Lipids

, Volume 45, Issue 2, pp 199–208

An Improved Method for Determining Medium- and Long-Chain FAMEs Using Gas Chromatography

  • Zhidong Xu
  • Kevin Harvey
  • Thomas Pavlina
  • Guy Dutot
  • Gary Zaloga
  • Rafat Siddiqui
Methods

DOI: 10.1007/s11745-009-3382-7

Cite this article as:
Xu, Z., Harvey, K., Pavlina, T. et al. Lipids (2010) 45: 199. doi:10.1007/s11745-009-3382-7

Abstract

The existing protocols for analyzing fatty acid methyl esters (FAMEs) using a one-step acetyl chloride (AC) catalyzed transesterification and extraction procedure cannot accurately determine the medium- and long-chain fatty acids simultaneously in clinical (enteral, parenteral) formulations. For example: (1) addition of AC at room temperature generates an exothermic reaction that often results in loss of sample and possible injury to the analyst; (2) certain polyunsaturated fatty acids (PUFAs) are less stable at elevated temperatures during the transesterification and contribute to the over-estimation of the C16:0 and C18:1 fatty acids; and (3) the flame-ionization detector (FID) response varies depending on the carbon chain length of the fatty acids, that consequently impacts the underestimation of medium-chain fatty acid (C6–C10) recoveries. To overcome these deficiencies and accurately determine FAMEs, we have developed an improved one-step transesterification method that employs the addition of AC in tubes kept on a dry ice bath, the transesterification at room temperature, and the data analysis using relative response factors. Using this modified protocol, we determined the fatty acid composition of lipid emulsions (Omegaven® and Lipidem®) on a Shimadzu GC2010 gas chromatography (GC) system using a capillary GC column (Zebron ZB-WAX plus, 30 m, 0.25 mm ID, 0.25 μm). Our data suggest that the improved method can be easily used to accurately determine fatty acids (C6–C24) in functional foods and lipid emulsions.

Keywords

Medium-chain fatty acids Long-chain fatty acids Relative response factor Lipid emulsion Transesterification 

Abbreviations

AC

Acetyl chloride

AOAC

Association of Analytical Chemists

Calc.

Calculations

Exp

Experimental

FAME

Fatty acid methyl esters

FAs

Fatty acids

FID

Flame ionization detector

GC

Gas chromatography

IS

Internal standard

PUFAs

Polyunsaturated fatty acids

REF

Relative response factor

Theo

Theoretical

Copyright information

© AOCS 2010

Authors and Affiliations

  • Zhidong Xu
    • 1
  • Kevin Harvey
    • 1
  • Thomas Pavlina
    • 2
  • Guy Dutot
    • 3
  • Gary Zaloga
    • 2
  • Rafat Siddiqui
    • 1
    • 5
    • 4
  1. 1.Methodist Research Institute, Clarian HealthIndiana University School of MedicineIndianapolisUSA
  2. 2.Baxter Healthcare CorporationDeerfieldUSA
  3. 3.Baxter SASMaurepas CedexFrance
  4. 4.Department of MedicineIndiana University School of MedicineIndianapolisUSA
  5. 5.Cellular Biochemistry LaboratoryMethodist Research InstituteIndianapolisUSA

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