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Trace-Level Volatile Quantitation by DART-MS following Headspace Extraction – Optimization and Validation in Grapes Jillian A. Jastrzembski, Madeleine Y Bee, and Gavin L. Sacks J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b03638 • Publication Date (Web): 02 Oct 2017 Downloaded from http://pubs.acs.org on October 7, 2017
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Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
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Journal of Agricultural and Food Chemistry
TITLE: Trace-Level Volatile Quantitation by DART-MS following Headspace Extraction – Optimization and Validation in Grapes
AUTHORSHIP Jillian A. Jastrzembski, Madeleine Y. Bee, Gavin L. Sacks* Department of Food Science, Stocking Hall, Cornell University, Ithaca, New York 14853 *Author to whom correspondence should be addressed [e-mail
[email protected]; telephone (607-255-2335)]
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Journal of Agricultural and Food Chemistry
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ABSTRACT
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Ambient Ionization – Mass Spectrometry (AI-MS) techniques like Direct Analysis in Real Time
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(DART) offer the potential for rapid quantitative analyses of trace volatiles in food matrices, but
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performance is generally limited by the lack of pre-concentration and extraction steps. The
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sensitivity and selectivity of AI-MS approaches can be improved through solid-phase
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microextraction (SPME) with appropriate thin-film geometries, e.g. solid phase mesh enhanced
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sorption from headspace (SPMESH). This work improves the SPMESH-DART-MS approach for
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use in food analyses, and validates the approach for trace volatile analysis for two compounds in
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real samples (grape macerates). SPMESH units prepared with different sorbent coatings were
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evaluated for their ability to extract a range of odor-active volatiles, with
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polydimethylsiloxane/divinylbenzene giving the most satisfactory results. In combination with
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high-resolution mass spectrometry (HRMS), detection limits for SPMESH-DART-MS under 4
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ng/L in less than 30 s acquisition times could be achieved for some volatiles (3-isobutyl-2-
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methoxypyrazine (IBMP), β-damascenone). A comparison of SPMESH-DART-MS and SPME-
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GC-MS quantitation of linalool and IBMP demonstrates excellent agreement between the two
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methods using real grape samples (r2≥0.90), although linalool measurements appeared to also
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include isobaric interferences.
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Keywords: Low level odorants, volatile analysis, wine grapes, DART, ambient ionization
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Journal of Agricultural and Food Chemistry
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INTRODUCTION
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Ambient ionization mass spectrometry (AI-MS) techniques like direct analysis in real time
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(DART)-MS can improve simplicity and throughput for a wide range of routine chemical
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analyses.1 In comparison to other popular AI approaches, e.g. desorption electrospray ionization
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(DESI), DART is better suited for volatile or semi-volatile low molecular weight compounds (
