In situ mass spectrometry
Abstract
Mass spectrometers offer a powerful combination of speed, sensitivity, versatility, and high information content. There is an increasing need for chemical instrumentation that can be utilized in situ for applications such as transportation security, industrial hygiene, environmental monitoring, and astrobiology. Mass spectrometry (MS) has so far been limited to the laboratory setting largely due to the high vacuum conditions required for ion generation and ion processing. This research has developed methods that extend the utility of mass spectrometry to field analysis. In situ MS requires ions to be generated and processed simultaneously without extensive sample preparation. To achieve this end, two parallel approaches are utilized: (1) application of ambient pressure ionization and (2) development of instrumentation capable of portable mass analysis. The initial approach toward in situ MS focused on developing a large area ambient ionization source based on desorption electrospray ionization (DESI) model. The source was designed so that a much larger surface area (∼4 cm2) could be interrogated instantly for a more representative analysis. Trace detection was achieved from a much larger area using wipe analysis; 100 ng of explosive residue was detected over an area of 1 m2 using tandem MS. The applicability of ambient ionization in the field is limited by the immobility of the MS system conducting mass analysis. In situ MS analysis requires portable mass analysis capability. To achieve this end, a miniature MS system was built and developed for use with ambient ionization. Two such ambient ionization methods, low temperature plasma (LTP) and paper spray (PS), were used to detect agrochemicals from the surfaces of fruits at a local grocery store using the Mini MS. A handheld LTP source was used to detect diphenylamine directly from the skin of apples, and thiabendazole residues were detected on the skin of treated oranges using PS ionization.
Degree
Ph.D.
Advisors
Cooks, Purdue University.
Subject Area
Chemistry|Analytical chemistry
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