Development of an in situ and mobile mass spectrometer for environmental and medical analysis.

摘要

Applications of analytical chemistry and novel trace-gas detection techniques permit new insights into environmental chemistry and human biology. My dissertation involves the theoretical, methodological and experimental development of analytical techniques to measure several such significant compounds. The focus of the doctoral work was the construction of a portable Time-of-Flight Mass Spectrometer (TOF-MS) using Resonance Enhanced Multi-Photon Ionization (REMPI) for compound selectivity. Two general types of light sources are used for ionization: excimer lasers (KrF*, XeCl* and ArF*) and Nd:YAG lasers. The two tuneable light sources used are an excimer-umped dye laser and an Optical Parametric Oscillator (OPO) - Nd:YAG laser system made at our laboratory. Several applications of gas analysis are presented to illustrate the use of this instrument and technique in both the fields of environmental research and medicine. Example compounds are: formaldehyde (HCHO), nitric oxide (NO), nitrogen dioxide (NO2) and aromatic hydrocarbons, such as benzene (C6H6). Presented here are the REMPI-MS techniques designed by our group for simultaneous NO and NO quantification, as well as a new REMPI-MS technique for the detection of HCHO and longer normal-chain aldehydes. The applicability of a commercially-available chemical HCHO analyzer to quantify HCHO in urine was also studied. A comparison of contemporary HCHO analyzers was performed in cooperation with other research groups to verify the agreement among these atmospheric techniques. This study indicates that atmospheric measurements of HCHO using the chemical technique are accurate.