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  4. VISUALIZING AROMA: SPATIALLY RESOLVED, HIGH-THROUGHPUT, AND AUTOMATED DETECTION OF ODORANTS IN GRAPES USING AMBIENT IONIZATION MASS SPECTROMETRY

VISUALIZING AROMA: SPATIALLY RESOLVED, HIGH-THROUGHPUT, AND AUTOMATED DETECTION OF ODORANTS IN GRAPES USING AMBIENT IONIZATION MASS SPECTROMETRY

File(s)
DiGregorio_cornellgrad_0058F_11911.pdf (6.63 MB)
Permanent Link(s)
https://doi.org/10.7298/gp6w-3t70
https://hdl.handle.net/1813/70443
Collections
Cornell Theses and Dissertations
Author
DiGregorio, Madeleine
Abstract

This dissertation describes the development and validation of a novel headspace extraction approach for high-throughput analyses of trace-level volatiles. Solid phase mesh enhanced sorption from headspace, or “SPMESH”, consists of a sorbent coated mesh that simultaneously extracts and pre-concentrates volatiles from the headspace of a sample. By laser-etching thin films of polydimethylsiloxane, SPMESH Sheets could be made to fit on multi-well plates. This allowed for extraction and pre-concentration of 24 samples in parallel, followed by automated analysis by Direct Analysis in Real Time mass spectrometry, or DART-MS. Extraction and desorption conditions for SPMESH Sheet-DART-MS were optimized to increase sensitivity, using a response surface methodology experimental design. Gaskets and clamps were created for the extraction setup to reduce headspace cross-contamination between wells, which would artificially increase signal due to volatiles drifting between neighboring wells. Two analytes of interest were profiled in grapes, as markers of final wine flavor: 2-isobutyl-3-methoxypyrazine and linalool. Limits of detection were further improved with the use of high resolution MS for linalool (48 μg/L) and tandem MS for IBMP (4 ng/L). Using these optimized conditions, a multi-vineyard validation was performed using grapes harvested from June – September of 2019. Good correlations were found for both compounds using SPMESH Sheet-DART-MS compared to the standard industry method: SPME-GC-MS. In a separate study, SPMESH Sheets were used for liquid desorption, using only 2 μL droplets to extract the headspace volatiles. This approach expands the range of compounds that can be detected, beyond those compatible with DART-MS. It also improves the spatial resolution of the SPMESH Sheet, previously limited to 4 mm by the DART source, to the size of a 2 μL drop, approximately 0.1 mm. Droplet desorption SPMESH has the possibility to be used in the future for mass spectral imaging studies of volatile and semi-volatile compounds.

Description
90 pages
Date Issued
2020-05
Keywords
direct analysis in real time
•
high-throughput analysis
•
solid phase microextraction
Committee Chair
Sacks, Gavin
Committee Member
Loeb, Gregory
Abbaspourrad, Alireza
Degree Discipline
Food Science and Technology
Degree Name
Ph. D., Food Science and Technology
Degree Level
Doctor of Philosophy
Type
dissertation or thesis
Link(s) to Catalog Record
https://catalog.library.cornell.edu/catalog/13254441

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