Gas chromatographic quantification of fatty acid methyl esters: Flame ionization detection vs. Electron impact mass spectrometry

Abstract

The determination of FAME by GC is among the most commonplace analyses in lipid research. Quantification of FAME by GC with FID has been effectively performed for some time, whereas detection with MS has been used chiefly for qualitative analysis of FAME. Nonetheless, the sensitivity and selectivity of MS methods advocate a quantitative role for GC-MS in FAME analysis-an approach that would be particularly advantageous for FAME determination in complex biological samples, where spectrometric confirmation of analytes is advisable. To assess the utility of GC-MS methods for FAME quantification, a comparative study of GC-FID and GC-MS methods has been conducted. FAME in prepared solutions as well as a biological standard reference material were analyzed by GC-FID and GC-MS methods using both ion trap and quadrupole MS systems. Quantification by MS, based on total ion counts and processing of selected ions, was investigated for FAME ionized by electron impact. Instrument precision, detection limits, calibration behavior, and response factors were investigated for each approach, and quantitative results obtained by each technique were compared. Although there were a number of characteristic differences between the MS methods and FID with respect to FAME analysis, the quantitative performance of GC-MS compared satisfactorily with that of GC-FID. The capacity to combine spectrometric examination and quantitative determination advances GC-MS as a powerful alternative to GC-FID for FAME analysis.

A GC – magnetic sector MS method for identification and quantification of fatty acids in ewe milk by different acquisition modes

“…These values were further verified by performing SIM analysis of a low-concentration FAME standard mix, the individual FAMEs varied from 30 to 90 ng/mL. The values for the LOD for all the three techniques are significantly lower than those determined by Dodds et al [8], using quadropole MS (scan and SIM mode) and ion-trap MS (scan and RIC mode). This group reported LOD values in the mg/mL region.…”

“…In SIM mode the RSD varied from 0.47 to 3.92%, but only two FAMEs were below 1% RSD. In contrast to this Dodds et al [8], using a quadropole instrument, found better reproducibility for SIM mode than for scan mode. The precision was also tested by the analysis of a FAME standard mixture with a total FAME concentration of 150 mg/mL (the individual FAMEs varied in concentration from 3 to 9 mg/ mL) and the IS concentrations were 5 mg/mL.…”

“…FAME analysis based on SIM ions from the low m/z region (m/z 45-100) have previously been successfully performed [8,9]. We wanted to use SIM ions from the upper m/z region.…”

“…The by far most common detector in the analysis of FAMEs has been the flame ionization detector [6,7]. The complexity of biological samples limits the usefulness of this detector, since the only information gathered is retention time and instrument response [8]. Using an MS as a detector increases the sensitivity and the selectivity of the analytical method, since this detector also provides important spectrometric information on the separated compounds [8,9].…”

“…The complexity of biological samples limits the usefulness of this detector, since the only information gathered is retention time and instrument response [8]. Using an MS as a detector increases the sensitivity and the selectivity of the analytical method, since this detector also provides important spectrometric information on the separated compounds [8,9]. The sensitivity can normally be further improved by the use of SIM or reconstructed ion chromatogram (RIC).…”