ A backpack mass spectrometer with a handheld probe was designed for on-site forensic analysis. The handheld probe consists of a mass analyzer, high vacuum pump, and in-line low temperature plasma (LTP) source. The wearable backpack unit contained other components can be easily carried by the user. A miniature pumping system with a 130g drag pump and a 350g scroll pump was used in this system. Direct surface analysis of illicit drug and explosives in tens of nanogram was demonstrated.^ Another portable mass spectrometer with a remote sampling probe was designed for in vivo tissue analysis in surgical and endoscopic procedures. The remote sampling probe has a dual-channel configuration, with one channel (0.5mmID) for providing the desorption spray, and one channel (1.5m-long, 1.6mmID) for guiding the charged species back to the mass spectrometer. No high voltage was applied to generate the spray and pure water was used as the solvent for compatibility with medical operation. The sensitivity of the whole system was improved by efficient desolvasion using a heated capillary and ion accumulation with multiple ion introductions. Lipid profiles of high signal to noise ratio have been obtained from direct analysis of rat brain, liver, lung, and intestine tissue sections on this platform. The compatibility of this system would allow it be used in the operating surgical room to provide molecular information that potentially could guide the surgeons to make a prompt decision during the surgery. Other applications such as a quick screening of chemicals on a Pelican case and aging study of pen ink were also demonstrated. ^
Zheng Ouyang, Purdue University.
Analytical chemistry|Biomedical engineering