| Title: | Production of isotopically labeled standards from a uniformly labeled precursor for quantitative volatile metabolomic studies |
| Author(s): | Gomez-Cortes P; Brenna JT; Sacks GL; |
| Address: | "Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA" |
| ISSN/ISBN: | 1520-6882 (Electronic) 0003-2700 (Print) 0003-2700 (Linking) |
| Abstract: | "Optimal accuracy and precision in small-molecule profiling by mass spectrometry generally requires isotopically labeled standards chemically representative of all compounds of interest. However, preparation of mixed standards from commercially available pure compounds is often prohibitively expensive and time-consuming, and many labeled compounds are not available in pure form. We used a single-prototype uniformly labeled [U-(13)C]compound to generate [U-(13)C]-labeled volatile standards for use in subsequent experimental profiling studies. [U-(13)C]-alpha-Linolenic acid (18:3n-3, ALA) was thermally oxidized to produce labeled lipid degradation volatiles which were subsequently characterized qualitatively and quantitatively. Twenty-five [U-(13)C]-labeled volatiles were identified by headspace solid-phase microextraction-gas chromatography/time-of-flight mass spectrometry (HS-SPME-GC/TOF-MS) by comparison of spectra with unlabeled volatiles. Labeled volatiles were quantified by a reverse isotope dilution procedure. Using the [U-(13)C]-labeled standards, limits of detection comparable to or better than those of previous HS-SPME reports were achieved, 0.010-1.04 ng/g. The performance of the [U-(13)C]-labeled volatile standards was evaluated using a commodity soybean oil (CSO) oxidized at 60 degrees C from 0 to 15 d. Relative responses of n-decane, an unlabeled internal standard otherwise absent from the mixture, and [U-(13)C]-labeled oxidation products changed by up to 8-fold as the CSO matrix was oxidized, demonstrating that reliance on a single standard in volatile profiling studies yields inaccurate results due to changing matrix effects. The [U-(13)C]-labeled standard mixture was used to quantify 25 volatiles in oxidized CSO and low-ALA soybean oil with an average relative standard deviation of 8.5%. Extension of this approach to other labeled substrates, e.g., [U-(13)C]-labeled sugars and amino acids, for profiling studies should be feasible and can dramatically improve quantitative results compared to use of a single standard" |
| Keywords: | Alkanes/isolation & purification/metabolism Analytic Sample Preparation Methods/*standards Calibration Gas Chromatography-Mass Spectrometry Isotope Labeling Limit of Detection Metabolomics/*standards Oxidation-Reduction Reference Standards Solid Phase Mic; |
| Notes: | "MedlineGomez-Cortes, Pilar Brenna, J Thomas Sacks, Gavin L eng R01 GM103437/GM/NIGMS NIH HHS/ R01 RR031264/RR/NCRR NIH HHS/ GM10343/GM/NIGMS NIH HHS/ RR031264/RR/NCRR NIH HHS/ Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't 2012/06/06 Anal Chem. 2012 Jun 19; 84(12):5400-6. doi: 10.1021/ac300933d. Epub 2012 Jun 4" |
