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Title: Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions

Abstract

A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography–flame ionization detection, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HClmore » to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.« less

Authors:
; ;
Publication Date:
Research Org.:
National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States). In-house Research
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1129887
Report Number(s):
A-CONTR-PUB-019
DOE Contract Number:  
DE-FE0004000
Resource Type:
Journal Article
Journal Name:
JOURNAL OF CHROMATOGRAPHIC SCIENCE
Additional Journal Information:
Journal Volume: 50; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Kail, Brian W, Link, Dirk D, and Morreale, Bryan D. Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions. United States: N. p., 2012. Web. doi:10.1093/chromsci/bms093.
Kail, Brian W, Link, Dirk D, & Morreale, Bryan D. Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions. United States. doi:10.1093/chromsci/bms093.
Kail, Brian W, Link, Dirk D, and Morreale, Bryan D. Thu . "Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions". United States. doi:10.1093/chromsci/bms093.
@article{osti_1129887,
title = {Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions},
author = {Kail, Brian W and Link, Dirk D and Morreale, Bryan D},
abstractNote = {A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography–flame ionization detection, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HCl to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.},
doi = {10.1093/chromsci/bms093},
journal = {JOURNAL OF CHROMATOGRAPHIC SCIENCE},
number = 10,
volume = 50,
place = {United States},
year = {2012},
month = {11}
}