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Anal Chem. 2015 Nov 3;87(21):10935-41. doi: 10.1021/acs.analchem.5b03003. Epub 2015 Oct 14.

Thermal Degradation of Small Molecules: A Global Metabolomic Investigation.

Author information

1
Scripps Center for Metabolomics and Mass Spectrometry, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United States.
2
Metabolomics Platform, Faculty of Biology and Medicine, University of Lausanne , Rue du Bugnon 19, 1011 Lausanne, Switzerland.
3
Department of Chemistry, Washington University in St. Louis , One Brookings Drive, St. Louis, Missouri 63130, United States.
4
Departments of Chemistry, Molecular and Computational Biology, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United States.

Abstract

Thermal processes are widely used in small molecule chemical analysis and metabolomics for derivatization, vaporization, chromatography, and ionization, especially in gas chromatography mass spectrometry (GC/MS). In this study the effect of heating was examined on a set of 64 small molecule standards and, separately, on human plasma metabolite extracts. The samples, either derivatized or underivatized, were heated at three different temperatures (60, 100, and 250 °C) at different exposure times (30 s, 60 s, and 300 s). All the samples were analyzed by liquid chromatography coupled to electrospray ionization mass spectrometry (LC/MS) and the data processed by XCMS Online ( xcmsonline.scripps.edu ). The results showed that heating at an elevated temperature of 100 °C had an appreciable effect on both the underivatized and derivatized molecules, and heating at 250 °C created substantial changes in the profile. For example, over 40% of the molecular peaks were altered in the plasma metabolite analysis after heating (250 °C, 300s) with a significant formation of degradation and transformation products. The analysis of 64 small molecule standards validated the temperature-induced changes observed on the plasma metabolites, where most of the small molecules degraded at elevated temperatures even after minimal exposure times (30 s). For example, tri- and diorganophosphates (e.g., adenosine triphosphate and adenosine diphosphate) were readily degraded into a mono-organophosphate (e.g., adenosine monophosphate) during heating. Nucleosides and nucleotides (e.g., inosine and inosine monophosphate) were also found to be transformed into purine derivatives (e.g., hypoxanthine). A newly formed transformation product, oleoyl ethyl amide, was identified in both the underivatized and derivatized forms of the plasma extracts and small molecule standard mixture, and was likely generated from oleic acid. Overall these analyses show that small molecules and metabolites undergo significant time-sensitive alterations when exposed to elevated temperatures, especially those conditions that mimic sample preparation and analysis in GC/MS experiments.

PMID:
26434689
PMCID:
PMC4633772
DOI:
10.1021/acs.analchem.5b03003
[Indexed for MEDLINE]
Free PMC Article

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