Quantification of linolenic acid isomers by gas chromatography‐mass spectrometry and deconvolution of overlapping chromatographic peaks

Abstract

Quantification of linolenic acid isomers by gas chromatography-mass spectrometry and deconvolution of overlapping chromatographic peaksThe use of a technique for deconvolution of overlapping chromatographic peaks, Gentle, has been evaluated for quantification of alpha linolenic acid isomers analysed by gas chromatography-mass spectrometry. Mixtures containing varying amounts of linolenic acid methyl ester isomers with two or three trans double bonds were analysed by two different temperature programs. Overlapping chromatographic peaks were resolved by Gentle, and the areas of the resolved peaks were compared with reference values calculated by use of internal standards. The results show that the small differences that exist between the mass spectra of the analysed isomers are sufficient to achieve deconvolution of severely overlapping peaks. The errors were larger than seen for quantification of chromatographically resolved peaks. Especially for small peaks in a peak cluster, the errors relative to the peak size were large.

Discrimination among geometrical isomers of α-linolenic acid methyl ester using low energy electron ionization mass spectrometry

“…Cis and trans isomers of fatty acids with one or two double bonds differ significantly in polarity but geometrical isomers with three or more double bonds can have very similar polarities. As an example ␣-linolenic acid methyl ester isomers 9-cis, 12-cis, 15-trans, and 9-trans, 12-trans, 15-cis cannot easily be separated by gas chromatography (GC) even using a highly polar column such as BPX-70 [7]. The similarity of isomers and complexity of the chromatograms increase in fatty acids with four, five, and six double bonds giving rise to 16, 32, and 64 geometrical isomers.…”

Adaptation of the Vogt–Mizaikoff F‐test to determine the number of principal factors responsible for a data matrix and comparison with other popular methods

“…In fact, Mjos [9] reports that noise in chromatographic systems is usually heteroscedastic, increasing with signal strength. For this reason we decided to repeat the study described in Table II using a more realistic model that takes this into consideration.…”

“…The eigenvalues in Equation (10) represent the sums of squares of the residual errors. Because Equation (10) involves a much larger number of degrees of freedom than Equation (9), the FK test is much more sensitive to the true distribution of the residual errors. A 1% significance level cut-off criterion for separating the principal factors from the error factors has been recommended.…”

“…The following procedure is used to determine n. First the smallest eigenvalue is assigned to the error pool and the next larger eigenvalue is tested for equality using Equation (9). If it is found to be equivalent, then it is added to the error pool and the next larger eigenvalue is tested for equality.…”

ÁCIDOS GRASOSTRANS: CONSUMO E IMPLICACIONES EN LA SALUD EN NIÑOSTRANSFATTY ACID: INTAKE AND IMPLICATIONS FOR CHILD HEALTH

“…Entre los métodos más utilizados para la cuantificación de AGT en alimentos se encuentran la cromatografía de gases, la cromatografía de gases ligada a espectrometría de masas, la cromatografía en placa fina con plata seguida de cromatografía gaslíquida y la espectroscopia de infrarrojo (Destaillats et al, 2007;Mjøs, 2004;Valenzuela y Morgado, 1999). La confiabilidad de los resultados depende del tipo de análisis utilizado en la determinación.…”